[plug] (OT) - Hardware - Motherboard and RAM

[Brian Tombleson]

From: "Andrew Simmonds" <simm0 at ii.net>
> > navarre at plug.linux.org.au wrote:
> > > I would not attempt to mix EDO and SD RAM but on looking at
> > > your message I think you are using 64 Megs SD RAM.
> >
> > I've never had problems mixing EDO and SD, but given that the EDO is
> > likely to be much smaller and sure to be much slower, there seems to be
> > little point. SD is a cheap as chups these days anyway. Unless I have
> > good reason to I no longer bother installing less than 256MB.
> > Cheers;
>
> u sure? from memory EDO can only be put in pairs and is a compleatly
> different memory architecture.

Sort of, so I'll give you my understanding :) ..

The requirement for pairs is a function of the motherboards, not the RAM.
The Pentium class motherboards and nearly all of them up until they were
only coming with SD-RAM slots used a memory interleaving system that
required the banks to be filled in pairs where (literally) memory address
"0" would be on the first bank and memory address "1" would be on the
second, "3" is on the first, "4" is on the second, etc...  You could take
the same 72-pin EDO RAM and stick (one of) it in your old 486 (which didn't
user interleaving) and it would function quite happily with just a single
stick.

The "concurrent SD + EDO RAM" question again is a functional capability of
your motherboard (or not, as the case may be).  The first ones to come out
you couldn't have both types in because it did not handle the difference in
timing well.  Latter models that still supported both type of RAM overcame
this problem and in general, most of the time, you could run both types
concurrently.

Navarre still has it correct though because if your MB supports SD-RAM, it's
so damn cheap to just throw a heap more in that finding and using EDO RAM is
a bit of  a waste of time.  If you have EDO, save it for the machine that
don't have SD slots.

Just my thoughts.

- Brian.