Altair parts substitutions

From: John Wilson <wilson_at_dbit.dbit.com>
Date: Tue May 23 11:40:23 2000

On Tue, May 23, 2000 at 08:50:52AM -0400, Cini, Richard wrote:
> This is what I meant exactly - no bi-directional data bus. I'm guessing that
> there is a fine distinction between dual-ported and separate input and
> output busses...

Um, it's a *big* difference! Dual-ported means two separate ports that you
can use at the same time. Separate in/out just means no need to disable
the chip's drivers when writing to the memory. Faking separate I/O using
bidir parts plus external buffers is easy. Faking DP using regular RAMs is
a bigger deal, you need some kind of arbitration and something to generate
mem cycle timing 2+ times as fast as the two busses that are attached. Still
could be cheaper than truly dual-ported memory though, especially if you need
something big but not too fast.

John Wilson
D Bit
Received on Tue May 23 2000 - 11:40:23 BST