                 System           Support            Addendum  J           ________________________________________________________________  K           PRODUCT NAME:  VAX Packetnet System Interface     SSA 25.40.15-A  .                          (P.S.I.), Version 4.3             HARDWARE REQUIREMENTS              Processors Supported:   '           VAX:      VAX 4000 Model 300,   .           VAX:      VAX 6000 Model 200 Series,.                     VAX 6000 Model 300 Series,-                     VAX 6000 Model 400 Series   ;                     VAX 8200, VAX 8250, VAX 8300, VAX 8350, ;                     VAX 8500, VAX 8530, VAX 8550, VAX 8600, ;                     VAX 8650, VAX 8700, VAX 8800, VAX 8810, ;                     VAX 8820, VAX 8830, VAX 8840, VAX 8842, &                     VAX 8974, VAX 8978  B                     VAX-11/730, VAX-11/750, VAX-11/780, VAX-11/785  /           MicroVAX: MicroVAX II, MicroVAX 2000, 1                     MicroVAX 3100, MicroVAX 3300, 1                     MicroVAX 3400, MicroVAX 3500, 1                     MicroVAX 3600, MicroVAX 3800, !                     MicroVAX 3900   5           VAXstation: VAXstation II, VAXstation 3200, 7                       VAXstation 3500, VAXstation 3520,       J                                        DIGITAL                   July 1990  J                                                                AE-LP46C-TE         J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3         #                     VAXstation 3540   4           VAXserver: VAXserver 3100, VAXserver 3300,4                      VAXserver 3400, VAXserver 3500,4                      VAXserver 3600, VAXserver 3602,3                      VAXserver 3800, VAXserver 3900   <                      VAXserver 6000-210, VAXserver 6000-310,;                      VAXserver 6000-410, VAXserver 6000-420   #           Processors Not Supported:              MicroVAX: MicroVAX I    L           VAXstation: VAXstation I, VAXstation 2000, VAXstation 3100 Series,%                       VAXstation 8000   +           VAX:      VAX- 11/725, VAX-11/782               Processor Restrictions  3           o  At least 1.5M bytes of physical memory   8           o  Non-paged dynamic pool computed as follows:                At least:  G              -  60K bytes for the VAX P.S.I. software and data storage,                  plus  E              -  13K bytes if the VAX P.S.I. X.29 capabilities are re-                  quired, plus  0              -  1K byte for each local DTE, plus      +                                           2        J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3       C              -  1.5K bytes for each virtual circuit, calculated as:   <                 <WINDOWSIZE>*<packetsize + 96>*2 + 700 bytes  :                 charged to the quota of the using process.  G           o  Paged dynamic pool - VAX P.S.I. requires 50 bytes for each @              entry defined in the system DTE logical name table.              Communications Devices  I           One of the following communications devices is required for use            with VAX P.S.I.:  G           o  The KMS1P-A, KMS1P-B and KMS11-B (UNIBUS) products are DMA J              devices. The KMS communications controller executes characterG              transmission, reception, and X.25 data link level protocol G              processing in microcode (LAPB only, for packets not larger I              than 1024 bytes). The VAX CPU then processes the X.25 packet F              level protocol. Optional link-level software products andF              tools available for the KMS devices are not required. TheJ              KMS1P-A and KMS1P-B were previously known as the KMS11-PX and              KMS11-PY.                                +                                           3      J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3         G              In the case of the KMS11-B eight-line device, all lines in I              use must be connected to the same network and must be in the $              same mode (DTE or DCE).  I           o  The DUP11 (UNIBUS) and DPV11-DA or DPV11-S (Q-bus) are char- H              acter interrupt devices for LAPB or LAPBE datalink handlingH              where CPU cycles are required for X.25 packet and data linkG              level protocol processing, and for each character sent and               received.  E           o  The DMF32 (UNIBUS) and DMB32 (BI-BUS) are multi-function H              devices which include a single DMA line. The communicationsG              controllers perform character transmission, reception, and F              HDLC framing in microcode. The VAX CPU then processes theG              X.25 data link (LAPB or LAPBE) and packet level protocols.   J              In the case of the DMF32, only rev. J and later are supportedE              with the VAX P.S.I. software, and rev. M is required for H              simultaneous operation of the printer port with VAX P.S.I...              For the DMB32, rev.J is required.  H           o  The DST32 (Busless) is a single line synchronous communica-G              tions device for the MicroVAX 2000. The DST32 supports DMA E              transfers for bit oriented protocols. The communications G              controller performs character transmission, reception, and F              HDLC framing in the microcode. The MicroVAX 2000 CPU thenJ              processes the X.25 data link (LAPB or LAPBE) and packet level              protocols.   G           o  The DSH32 (Busless) is a multi-function device for the Mi- F              croVAX 2000 and MicroVAX 3100 which includes a single DMAJ              line. The communications controller performs character trans-G              mission, reception, and HDLC framing in microcode. The Mi- I              croVAX CPU then processes the X.25 data link (LAPB or LAPBE) (              and packet level protocols.      +                                           4        J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3     F           o  The KMV1A-A or KMV1A-SF (Q-bus) communications controllerG              executes transmission, reception, and X.25 link level pro- F              tocol processing in microcode (LAPB only, for packets notI              larger than 1024 bytes). The VAX CPU then processes the X.25 F              packet level protocol. Optional link-level software prod-I              ucts, drivers and tools, available for the KMV1A device, are G              not required. The KMV1A device was previously known as the               KMV11-A.   