Altair parts substitutions

From: Dwight Elvey <elvey_at_hal.com>
Date: Tue May 23 19:17:04 2000

Eric Smith <eric_at_brouhaha.com> 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...
>
> Specifically, a true dual-ported RAM chip has separate address busses and
> control signals/strobes (*RD and *WR, or *CS and R/*W, or the like) for
> each port.
>
> Dual-port RAM chips tend to be expensive and not very high-density, so
> they aren't commonly found in commodity computer hardware. It's usually
> more cost-effective to time-multiplex a single port.
>
> Current manufacturers of dual-port RAM chips include Cypress and IDT.
> There are even some quad-port RAM chips now.

 Most of the dual ported RAM chips that I know of were used
on video boards. These had parallel I/O on one side and
serial I/O on the other.
 In the microprocessor designs we do, we designate the RAMs
as follows:

 1RW Single port/ may have separate in and out busses
 1R1W Dual port. Separate addressing for read and write
 5R5W Multiport. A real pain to test {:-0>

 We do use quite a few multiported RAM as internal design
but it would be hard to use these as single chips.
Dwight
Received on Tue May 23 2000 - 19:17:04 BST

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