a classiccmp electronics project?

From: Dwight K. Elvey <dwight.elvey_at_amd.com>
Date: Thu Jul 29 19:02:30 2004

Hi Jay
 Al and another fellow at Monday pizza talked about this.
One could setup using one of the high speed CMOS cache
chips, pic ( or processor of your liking ) and an EPROM.
One can hold the reset signal until you'd transfered the
image to the CMOS ( it would have space for just about
every combination ). One could even use a flash instead
of an EPROM and then add a serial port to download.
 Most of the fused ROM's used in the original were in
the 50 to 60 ns range. Most 8Kx8 cache RAM's are in the
20 to 30 ns range.
 It sure sounds like a project that can be done.
Dwight

>From: "Jay West" <jwest_at_classiccmp.org>
>
>Ok, I don't know if this is possible, but it would be handy so I'll throw
>the idea out and see if the more electrically inclined have any ideas.
>
>My specific issue is the HP2100A, 2100S, and 21MX M/E/F systems. However, I
>suspect this problem is present in other machines... DEC, DG, etc.
>
>The loader roms and microcode roms (two different chips) for each system are
>pretty much impossible to find. I'd like to make copies of them both for
>myself to use in other systems I currently have, and also to have a set of
>spares around. In addition, I'd like to make copies for other classiccmp'ers
>who may have systems that want/need a particular firmware or loader rom
>option. Finally, there are some roms that people have posted images for
>online that I'd like to burn myself because I don't have those particular
>roms.
>
>Since the blank chips are nigh impossible to find anymore... is it possible
>to use something like a PIC chip on a small DIP carrier card, that could be
>plugged into an existing loader rom or microcode rom socket and function
>just like the "real thing" to the system? Would this be something terribly
>difficult to build? A cute twist on this.... extending the idea further....
>Put a bunch of NVram or an EEprom on the little carrier card. In the NVram
>could be stored multiple ROM images. Then via a switch on the card (when the
>system is powered off of course), you could select if the chip was a mag
>tape loader rom, or a paper tape loader rom, etc. For the microcode roms you
>could switch between FFP and IOP for example. When you wanted to change the
>set of rom images in the DIP package, you just hook it up to a serial port
>and download to change the available sets on it.
>
>The WCS card for HP boxes comes close to this, but there's no battery
>backup, and you can't program it easily with a PC. WCS cards probably aren't
>terribly easy to find anyways.
>
>Is this a pipedream? It would allow DEC'ies to have more loader roms they
>dont currently have by exchanging images via the net, etc. Not just an HP
>thing - but I realize it would have to be a different design electrically to
>work on the other machines. I'm thinking of a universal rom with different
>electrical interfaces on the carriers perhaps?
>
>Everyone talks about preserving ROM/PROM contents. But if the blank roms are
>unobtainium, we need to take the next step.
>
>Any thoughts?
>
>Jay West
>
>---
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Received on Thu Jul 29 2004 - 19:02:30 BST