H           o  The DSV11 (Q-bus) is a dual line synchronous communicationsG              device for Q-bus systems. The DSV11 supports DMA transfers E              for bit and character oriented protocols. The communica- I              tions controller performs character transmission, reception, F              and HDLC framing in the microcode. Then, the VAX CPU pro-G              cesses the X.25 data link (LAPB or LAPBE) and packet level               protocols.   H           o  The DIV32 (Q-bus) is a single board, Basic Rate Access com-F              munications device for Q-bus MicroVAX systems running VAXI              ISDN software. The DIV32 supports one ISDN Basic Rate Access F              connection, providing two 64K bps bearer (B) channels forI              data transfer and one 16K bps (D) channel for signaling. The G              VAX ISDN software can establish a connection through the D I              channel, allowing VAX P.S.I. to establish an X.25 connection J              and transfer data via a B channel. Refer to VAX ISDN SoftwareJ              Product Description (SPD 31.23.xx) for more information about-              VAX ISDN software and the DIV32.   I           o  The DSB32 (BI-bus) is a dual line synchronous communications G              device for VAXBI systems. The DSB32 supports DMA transfers I              for bit and character oriented protocols. The communications G              controller performs character transmission, reception, and J              HDLC framing in the microcode. The VAX CPU then processes theG              X.25 data link (LAPB or LAPBE) and packet level protocols.   G           Refer to Table 2 for details of processor and device combina- ;           tions and configuration guidelines for VAX P.S.I.   "           Block Space Requirements  +                                           5      J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3       <           Block Space Requirements (Block Cluster Size = 1):  4           Disk space required for       6,000 Blocks4           installation:                 (3.1M bytes)  4           Disk space required for       8,000 Blocks4           use (permanent):              (4.1M bytes)  E           These counts refer to the disk space required on the system G           disk. The sizes are approximations; actual sizes may vary de- F           pending on the user's system environment, configuration, and$           software options selected.  G           For VAX P.S.I. operating in multi-host mode, the system must, D           in addition, meet the requirements for DECnet-VAX; consultD           the DECnet-VAX Software Product Description (SPD 25.03.xx)G           for a complete description of that product's minimum hardware            requirements.              OPTIONAL HARDWARE   H           Additional communications device(s) subject to the limitationsF           described in Table 2 of this System Support Addendum are re-           quired.              CLUSTER ENVIRONMENT   G           This layered product is fully supported when installed on any I           valid and licensed VAXcluster * configuration. The HARDWARE RE- I           QUIREMENTS sections of this product's Software Product Descrip- F           tion and System Support Addendum detail any special hardware#           required by this product.   F           * V5.x VAXcluster configurations are fully described in VAX-I           cluster Software Product Description (29.78.xx) and include CI, 9           Ethernet and Mixed Interconnect configurations.       +                                           6        J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3     F           On common disks, in order to configure some product specificD           attributes that must remain unique to each system, certainE           components of the product are stored in the system specific E           environment (SYS$SPECIFIC: [SYSxxx]) of the VAX computer on I           which the installation is being performed. The remaining compo- G           nents of the product, including some or all of the executable H           images, will be installed common to all accessing VAX systems.  D           Though some or all of the product's executable images willD           exist in the common system directory (SYS$COMMON:[SYSEXE])H           and be executable by all VAX computers sharing this directory,E           it is essential that the product be installed separately on F           all VAXcluster or Local Area VAXcluster licensed VAX systemsI           requiring access in order to uniquely configure the product for            each.   G           The same version of VAX P.S.I. must be used on all systems in F           VAXcluster systems accessing a common disk and in Local Area$           VAXcluster configurations.             SOFTWARE REQUIREMENTS   2           VMS Operating System V5.1, V5.2 or V5.3.  H           For VAX P.S.I. Multi-host mode, or for any use of DECnet (DLM)H           circuits over a PSDN(s), DECnet-VAX V5.1, V5.2 or V5.3 (eitherI           end-node or full-function) is required (refer to SPD 25.03.xx).   E           For use with the synchronous communications interfaces, the G           appropriate device driver in the VAX Wide Area Network Device D           Drivers V1.1 software is required (refer to SPD 29.64.xx).  I           For use with the DIV32 Basic Rate Access communications device, E           VAX ISDN V1.0 software is required (refer to SPD 31.23.xx).              VMS Tailoring   G           For VMS V5.x, the following VMS classes are required for full 0           functionality of this layered product:  !           o  VMS Required Saveset   +                                           7          J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3                  o  Network Support             o  Utilities              o  Programming Support              o  Bliss Require Files  *           o  User Environment Test Package  I           For more information on VMS classes and tailoring, refer to the J           VMS Operating System Software Product Description (SPD 25.01.xx)             OPTIONAL SOFTWARE   )           For VAX P.S.I. Multi-host mode:   I           DECnet-VAX V5.1, V5.2 or V5.3 either full-function or end-node.   E           If you have more than one VAX P.S.I. Multi-host node, users H           in one Multi-host node can gain access to PSDN(s) connected toJ           another Multi-host node if both VAX P.S.I. and VAX P.S.I. Access)           are installed on the same node.   H           Certain versions of these products depend upon a specific ver-J           sion of the operating system. Please refer to the System SupportF           Addendum (SSA) of the product in question to determine which           version is required.             