a classiccmp electronics project?

From: Joe R. <rigdonj_at_cfl.rr.com>
Date: Sat Jul 31 09:06:38 2004

At 06:21 PM 7/30/04 -0700, you wrote:
>> >I must not be getting it, somehow.
>> >
>> >Why can't you just use a 45ns or 55ns 27c256 or 27c512 and swizzle the
>> >pinout? These are around $3 per chip, and seem to meet the requirements.
>> >
>> > Vince
>>
>> Hi
>> I did some searching on the web but never found any
>> 27c256's faster than 70ns. I did find 27c512's and 27c010's
>> at 45ns a couple of places.
>> Dwight
>
>(Looks again.) I found 27c256 and 27512 at 45ns at Digikey, and 45ns 27c512
>at JameCo. Mouser also has the 45ns 27c256, but only has 55ns 27c512. (Are
>you in the states?)
>
>So, do these meet the requirements? (Seems like you could even burn several
>different images into the chips and use a DIP switch to select which image
>using the high address lines :-).)
>
>Also needn't worry about holding reset, or batteries going dead, or a big,
>complicated daughter board?
>
>(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.

    Joe


>
> Vince
>
>
Received on Sat Jul 31 2004 - 09:06:38 BST