VAX-11/780

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VAX-11/780
Summary
Announcement date: October 1977
Codename: Star
OS support (VMS): VMS V1.5
CPU Details
CPU name (VMS): KA780
Number of processors: 1
CPU technology: Bipolar Schottky
CPU cycle time: 200ns [1]
Instruction-buffer: 8 bytes [1]
Translation-buffer: 128 entries [1]
Control store: 4K 99-bit words [1]
Gate delay: 3ns
User Writable Control Store: 2K 99-bit words [1]
Cache: 8KB [1]
Compatibility mode: Yes [1]
Console processor: LSI-11 [1]
Console device: RX01 [1]
Memory
Minimum memory: 2MB
Maximum memory: 64MB
Physical address lines: 30
Memory checking: 8-bit ECC/longword [1]
I/O
Max I/O throughput: 5.0MB/s
MASSBUS: 4 @ 2.0MB/s
UNIBUS: 4 @ 1.5MB/s
LAN support: optional
Performance
VUPs: 1.0 [2]


A 'typical' VAX-11/780 marketing image

The VAX-11/780 was the first member to ship of the VAX family of larger computers. The VAX series was conceived as the successor to the successful PDP-11 series of minicomputers; in order to make the VAX seem more PDP-11 friendly, they retained the -11 moniker for the first VAXen, and provided the ability to execute PDP-11 object code - hence the -11/780 designation.

One of the main design goals was to increase the address space available, in fact the 'VAX' acronym originally stood for Virtual Address eXtension).[3] The first VAX-11/780 systems shipped with one quarter of a megabyte of main memory, built from 4Kb chips.[3]

The 11/780 didn't have just firmware; instead it loaded microcode from secondary storage (a floppy disk), under the control of a front end (a PDP-11/03).

It was announced on October 25th, 1977 at DEC's Annual Meeting of Shareholders.[4] The VAX-11/780 was given the codename "Star" and its operating system, VAX/VMS, was codenamed "Starlet".[4] VAX/VMS Version V1.0 shipped in 1978, along with the first revenue-ship 11/780s.

There was also the VAX-11/785, which was an upgraded version.

Subsystems

The CPU, the KA780, could take an optional floating point accelerator, the FP780 Floating-Point Accelerator; the floating point instructions were performed by the microcode when it was not installed.

The CPU and the other major subsystems in the VAX-11/780 - the MS780 Memory System main memory, and the RH780 Massbus Adapter and DW780 Unibus Adaptor I/O bus adapters - were connected via a new bus, the Synchronous Backplane Interconnect (SBI).

Implementation

The CPU was implemented with a large group of hex cards:

Slot Board Acronym Function
29 M8236 CIB Console Interface Board
23 M8235 USC Microsequencer
22 M8234 PCS PROM Control Store
20 M8233 or M8238 WCS Writeable Control Store
18 M8233 or M8238 OCS Optional Control Store
16 M8232 CLK Processor Clock
15 M8231 ICL Interrupt Control
14 M8230 CEH Condition Codes/Exceptions
13 M8229 DAP Data Path
12 M8228 DCP Data Path
11 M8227 DDP Data Path
10 M8226 DEP Data Path
9 M8225 DBP Data Path
8 M8224 IRC Instruction Decode
7 M8223 IDP Instruction Buffer
6 M8222 TBM Translation Buffer
5 M8221 COM Cache Data
4 M8220 CAM Cache Address
3 M8219 SBH SBI High Bits Interface
2 M8218 SBL SBI Low Bits Interface
1 M8237 TRS SBI Terminator and Silo

Dual-CPU experiment

"In 1981, [George H. Goble] wired together the backplanes of two DEC VAX-11/780's and made the first multi-CPU Unix computer, preceding DEC's dual processor VAX-11/782. The operating system was based on the 4.2 BSD kernel, and the modifications thus made eventually made it into the 4.3 BSD Unix release. At the beginning of the 4.3 BSD user manuals, Bill Joy wrote a special note of thanks to GHG for being courageous enough to put the multi-CPU kernel into a production environment before anyone else did. (However, the frequent crashes for a while inspired the writing of many humorous text files by the Purdue University Electrical Engineering student body, such as 'The VAX had a Blowout', to be sung to the tune of London Bridge is Falling Down). The development of the Dual-CPU Unix system was the subject of Goble's Master's thesis."