GROWTH CONSIDERATIONS   H           The minimum hardware/software requirements for any future ver-H           sion of this product may be different from the requirements of           the current version.             DISTRIBUTION MEDIA  B           Tape: 9-track 1600 BPI Magtape (PE), TK50 Streaming Tape  H           This product is also available as part of the VMS Consolidated)           Software Distribution on CDROM.              ORDERING INFORMATION  +                                           8      J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3         (           Software Licenses: QL-071A*-**%           Software Media: QA-071A*-** -           Software Documentation: QA-071AA-GZ 0           Software Product Services: QT-071A*-**    I           *  Denotes variant fields. For additional information on avail- H              able licenses, services and media, refer to the appropriate              price book.  #           Supported Public Networks   E           Table 1 describes public PSDNs which are supported with VAX H           P.S.I. only in the countries shown. Connections to public net-J           works outside this list are customer supported only. In additionG           to these public PSDNs, certain private PSDNs have been tested H           by Digital and appropriate profiles included in the VAX P.S.I.           product.  J           Since the publication of this SPD, other configurations may haveG           been tested. Please consult your local Digital office for any 2           questions concerning other public PSDNs.  J           ________________________________________________________________  ,                                     Table 1:2                          Supported Public Networks  G                                        Public Network          Comments F                                        and CCITT revi-         and Re-I           Country                      sion(s)                 strictions   ,           Argentina                    Arpac  .           Australia                    Austpac  .           Austria                      Datex-P  *           Belgium                      DCS  +                                           9      J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3     1                                  Table 1: (Cont.) 2                          Supported Public Networks  G                                        Public Network          CommentsdF                                        and CCITT revi-         and Re-I           Country                      sion(s)                 strictions     -           Brazil                       Renpac,  7           Canada                       Datapac (1976 or ,                                        1980)  1                                        Infoswitch0  .           Denmark                      Datapak  4           Ireland                      Eirpac (1980)  .           Finland                      Datapak  /           France                       Transpac0  .           Hong Kong                    Datapak  /                                        Intelpak   +           Indonesia                    SKDP   -           Italy                        Itapac   I           Japan                        DDX (1976, 1980)        See Note 1   5                                        Venus-P (1980)   -                                        Tymnet         +                                          10     r    1                                  Table 1: (Cont.)X2                          Supported Public Networks  G                                        Public Network          Comments F                                        and CCITT revi-         and Re-I           Country                      sion(s)                 strictionsP  -           Luxembourg                   LUXPACm  -           Malaysia                     Maypac   .           Mexico                       Telepac  0           Netherlands                  Datanet 1  -           New Zealand                  Pacnet   .           Norway                       Datapak  .           Portugal                     Telepac  .           Singapore                    Telepac  /           South Korea                  Dacomnet1  .           Spain                        Iberpac  .           Sweden                       Datapak  ;           Switzerland                  Telepac (1978, 1980)n  -           Taiwan                       PacnetS  *           United Kingdom               PSS  .           United States                Accunet      +                                          11A e   J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3     1                                  Table 1: (Cont.)s2                          Supported Public Networks  G                                        Public Network          Comments F                                        and CCITT revi-         and Re-I           Country                      sion(s)                 strictions     .                                        Autonet  4                                        Bell Atlantic  1                                        Compuservec  .                                        ConnNet  -                                        IMPACSh  .           United States (cont.)        Infonet  8                                        Mark*Net Extended.                                        Service  .                                        Telenet  -                                        Tymnetu  :                                        Western Union PTN-1  /                                        Worldnet-  .           West Germany                 Datex-P             Note:t  I           1. Digital offices in Japan can supply the mandatory additional I              information that explains the special use of VAX P.S.I. witho              the DDX PSDN.    +                                          12  c  e    J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3       F              Unless otherwise acknowledged within the product documen-H              tation, the trademarks under which the services are offeredJ              are proprietary to the respective national PTT, the owning or=              operating companies, or equivalent organization.   "           Configuration Guidelines  H           Tables 2 and Table 3 describe the physical hardware configura-I           tions supported by VAX P.S.I. in terms of CPU type and communi-kJ           cation interface. It is assumed that there are 128 bytes of userI           data per packet in a VAX P.S.I. Native mode configuration whereaJ           data is being sent and received at maximum speeds in both direc-H           tions. These tables indicate configuration numbers for certain>           VAX processors supported at the time of publication.  