31 Jul
2004
31 Jul
'04
6:17 a.m.
From: "Joe R." <rigdonj(a)cfl.rr.com>
OK, that helps a lot to get me on the same page.
Can you use the 74S571? Those appear to still be available from JameCo
(part #48910) at 35ns address-to-data, 25ns enable-to-data. They are 512x4
16 pin DIPs. $5.69 qty 1, $5.49 qty 10. Haven't found them elsewhere,
though.
Not knowing what I am looking for, I wasn't able to find the pinouts on Al's
site, however. Can you provide a pointer or at least a part number?
For one thing the parts used in the HP 1000 are 25
to 35 nS parts. Also
the enable and other control lines are very different so you'd need a fair
amount of glue chips and probably a buffer.
>(I don't know the specs for the bipolar ROMs
being replaced. Someone
>earlier said they were 50-60ns. I am assuming they were also fairly
small
(logically, if
not physically) compared to a 27c256.)
The ones in the HP 1000 are 4 x 256 and are sixteen or eighteen (I
forget which) pin .3" wide DIPs. Al has pins out for some of the different
BiPolar PROMs on his site. I think they're under the games machines
section. There's no room for a duaghterboard to mount on
the HP 1000 card.
You'd have to mount it elsewhere and cable over to it.
Wouldn't that cost you a few nanoseconds just in the cabling? ISTR cable
delays measured in ns/ft.
Thanks!
Vince