MA780 Multiport Memory Option
The MA780 Multiport Memory Option was a MOS DRAM multi-port memory main memory system for the VAX-11/780; it allowed creation of multi-processor systems such as the VAX-11/782. It was 64 bits wide, to interface to the -11/780's Synchronous Backplane Interconnect (SBI), and provided ECC (8 bits/double-word), which could correct all single-bit errors.
An MA780 system was comprised of:
- the main MA780 unit, which contained a custom backplane holding i) a small group of control cards, and ii) a variable number of array cards (between 1 and 8 per MA780), holding the DRAM chips; and
- in each connected CPU (between 2 and 4), an MA780-C Port Interface, held in another, smaller custom backplane, which connected the main MA780 unit (up to two different ones per MA780-C) to the host CPU's SBI.
With the 256-Kbyte M8210 array card (shared with the MS780-C), this allowed a maximum of 2MB per MA780. The -11/780 thus supported up to 2 MA780 subsystems, for a maximum of 4MB with fully populated MA780's.
Implementation
The main MA780 was implemented on super hex cards, mounted in a custom 20-slot backplane. The cards were:
| Slot | Board | Acronym | Function |
|---|---|---|---|
| 1 | M8210 | MAY | Memory Array (optional) |
| ... | |||
| 8 | M8210 | MAP | Memory Array |
| 9 | M8210 | MAP | Selective Map Cache (optional) |
| 10 | M8261 | MPS | Multiport Port Synchronizer |
| 11 | M8212 | MDT | Memory Data Paths |
| 12 | M8260 | MAT | Multiport Array Timing |
| 13 | M8259 | MPC | Multiport Port Control (Port 3 - optional) |
| 14 | M9045 | BDI Connect (rear) | |
| 15 | M8259 | MPC | Multiport Port Control (Port 2 - optional) |
| 16 | M9045 | BDI Connect (rear) | |
| 17 | M8259 | MPC | Multiport Port Control (Port 1) |
| 18 | M9045 | BDI Connect (rear) | |
| 19 | M8259 | MPC | Multiport Port Control (Port 0) |
| 20 | M9045 | BDI Connect (rear) | |
Slots 1-8 held 256-Kbyte M8210 array cards; a minimum of one, in slot 8, was required.
The MA780-C was mounted in a custom 20-slot backplane. The contents were:
| Slot | Board | Acronym | Function |
|---|---|---|---|
| 1 | Blank | ||
| 2 | M9040/M8258 | SBI Terminator / Multiport Port Interface (optional) | |
| 3 | M8258 | Multiport Port Interface | |
| 4 | M9045 | BDI Connect (rear) |
External links
- VAX Maintenance Handbook VAX-11/780 1983 Edition (EK-VAXV2-HB-002) - the MA780 is covered on pp. 235-253
- VAX-11/780 Installation Manual (EK-SI780-IN-002) - the MA780 is covered in Chapter 9 (on pp. 71-122 of the PDF)
