5 Sep
2005
5 Sep
'05
4:11 p.m.
Date: Sat, 3 Sep 2005 00:17:50 +0100 (BST)
From: ard at p850ug1.demon.co.uk (Tony Duell)
Most, if not all, of the single-bit-wide DRAM
chips (4164, 41256, etc)
had separate DIN and DOUT pins. They were not dual-ported, though, you
only had one address bus for both reading and writing.
Thank you. I have since noted this on X 1 DRAM datasheets. I had
never noticed that before.
You could link these pins together externally, or
you could use them
separately. IIRC on the IBM PC, the DIN and DOUT pins are linked on the
RAMs storing data bits, but wired separately on the RAMs storting the
parity bits.
What is the point in using them separately? Was it for the case
where the destination of a read is different from the source of a
write? I could see where that could happen in parity checking.