VAX-11/750

VAX-11/750
VAX-11/750
Codename:	Comet
Year Introduced:	October 1980
RAM:	Max of 14 MB
VUPS:	0.65

The VAX-11/750 (also known as the VAX/750) is a slower, more compact, but less expensive version of the VAX-11/780. It was built around the CPU/Memory Interconnect bus (CMI); the mandatory major CMI sub-systems (and components thereof) were:

• KA750 CPU
  • UI750 UNIBUS Interface
  • FP750 Floating-Point Accelerator (optional)
• MS750 Memory System

It was codenamed 'Comet' by DEC. One of the first OS's available for the 750 was 4.1 BSD. According to 'Quarter Century of UNIX', the DoD could purchase 6 750's for about $150,000 USD.

CMI Options

The CMI was instantiated as a large backplane; option slots in the backplane can be used for a variety of optional adapters:

• RH750 Massbus Adapter - L0007
• CI750 Computer Interconnect Interface (CI)
• DW750 Second Unibus Interface
• DR750 Parallel Interface

Allowable Configurations of CMI Slots 7, 8, & 9 are:

Slot 7	Slot 8	Slot 9
RH750	RH750	RH750
DW750	RH750	RH750
DR750	RH750	RH750
DW750	DR750	RH750
DW750	CI750	RH750
CI750	RH750	RH750

NOTES:

1. Combination of DR750 and CI750 is not allowed
2. Only one DR750 per system is allowed
3. Only one DW750 per system is allowed
4. Only one CI750 per system is allowed

CMI backplane configuration

Slot	Contents
1	L0001 Floating-Point Accelerator (FPA)
2	L0002 Data Path Module (DPM)
3	L0003 Memory Interconnect (MIC)
4	L0004 UNIBUS Interface (UBI)
5	L0005 CPU Control Store (CCS)
6	L0006 Remote Diagnostic Module (RDM)
7	CMI Option
8	CMI Option
9	CMI Option
10	L0011/L0016/L0022 Memory Controller (MCM)

VAX-11/750 images

View into a VAX-11/750 card cage

Left of card cage:

• Top: 54-13489 - TU58 controller
• Bottom: H7112 - VAX-11/780 / VAX-11/750 Battery Backup Unit

Inside card cage:

• Left: DD11-DK Unibus Backplane (with cards)
• Center: Memory Backplane (with cards)
• Right: CMI Backplane (with cards)

View of VAX-11/750 backplanes from behind

Backplanes:

• Left: CMI Backplane
• Center: Memory Backplane
• Right: DD11-DK - Unibus Backplane
• Lower left corner: 5V and 2.5V Power Supply cables (as thick as a finger!)
• Bottom: 5V and 2.5V Power Supplies

VAX-11/750 Power Supply Units

Power Supplies:

• Left: H7104-C 2.5V, 85A max.
• Right: H7104-D 5V, 135A max.

Cable Routing inside VAX-11/750 (left side open)

Round cables top left:

• Console
• Remote Diagnose Modem

Cables bottom left to top right:

• DMF32 Unibus Combo Module (3 flat cables)
• TU80K TU80 Tape Adapter (2 flat cables, one behind the other)
• DEUNA Ethernet Adapter (round cable)

Bottom right:

• H7112 - VAX-11/780 / VAX-11/750 Battery Backup Unit

See also

• VAX-11/750 & VAX-11/751 Revision Control
• VAX-11/751

External links

• VAX Hardware Handbook Volume 1 - the VAX-11/750 is covered in Chapter 4 (pp. 154-171 of the PDF)
• VAX Maintenance Handbook: VAX-11/750 (EK-VAXV3-HB-001)
• VAX/750 - documentation at Bitsavers
  • 11/750 Field Maintenance Print Set (MP01377)
• Vax 11/750 Frequently Asked Questions
• VAX-11/750
• Makings of a Comet: The VAX 11/750