Memory/cache on the 11/70
mcguire at neurotica.com
Fri Jan 9 18:33:58 CST 2009
On Jan 9, 2009, at 5:59 PM, Ethan Dicks wrote:
>>>> Standard chips good. Weird chips from the PC world, bad.
>>> I'm not advocating the reuse of SMT 128K cache chips, but the 32Kx8
>>> DIP chips from old motherboards have a JEDEC-compatible pinout...
>> Hence, they're not "weird chips". =) It's the weird ones I'm
> OK. I think we are on the same side here ;-)
We usually are. :)
>>> The DIP cache SRAMs are no longer cheap-as-chips, but some of us
>>> a tube or two stashed away and I sure don't mind using them for
>>> non-battery-powered circuits.
>> The JEDEC ones, or the "weird" ones?
> JEDEC ones - I don't have the time to untangle wierd ones.
Yeah. The weird SRAMs that the SBC6120 uses are PC cache chips
too, aren't they? They've become pretty tough to find in recent
years. I really like that they're four bits wide, though, for that
>> I see some from time to time, and I
>> grab them if they're "standard" enough. I got a pair of really
>> 20ns nice
>> cache SRAMs on eBay last year, Paradigm PDM41256SAs. Despite their
>> seemingly familiar part number, they are 32kx8 SRAMs, not 256kx1
>> They're in 0.3" ceramic 24-pin DIPs. I'm saving them for a
>> "pretty" Z80
>> SBC that I'll be building soon, on which all chips are ceramic.
>> always had a great love for ceramic chip packages, and I grab useful
>> ceramic-packed chips whenever I can)
> Nice. Sounds like it'll have great presentation value.
Thanks, I think so too. And it'll weigh a few pounds! :)
> You have purple ceramic for the VLSI or just grey?
I've got the Z80 CPU, CTC, SIO, and PIO chips in purple/gold.
I've got some purple/gold SRAMs, but not quite enough for this
project. Chuck has some medium-density purple/gold 16Kbx1 SRAMs that
I'm thinking about trying to talk him out of. If I don't go that
route, I'll probably use those Paradigm gray ceramic SRAMs. I'll do
the address decoding and other sundry stuff in a ceramic UV-erasable
PAL22V10, of which I have a few tubes.
I also have some HP intelligent hex displays, along the lines of
the TIL-311, I'm sure you've seen them. Most of them are
encapsulated in red injection-molded plastic, but I have a handful of
fairly rare 5082-7359s, which are hermetically-sealed purple ceramic
with a glass cover. They are absolutely gorgeous.
I'll probably put the board between two 0.25" pieces of lucite.
Port Charlotte, FL
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