PDP-11/03, LSI-11 KEV11-C CIS option

John Wilson wilson at dbit.com
Sun Jan 31 23:24:43 CST 2016

On Sun, Jan 31, 2016 at 03:52:57PM -0700, Eric Smith wrote:
>I think the KEV11-C is not full CIS, but rather a subset. It's usually
>described as DIBOL Instruction Set (DIS).

OK the DIS part is hazily familiar, but still, neat!

>> I have the QIL CIS micROM for the LSI-11/23, and I too have been meaning
>> to build a ROM dumper for it, since it's a rare part but could be easily
>> emulated with modern hardware on a daughterboard (easier than the 11/44
>> anyway, where the CIS option means extra boards).
>I've got bad news for you. The control chips of the F11 chipset aren't
>just ROMs; they include the control sequencer (one per control chip).
>Unless there's an undocumented test mode, it's not possible to dump
>the full microcode word, since only part of it is output to pins, and
>it's not possible to dump the contents purely sequentially.

That IS bad news!  I'd grasped that there was a little more going on in
there than just ROM, but I didn't realize it was that much more.

>On the other hand, as you say, if we could dump the KEF11-B CIS
>control chips (optically or otherwise), we could build a replacement
>daughtercard that emulates KEF11-B, and then anyone that wanted to
>have CIS on their 11/23 or 11/24 would have a relatively low-cost
>option to do so.

Yeah that would be pretty slick.  The only real problem with CIS was
that it was too rare to use, for the most part anyway.

>I'd really like to get the F11 base instruction set control (part of
>the DCF11 hybrid) and the KEF11-B CIS (six chip hybrid spanning two
>40-pin DIP sockets) to be dumped in this way, but only if someone is
>willing to sacrifice them. Given that the KEF11-B is fairly uncommon,
>I'm not holding my breath...

I'd certainly want to see something mostly just like it successfully
read, before offering mine up to be next in line.  But, the beauty of
computers is doing useful work, not hanging on the wall and being
pretty ... so I feel like the "museum piece" mindset can easily be
taken too far.

John Wilson
D Bit

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