UNIBUS M9312 ROM type identification

JP Hindin jplist2008 at kiwigeek.com
Wed Sep 7 10:57:03 CDT 2016

On Tue, 6 Sep 2016, Don North wrote:
> On 9/6/2016 9:23 AM, JP Hindin wrote:
>> Greetings;
>> My googlefu is failing me and I was wondering if someone might be able to 
>> help me identify one of the boot ROMs present in an M9312 bootstrap/term 
>> board. The board has three ROMs, an RX01 (042130), an RX02 (042131) and 
>> then a mystery code - 043127.
>> The M9312 ROM identification table does not list this ROM code - I suspect 
>> it _might_ be for a DSD combined 8" drive and Winchester disk box, but I'm 
>> under the impression this would appear as a DU device, and attempting to 
>> boot from DU gets an ILL CMD, suggesting otherwise. I tried all of the 
>> other possible mnemonics listed in the M9312 manual, so it doesn't appear 
>> to piggy-backing on any of those either.
>> My thanks;
>>  - JP
> Octal word 042130 decodes as ascii "DX", which is the M9312 boot mnemonic for 
> the RX01 drive/RX11 controller combo.
> Octal word 042131 decodes as ascii "DY", which is the M9312 boot mnemonic for 
> the RX02 drive/RX211 controller combo.
> Octal word 043127 decodes as ascii "FW", which is not a standard M9312 boot 
> mnemonic. Probably a third party manufacturer custom boot prom.
> FYI the above octal words are programmed in the first word of each boot PROM, 
> so they are accessible at locations 773000,
> You can find program listings and hex PROM images of all the known M9312 
> devices here:  http://www.ak6dn.com/PDP-11/M9312/, including the DX and DY 
> PROMs.

It didn't even occur to me that this was octal encoded ASCII, this is 
great, thank you. As Al suggests, it is going to an SMS device, so it 
looks like we've got a winner.

I managed to get an RX01 (although it's an RX02 box, took me a while to 
figure that one out) hooked up with what are supposed to be bootable 
disks,  but I get a Boot Error each time - so I think I have something 
probably off in the hardware, but in _theory_ the SMS is supposed to have 
a bootable OS image on its Winchester from the 1990s, so that might be 

Thanks all!

  - JP

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