H           The numbers given in the tables are load costs. Load costs in-I           dicate the overhead of full-duplex packet transfer at the indi-oG           cated speed. The load units are calculated for an applicationcH           that does no work with transmitted/received data, and indicateF           a maximum packet rate for that configuration. An idle deviceI           incurs negligible load. Systems should be configured to sustainr           peak load rates.                                  +                                          13a uJ           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3       J           ________________________________________________________________  -                                      Table 2: =                      CPUs, Maximum Load and Supported Devicesm  M                                                                     Supported M                                             Maximum load            Device(s) ;           CPU                               (in_load_units)a  J           MicroVAX 2000                     100                     DSH32,I                                                                     DST321  I           MicroVAX 3100                     350                     DSH32l  J           MicroVAX II                       160                     DSV11,J                                                                     DPV11-G                                                                     DA, J                                                                     KMV1A-F                                                                     A,I                                                                     DIV32a  J           MicroVAX 3300/3400                210                     DSV11,J                                                                     DPV11-F                                                                     S,I                                                                     DIV32a  J           MicroVAX 3500/3600/3602           330                     DSV11,J                                                                     DPV11-F                                                                     S,J                                                                     KMV1A-G                                                                     SF,eI                                                                     DIV32t                +                                          14n e  cJ           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3   2                                   Table 2: (Cont.)=                      CPUs, Maximum Load and Supported Devicest  M                                                                     SupportedhM                                             Maximum load            Device(s)g;           CPU                               (in_load_units)f  J           MicroVAX 3800/3900                390                     DSV11,J                                                                     DPV11-F                                                                     S,I                                                                     DIV32s    J           VAXstation II                     150                     DSV11,J                                                                     KMV1A-F                                                                     A,I                                                                     DIV32l  J           VAXstation 3200                   300                     DSV11,J                                                                     DPV11-F                                                                     S,J                                                                     KMV1A-G                                                                     SF,XI                                                                     DIV32   J           VAXstation 3500                   300                     DSV11,J                                                                     DPV11-G                                                                     DA,eJ                                                                     KMV1A-F                                                                     A,I                                                                     DIV32r                +                                          15k h  i  J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3     J           ________________________________________________________________  2                                   Table 2: (Cont.)=                      CPUs, Maximum Load and Supported Devices   M                                                                     Supported M                                             Maximum load            Device(s)n;           CPU                               (in_load_units)c    J           VAXstation 3520/3540              300                     DSV11,J                                                                     DPV11-G                                                                     DA, I                                                                     DIV32t    I           VAXserver 3100                    290                     DSH32e  J           VAXserver 3300/3400               210                     DSV11,J                                                                     DPV11-F                                                                     S,I                                                                     DIV32d  J           VAXserver 3500/3600/3602          280                     DSV11,J                                                                     DPV11-F                                                                     S,J                                                                     KMV1A-G                                                                     SF,sI                                                                     DIV32S  J           VAXserver 3800/3900               330                     DSV11,J                                                                     DPV11-F                                                                     S,I                                                                     DIV32l  J           VAXserver 6000-210                210                     DSB32,I                                                                     DMB32m          +                                          16a h  tJ           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3   2                                   Table 2: (Cont.)