23 May
2000
23 May
'00
7:17 p.m.
Eric Smith <eric(a)brouhaha.com> wrote:
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
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.