Pentium 4 CPU - DDR compatibility

[Jarod]

Hello all, quick question: Would a PC2100 DDR266 memory module be
incompatible with a Pentium 4 2.6 Ghz CPU with FSB speed of 800MHz
(assuming the motherboard is compatible with both), and would it be
compatible if the processor was the FSB 533MHz version? And if you can
answer that one, maybe you can tell me how compatibility is determined
from all those numbers. I'm trying to get a new CPU-motherboard-DDR
combo working and I suspect it may be a mismatch between the CPU and
the DDR I've got.

 

[DaveW]

You need DDR 400; not 266.

 

[kony]

Hello all, quick question: Would a PC2100 DDR266 memory module be
incompatible with a Pentium 4 2.6 Ghz CPU with FSB speed of 800MHz
(assuming the motherboard is compatible with both), and would it be
compatible if the processor was the FSB 533MHz version? And if you can
answer that one, maybe you can tell me how compatibility is determined
from all those numbers. I'm trying to get a new CPU-motherboard-DDR
combo working and I suspect it may be a mismatch between the CPU and
the DDR I've got.

PC2100 memory runs on a 133MHz clock-rate bus at DDR "speed". The P4
bus is quad-pumped (4X).

Assuming you want synchronous memory and FSB speed (at the very least,
you don't want a slower memory bus clock rate than FSB clock rate),
this means PC2100 memory is suited for 4 x 133 = 533MHz FSB version of
the P4, or any P4 & Celeron with FSB <= 533.

You'e right, PC2100 memory isn't suited for a P4 with 800 "MHz" FSB,
which is 200MHz FSB clock rate, quad-pumped.

For the "PC" rating of the memory you would need for that P4 w/800FSB,
take the clock-rate frequency, 200MHz, multiplied by 16, = 3200
(PC3200).