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Announcement date: April 1982
Codename: Nebula
OS support (VMS): VMS V3.0
CPU Details
CPU module: KA730
Number of processors: 1
CPU technology: Bipolar Schottky
CPU cycle time: 270ns [1]
Instruction-buffer: 4 bytes [1]
Translation-buffer: 128 entries [1]
Writable Control Store: 16K 24-bit words [1]
Compatibility mode: Yes [1]
Console processor: 8085A [1]
Console device: TU58
Minimum memory: 1MB [1]
Maximum memory: 5MB
Physical address lines: 24 [1]
Memory checking: 7-bit ECC/longword [1]
Memory cycle: 810ns [1]
UNIBUS: 1 @ 1.5MB/s [1]
LAN support: optional
VUPs: 0.3

The VAX-11/730 was the third VAX introduced, and the slowest implementation of the VAX architecture to have been made. By way of extensive microcoding of the large architecture, the CPU was shrunk to three hex boards. The machine seems to have been most popular for application development projects for the VAX - where the architecture was needed, but not necessarily performance.

It was also sold as VAX-11/725, which was a smaller-size packaging of the same machine.

It uses the UNIBUS for one of its input/output buses; the 'Port Bus', used for data transfer, is the other. The only device on the Port Bus is the RB730 Integrated Disk Controller, which also connects to the UNIBUS for interrupts (it plugs into a dedicated, custom backplane slot). The main memory uses the same internal memory bus as the MS750 Memory System (and thus the same memory array modules, 1-5 of them).

A DMF32 Multi-Function Communications Interface is usually included, to provide a variety of low-speed I/O capabilities.

The front panel functionality is performed by an 8085A microprocessor, which uses a TU58 magnetic tape drive for mass storage. The 8085A and associated circuitry (three asynchronous serial lines; for the console, TU58, and a modem for remote diagnosis) are contained on the Writeable Control Store CPU card.

Hardware Details

The boards are all mounted in a BA11-Z mounting Box, which holds a custom 12-slot backplane (DEC part number 70-18080-0-1 for the complete assembly). In addition to the slots for the CPU, main memory, and IDC, it provides a slot which can be used to hold the DMF32 (probably a MUD/SPC slot, but this is not confirmed), and one SPC slot, which also contained the 'UNIBUS out'.

Board locations are:

Slot A B C D E F
1 RB730 IDC (M8388)
2 FP730 FPA (M8389)
3 KA730 DAP (M8390)
4 KA730 MCT (M8391)
5 KA730 WCS (M8394)
6 MS730-CA Memory 0 (M8750)
7 MS730-CA Memory 1 (M8750)
8 MS730-CA Memory 2 (M8750)
9 MS730-CA Memory 3 (M8750)
10 MS730-CA Memory 4 (M8750)
11 DMF32-AA (M8396)

Apparently the bus grant lines are run through the memory slots (perhaps so that they can be used to hold peripherals if they are otherwise unused, but this has not yet been documented); a G7273 grant continuity card must be installed in any unused memory slot.

The 'UNIBUS out' slot will hold an M9302 UNIBUS terminator if there is no expansion box to hold other peripherals.

See also


[1] VAX Hardware Handbook Volume 1 - 1986.
[2] Systems & Options Catalog. European Edition. Spring 1990.

External links