BM873 ROM
The BM873 ROM card was a UNIBUS card for the PDP-11 series of computers; it was a quad format card, and contained 256 words of memory (optionally limited to 128 words).
The board appeared at addresses from 773000 to 773776; if the 128-word limitation is enabled, the top address is 773376. Several of the computers it was intended for use with (PDP-11/40, PDP-11/45) could be configured so that the host computer jumped to the code on the board on power-on.
In addition, an edge connector provided four wires, each of when (when puilled low) forced the computer to jump to a particular address (configured by a group of 8 diodes, four groups in total) within the card's address space.
Most versions were used for bootstrapping the machine, from disk, paper and magnetic tape, etc, but it could be use for any purpose
The board came in several main variants, designated BM792-Yx (where 'x' is a capital letter, starting with 'A'); they all came pre-programmed from DEC to perform various functions. Many of the later variants were used to boot the PDP-11/40 used as the front-end processor in the KL10.
Variants
- BM873-YA - Boot from disks (RF11, RK11, RP11, RC11), TC11 DECtape, TM11 magnetic tape, TA11 casette magnetic tape, serial line, and high-speed paper tape reader
- BM873-YB - As above, with the addition of RS0x and RP0x disks and TU16 tapes; in addition, booting from units other than 0 (with the unit being specified in the console switch register)
- BM873-YC - As the -YA variant, with added support for the DU11 synchronous line interface
- BM873-YD - 1080 console, supported booting from TC11, RP0x, and DTE20 10/11 interface
- BM873-YE - Unknown
- BM873-YF - 2040 console
- BM873-YG - DN87 communications
- BM873-YH - 10xx/20xx console
- BM873-YJ - 10xx/20xx console/communications
See also
Reference
- EK-BM873-TM-004, BM873 restart/loader
- KL873.MEM, KL10 BM873 Bootstrap ROMs