=                      CPUs, Maximum Load and Supported Devicesv  M                                                                     SupportedsM                                             Maximum load            Device(s).;           CPU                               (in_load_units)n    J           VAXserver 6000-310                250                     DSB32,I                                                                     DMB321  J           VAXserver 6000 Model 400          300                     DSB32,I           Series                                                    DMB32n    J           VAX-11/730                        40                      DUP11,J                                                                     DMF32,J                                                                     KMS1P-H                                                                     A/B,J                                                                     KMS11-E                                                                     Be  J           VAX-11/750                        70                      DUP11,J                                                                     DMF32,J                                                                     KMS1P-H                                                                     A/B,J                                                                     KMS11-E                                                                     Bn  J           VAX-11/780                        120                     DUP11,J                                                                     DMF32,J                                                                     KMS1P-H                                                                     A/B,J                                                                     KMS11-E                                                                     BA          +                                          17  t  s  J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3     J           ________________________________________________________________  2                                   Table 2: (Cont.)=                      CPUs, Maximum Load and Supported Devices   M                                                                     SupportediM                                             Maximum load            Device(s)r;           CPU                               (in_load_units)e    J           VAX-11/785                        180                     DUP11,J                                                                     DMF32,J                                                                     KMS1P-H                                                                     A/B,J                                                                     KMS11-E                                                                     B0  J           VAX 8600                          400                     DUP11,J                                                                     DMF32,J                                                                     KMS1P-H                                                                     A/B,J                                                                     KMS11-E                                                                     Bn  J           VAX 8650                          500                     DUP11,J                                                                     DMF32,J                                                                     KMS1P-H                                                                     A/B,J                                                                     KMS11-E                                                                     Bo    J           VAX 4000 Model 300                580                     DSV11,J                                                                     DPV11-F                                                                     S,I                                                                     DIV32             +                                          18r       J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3   2                                   Table 2: (Cont.)=                      CPUs, Maximum Load and Supported Devices   M                                                                     Supported M                                             Maximum load            Device(s)S;           CPU                               (in_load_units)e    J           VAX 6000 Model 200 Series         250                     DSB32,I                                                                     DMB32   J           VAX 6000 Model 300 Series         350                     DSB32,I                                                                     DMB32l  J           VAX 6000 Model 400 Series         450                     DSB32,I                                                                     DMB32     J           VAX 8200/8300                     100                     DSB32,I                                                                     DMB32   J           VAX 8250/8350                     125                     DSB32,I                                                                     DMB32   J           VAX 8500                          360                     DSB32,I                                                                     DMB32   J           VAX 8530                          450                     DSB32,I                                                                     DMB32   J           VAX 8550                          550                     DSB32,I                                                                     DMB32   J           VAX 8700                          700                     DSB32,I                                                                     DMB32T          +                                          19     sJ           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3     J           ________________________________________________________________  2                                   Table 2: (Cont.)