a classiccmp electronics project?

From: Joe R. <rigdonj_at_cfl.rr.com>
Date: Sat Jul 31 09:02:36 2004

At 05:26 PM 7/30/04 -0700, you wrote:
>> OK. I was thinking about the microcode ROMs in an HP9810 (somethign that
>> _I_ am working on, and those are most certainly 'hit' as soon as INIT is
>> deaseserted and the microocde program counter starts to change. I prefer
>> to think of general-purpose solutions (i.e. somethign that will replace
>> every 256*4 ROM), rather than soemthing that works only in specific
>> machines under specific circumstances.
>
>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.

  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.

     Joe


>
> Vince
>
>
Received on Sat Jul 31 2004 - 09:02:36 BST