> Anyone want to have a go at explaining the difference between parity &
> non-parity RAM?  I just picked up an old 486 DX2 80 and need to throw in
> some more RAM as this only has 4 meg in it.
>
> I have been told that the 486 architecture will only accept Non-Parity but
> a few have told me otherwise.  Non-Parity seems to be tough to find around
> here but Parity is plentiful.  Can they be mixed?
>
> The box will be used as an extra computer for word processing, surfing etc
> and may also be used as a router (Linux) as suggested by others a week or
> so ago.

     Parity is a method by which a computer can detect faulty memory. It
uses an extra bit for every byte, so a 4MB parity module actually has 4MB +
4Mb of memory. This extra bit is set depending on whether the system uses
even or odd parity. In an even parity system the parity bit is set if the
byte in question has an even number of ones. It's the other way around for
odd. This WAS important way back when memory wasn't as reliable as most
wanted (back in the XT days) but these days memory is very reliable. More
advanced systems (servers) must be sure of the integrity of the data going
through them. They will use this extra parity bit for a more complicated
form of error detection and even minor correction and works on a per block
instead of per byte portion.

        Now to you're board. Most 486 boards either did not use parity or gave you
the choice whether to use it or not in the bios. There ARE a few boards that
have parity check enabled, those will require parity memory. In either case
with memory the standard recommendation is get more of what you've got.
However, if you have non-parity memory adding parity memory should NOT pose
any problems. The only problem is if the board autodetects parity memory, if
that's the case simply move the parity memory to another slot until the
autodetect mechanism is looking at you're non-parity memory.

        I have mixed parity and non-parity quite successfully in many systems, you
shouldn't have too many problems with it. Hope this helped. TTYL

        The NOSPIN Group provides a monthly newsletter with great
       tips, information and ideas: NOSPIN-L, The NOSPIN Magazine
           Visit our web site to signup: http://freepctech.com