=                      CPUs, Maximum Load and Supported Devices   M                                                                     Supported M                                             Maximum load            Device(s) ;           CPU                               (in_load_units)I    J           VAX 8800/8810/882/ 8830/8840      700                     DSB32,I                                                                     DMB32   J           VAX 8842                          700                     DSB32,I                                                                     DMB32   J           VAX 8978                          700                     DSB32,I                                                                     DMB32   J           ________________________________________________________________  @                                                         Table 3:N                                          Load Units per Line at Various Speeds  ]           Device Type        Number     Maximum              Load Units used at speed (K bps)                               of `                              Lines     Speed      4.8        9.6        19.2       48         64  b           DMB32              1          64.0       9          18         36         90         120  b           DSB32              2          64.0       9          18         36         90         120  -                              or 1       192.0   b           DMF32              1          19.2       9          18         36         N/S        N/S  b           DPV11-DA or        1          9.6        23         64         N/S        N/S        N/S
           -S*W  b           DST32              1          19.6       10         20         40         N/S        N/S    +                                          20o     J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3     B                                                   Table 3: (Cont.)L                                        Load Units per Line at Various Speeds  ]           Device Type        Number     Maximum              Load Units used at speed (K bps)                               ofe`                              Lines     Speed      4.8        9.6        19.2       48         64  b           DSH32              1          19.2       10         20         40         N/S        N/S  b           DUP11*             1          9.6        23         46         N/S        N/S        N/S  b           DSV11              2          64.0       9          18         36         90         120  -                              or 1       256.0a  b           DIV32**            2          64.0       N/S        N/S        N/S        N/S        120      b           KMS1P-A            1          19.2       9          18         36         N/S        N/S  b           KMS1P-B            1          64.0       9          18         36         90         120  b           KMS11-BD/BE***     8          19.2       10         20         40         N/S        N/S  b           KMV1A-A or -SF     1          19.2       9          18         36         N/S        N/S    I           *    For more than one character interrupt device, multiply theuJ                load units by 50% to allow for interaction between devices.  H           **   The DIV32 supports 2 B-channels at 64K bps per ISDN line.            +                                          21        J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3         I           ***  The KMS11-BD/BE are eight (8) line devices; the load units_I                indicated above are the load units for each active line at (                the indicated line speed.  J           N/S  The use of the device at this speed is not supported by VAX                P.S.I.                                                                 +                                          22        J           VAX Packetnet System Interface                    SSA 25.40.15-A            (P.S.I.), Version 4.3                  How to Use Table 3  G           The maximum system configuration, with a mix of device types, G           is computed by adding the load costs (in load units) for each <           device up to the limit for a given processor type.             Example 1:  I           A VAX 8500 is being used to process VAX P.S.I. Native mode com- H           munications. If the system uses a DMB32 at 64K bps and anotherF           DMB32 at 19.2K bps, the load units total 156. Assuming theseF           devices are fully active, they will consume 156/360 = 43% ofE           CPU for communications processing. It is inadvisable to add1I           more devices to this CPU, unless it is dedicated to the task of $           communications processing.             Example 2:  J           When one line of a DSV11 is fully utilized on a MicroVAX 3800 atI           64K bps, it consumes 120/390 = 31% of the processor in process- (           ing VAX P.S.I. communications.             Factors to Consider   I           Other factors to consider when configuring hardware devices for 7           use with VAX P.S.I. on a given processor are:   D           o  Multi-host mode increases the CPU load of packets to orF              from VAX P.S.I. Access systems due to the additional costE              of DECnet communications to the chosen VAX P.S.I. Access               node.  G           o  Hardware configuration limits, such as power supply, back-eI              plane space, bus throughput and mapping registers available, H              and any other restrictions on the number of devices per CPU*              or per bus, must be observed.  J           o  Actual/average Packet size in bytes - generally, doubling theJ              actual packet size will halve the load units consumed for DMAI              devices, but increase the load units for character-interrupt 1              devices by approximately 30 percent.   +                                          23            F           o  The above table assumes that data is sent and received inH              each direction of a full-duplex line in equal ratio. If theH              number of X.25 packets per second is predominantly one-way,I              the load units per line can be reduced proportionately up to               a factor of 50%.1  ?           [TM] Bell is a trademark of Bell Telephone Companies.   D           [R]  The DIGITAL Logo is a registered trademark of Digital%                Equipment Corporation.   F           [TM] DECnet-VAX, VAX, MicroVAX, VAXstation and VAXserver are;                trademarks of Digital Equipment Corporation.                                                     +                                          24 