UNIBUS M9312 ROMS

On 6/8/2016 3:13 PM, Mike Ross wrote: I have tried to compress/adapt the TMSCP boot in the PDP11 SIMH device driver, a bootstrap listing in a DEC tech manual, and using the programming concepts (hacks) in the MSCP DU M9312 boot prom 23-767A9, and have not been able to get a valid code image that fits in the PROM and has all the required functionality. So DEC must have taken some magic shortcut to get working TU boot code in the 23-E39A9 PROM. As to programming parts, I use an EETools TopMax programmer that I have had for years. It will do just about any of the older programmable devices. There are other programmers around (old DataIO's for example) that can do these bipolar PROMs. Also, M9312 boot PROMs are typically 82S131 (or equiv) 512x4 tristate devices, but only half the device is used; the other half of the device is never accessed on the M9312 and is just blank filled. An 82S129 (or equiv) 256x4 tristate device works just as well as a boot PROM as the upper address pin becomes an active low chip select, and this pin is pulled low on the M9312 board. -- Don North AK6DN