Operating Systems

An actual VAX-11/780 system

The 11/780 was to ship with VMS 1.0.

Emulation

SIMH is the only known emulator for the 11/780. SIMH can address up to 128MB of RAM emulating an 11/780. Also the following peripherals are emulated:

  • CPU VAX-11/780 CPU
  • TLB translation buffer
  • SBI system bus controller
  • MCTL0,MTCL1 memory controllers, MS780C with 4MB memory each, or MS780E with 8MB-64MB each
  • UBA DW780 Unibus adapter
  • MBA0,MBA1 RH780 Massbus adapters
  • TODR time-of-day clock
  • TMR interval timer
  • TTI,TTO console terminal
  • RX console RX01 floppy disk
  • DZ DZ11 8-line terminal multiplexer (up to 4)
  • CR CR11 card reader
  • LPT LP11 line printer
  • RP RP04/05/06/07, RM02/03/05/80 Massbus disks, up to eight drives
  • HK RK611/RK06(7) cartridge disk controller with eight drives
  • RL RL11/RL01(2) cartridge disk controller with four drives
  • RQ UDA50 MSCP controller with four drives
  • RQB second UDA50 MSCP controller with four drives
  • RQC third UDA50 MSCP controller with four drives
  • RQD fourth UDA50 MSCP controller with four drives
  • RY RX211 floppy disk controller with two drives
  • TS TS11 magnetic tape controller with one drive
  • TQ TUK50 TMSCP magnetic tape controller with four drives
  • TU TM03 tape formatter with eight TE16/TU45/TU77 drives
  • XU DEUNA/DELUA Ethernet controller
  • XUB second DEUNA/DELUA Ethernet controller

More information about SIMH's VAX 11/780 emulation can be found here.

Related Documents

VAX 11/780 Architecture Handbook Vol. 1 1977-78. EB-07466-20
VAX-11/780 Hardware User's Guide. EK-11780-UG-001
VAX-11/780 Installation Manual. EK-SI780-IN-002
VAX 11/780 Hardware Handbook 1979-80. EB-17835-18
VAX Maintenance Handbook VAX-11/780. EK-VAXV2-HB-002
VAX-11/780 Diagnostic System Technical Description. EK-DS780-TD-001
VAX-11/780 Diagnostic System User's Guide. EK-DS780-UG.002
MS780-E MS780-H Memory Subsystem Technical Description. EP-780EH-TD-002
KA780 Central Processor Technical Description. EK-KA780-TD.001
Translation Buffer, Cache and SBI Control Technical Description (VAX-11/780 Implementation). EK-MM780-TD-001
MS780 Memory System Technical Description. EK-MS780-TD-001
FP780 Floating-Point Accelerator. EK-FP780-TD.001
KC780 Console Interface Board Technical Description. EP-KC780-TD-001
KC780 Family Remote Diagnosis Options Technical Manual. KC780, KC782 and KC785. EK-KC780-TM-007
VAX/11/780 Microprogramming Tools User's Guide. AA-H306B-TE
VAX-11/780 Data Path Description. AA-H307B-TE
VAX-11/780 Sofwtare Installation Guide. AA-M545B-TE
CI750 CI780 Computer Interconnects Maintenance Advisory. EP-CIVAX-RM-001
VAX-11/780 Unibus Adapter Technical Description. EK-DW780-TD.001
RH780 Massbus Adapter Technical Description. EK-RH780-TD-001
Guide to VAX-11/780 System Troubleshooting. EY-2217E-SG-0001
KA780 Field Maintenance Print Set. MP00496
DW780 Field Maintenance Print Set. MP00497
KC780 Field Maintenance Print Set. MP00534
11780 Field Maintenance Print Set. MP00539
MS780-H Field Maintenance Print Set. MP01759

References

[1] VAX Hardware Handbook Volume 1 - 1986.
[2] Systems & Options Catalog. European Edition. Spring 1990.
[3] VAX Architecture Reference Manual. Timothy E. Leonard. 1987. EY-3459E-DP. ISBN 0-932376-86-X.
[4] Nothing Stops It! VAX Open VMS At 20.

External links