Don North ak6dn at mindspring.com
Wed Jun 8 17:37:00 CDT 2016

On 6/8/2016 3:13 PM, Mike Ross wrote:
> On Thu, Jun 9, 2016 at 6:34 AM, Jay West <jwest at classiccmp.org> wrote:
>> 23-E39A9 is still lost to time, afaik. TMSCP - TU81
> Could that not be reverse-engineered from the boot code in e.g. Emulex
> UC17 ROMs? They could do TMSCP...
> BTW what PROM blower would folks recommend for creating/imaging M9312 ROMs?
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

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