Philip Callan said:
P wrote:
| Question: Can I run a 800 FSB Pentium 4 in a ASUS P4C800 board with DDR
| 2700 RAM? Will the CPU automatically clock down to work with the
slower RAM?
|
|
No
The CPU will not clock down, the ratio will go up, and there will be
clock cycles when your CPU is sitting around doing diddly, waiting for
your RAM.
Your DDR333 will clock down to 320Mhz when running with a 800fsb CPU.
Find someone with a lower fsb AMD to buy your PC2700, get yourself at
least PC3200, or your losing some of the very performance upgrading to a
800fsb is supposed to give you.
Philip
To state the situation another way, there is a table in the manual.
It will look something like this:
CPU FSB DDR DIMM Type Memory Frequency
800 MHz PC3200/PC2700*/PC2100 400/333*/266 MHz
533 MHz PC2700/PC2100 333/266 MHz
400 MHz PC2100 266 MHz
*When using 800MHz CPU FSB, PC2700 DDR DIMMs may run only at
320MHz (not 333MHz) due to chipset limitation.
What this says, is if you own a FSB800 processor, then when you place
a PC3200, PC2700, or PC2100 DIMM in the motherboard, and run it
"By SPD", then the BIOS will set the memory frequency to 400,
320, or 266MHz (double data rate) transfer rate respectively.
You could, if you wish, also take a PC3200 memory and run it at
320 or 266, as memory is compatible with speeds lower than its
rating. This would require entering the BIOS and setting the
speed manually.
If your question is based on the premise of reusing your memory
from a previous board, you may see a bigger loss by not installing
ram in matched pairs, as there is a 30% or so difference between
single channel mode (triggered by mismatched ram) and dual
channel mode (paired ram). I measured this difference on a
865GE board I played with before Christmas, using memtest86.
HTH,
Paul
