768MB but not 1GB?

[Cherub (a.k.a. Steve L.)]

As you may recall, 2 weeks ago I bought two 512MB DDR PC3200 memory sticks for my Medion desktop (P4 2.66GHz, only 2 DDR memory slots). I removed the 256MB (PC2700) stick, installed both 512's, then panicked! The CPU memory test showed the full 1GB, then booted into XP, then hung. Repeatedly.

I removed both 512's, reinstalled my original 256MB, and everything was fine.

I added one 512MB to the original 256M, everything still fine. (Didn't seem to matter which stick was in which slot -- ended up with 512 to the right (slot 0?) and 256 in other).

I swapped the second 512 for the 256, back to bad.

I have used EACH 512 with the 256, so I know BOTH 512's are good.

Why can't I use both 512's together???

[Cherub (a.k.a. Steve L.)]

BTW, this machine DOES seem to run much better w/768 than 256.

[Cherub (a.k.a. Steve L.)]

"I see!" exclaimed the blind carpenter, as he picked up his hammer and saw, a.k.a. Steve's ongoing computer memory saga.

BestBuy will take back one or both of my DDR memory sticks until 4/10.

I'm pretty sure I now understand why the supposedly backward compatible PC3200 memory won't run w/o my existing PC2700 memory. I assumed that because the Medion had PC2700 memory, it had a 166MHz bus. Not true!
According to CPU-Z, the Medion has a bus speed of 133.6 MHz.
At 133MHz, the new DDR is different (slower?))!

CAS# RAS# to RAS# Tras
Latency CAS# Precharge

256MB PC2700 2.0 3 3 6

512MB PC3200 2.0 2 2 6


Yesterday (Wed.) afternoon I drove out to BB. A wasted trip. They had 512MB PC2700 Kingston for $80, but would it work better than the $40 PNY? Last night I noticed BestBuy had a 1GB PC3200/PC2700 DDR in last Sunday's ad (lower left, pg. 21) for $80. the same price as my two 512's. Would a swap be better, or worse? Right now I have 768MB (my old 256, plus one of the new 512 sticks) working fine. I almost returned the other 512 for credit, but then decided the pair of 512's would be more valuable to someone willing/able to trade for memory I can use.

What do you think? Got any memory to swap with me? I MUST get this done prior to Tue. 4/10.

--Steve