M9301 ROM

The M9301 ROM card was a UNIBUS card for the PDP-11 series of computers; it was a dual format card, and contained 512 words of memory, all readable direction from the UNIBUS (i.e. not windowed).

Most versions were used for bootstrapping the machine, from disk, paper and magnetic tape, etc, but it could be use for any purpose; most versions included a console emulator, and basic diagnostics.

It used four 4-bit wide PROMs to hold the data. The board occupied addresses 773000-773776 and 765000-765776; a configuration switch allowed the lower block to be disabled.

Other configuration switches controlled which address the CPU jumped to on power on; a clever kludge, controlled by one configuration switch, allowed the board to force the CPU to read its power-on PC and PS from the ROM, at a location set by other configuration switches, thereby allowing auto-boot on power-on.

The M9301 also provided termination for the UNIBUS. There were two different etch revisions of the card itself, but they seem to be programming-wise identical.

The board came in several main variants, designated M9301-Yx (where 'x' is a capital letter, starting with 'A') came pre-programmed from DEC to perform various functions.

Variants

• M9301-YA - PDP-11/04 and PDP-11/34 OEM version; had basic diagnostics, console emulator, booted from various devices (RK11 and RP11 disks, TC11 DECtape, TM11 magnetic tape, serial line, high-speed paper-tape reader, TA11 casette tape, RX11 8-inch floppy), supported auto-boot on power on, and also power-fail restart

• M9301-YB - /04 and /34 end user version; had basic diagnostics, console emulator, booted from various devices (RK11, RP11, TC11, TM11, TA11, RX11, serial line, high-speed paper-tape reader, RJS, RJP, TJU), also power-fail restart

• M9301-YC - PDP-11/70 version; contained basic CPU, cache and memory diagnostics, booted from various devices (TM11, TC11, RK11, RP11, RK06, RJS, RJP, TJU, RX11)

• M9301-YD - All models; contained code to allow a terminal attached to the machine to be a terminal on some other line; also had boot code for RX11 and DDCMP

• M9301-YE - All models; had basic diagnostics, console emulator; booted from low speed paper tape or DECnet; supported auto-boot on power on, and also power-fail restart

• M9301-YF - All models (auto-start not available on PDP-11/45, PDP-11/50); had basic diagnostics, console emulator, booted from various devices (RK11, RK06, RP11, TC11, TM11, TA11, RX11, serial line, high-speed paper-tape reader, RJS, RJP, TJU), supported auto-boot on power on, and also power-fail restart

• M9301-YH - /60 and /70 version; contained basic CPU, cache and memory diagnostics, booted from various devices (TM11, TC11, RK11, RP11, RK06, RJS, RJP, TJU, RX11, high-speed paper-tape reader)

• M9301-YH - All models; had basic diagnostics, console emulator; booted from DECnet, and various devices (RX11, TU, serial line, DMC), also power-fail restart

Reference

• EK-M9301-TM-001, M9301 bootstrap/terminator module