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12 sticks of 30-pin 256K (9 chip) parity SIMM's

Re: 12 sticks of 30-pin 256K (9 chip) parity SIMM's

"Super-Slasher" wrote:

> If anyone has 12 sticks of these SIMM's lying
> around and don't plan on using them, please!
> get in touch with me.

> They MUST be parity.
> They MUST be 256K.
> They MUST be ... umm... RAM. Yeah! hehe

That MUST be picky! ;-)
 
Re: 12 sticks of 30-pin 256K (9 chip) parity SIMM's

"Super-Slasher" wrote:

>> That MUST be picky! ;-)

> Hehe, that's all that will run in my IBM PC AT.
> It's not me that's picky; the computer is.

Ah okay, I thought you were running OS/2 or
something, that would have to be V1.xx of OS/2 &
3 Mb seems enough. But I've only found
problems with memory in OS/2 Warp (v3.xx)

Cheers,
CP/M User.
 
Actually, you can stick non-parity RAM in the AT. I thought the non-parity stuff had a 'parity bit generator' on the stick so that it would be usable.

That being said, non-parity memory sucks. I'd like to know if I have a single-bit error, even if there isn't much I can do about it.

(I just bought 4 16MB 30 pin SIMMs for my 486. It's always had parity RAM before - these are non-parity. I'll run the machine for a bit, make sure it's stable, and then take my chances.)
 
"mbbrutman" wrote:

> (I just bought 4 16MB 30 pin SIMMs for my
> 486. It's always had parity RAM before -
> these are non-parity. I'll run the machine
> for a bit, make sure it's stable, and then
> take my chances.)

Geez, did that set you back a bit. A while ago
I saw some 16Mb 30 pin SIMMs which they
were asking around $125 for 1.

However, I'm just a bit curious as to the
difference between Parity RAM & non-Parity
RAM, is Parity RAM quicker or something?

Cheers.
 
CP/M User said:
However, I'm just a bit curious as to the
difference between Parity RAM & non-Parity
RAM, is Parity RAM quicker or something?

Cheers.
Click to expand...

Parity ram does a primitive form of error checking by using an extra bit which is either set or reset depending on whether the eight bits of the byte add up to an even number or odd. If the parity bit doesn't agree with what is expected, then the byte may be re-written. That is why parity ram has 9 chips; eight for the actual date byte and one to hold the parity bit. It isn't necessarily faster, just more accurate. (In fact, it may be slower if it has to do a number of re-writes.)

--T
 
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