Difference bewteen PC2100 and PC2700 Memory

[Dick Sutton]

I know that this is a hardware question, but it relates to another thread
that I have going concerning a possible memory problem with XP Home
("Computer beep-beeps").

The reason I ask is that my bios says I have PC2100 type memory installed
(from the manufacturer) while the motherboard info says use DDR PC2700 184
pin DIMM's. In addition, I checked the www.crucial.com site and they
indicate that my model # pc should use 184 pin DDR PC2700 DIMMs.

The specs look identical on each DIMM, so what's the difference? There must
be one...

Dick

 

[Rich Barry]

Dick, the difference is that the PC2700 can run at a faster front bus
speed and memory speed. I have PC2100 in mine
and it runs at 133mhz. The 27 can run at 166mhz. You multiply those
values by 2 to get the 266 and 333 effective values.
So, your problem might be that the 2100 Ram you are using is set to 166
and can't handle that speed. These are all enabled
in the Bios. The 21 will run Ok as long as you stay within it's
parameters. On most motherboards today you can adjust the
FSB to 166 and have the memory run at 133. Sometimes you can overclock
the 21 Memory to run at faster speed but
that's another story.

 

[Dick Sutton]

Thanks Rich,

I would guess then, that I shouldn't mix these two types. That is if I have
two slots and one is in use and is PC2100, must the 2nd slot be PC2100 also
or can it be PC2700?

Dick

 

[Richard Urban [MVP]]

If your M/B specs PC2700 RAM, and you have both PC2100 and PC2700 installed,
you must manually adjust the M/B bios to be compatible with the PC2100. If
you don't, and adjust the M/B FSB (front side bus) speed for PC2700, the
PC2100 RAM may lock up the computer.

This is because you will, in effect, be overclocking the PC2100 RAM. Your
system may not like that and cause boot problems or other stability issues.

--
Regards,

Richard Urban
Microsoft MVP Windows Shell/User

Quote from: George Ankner
"If you knew as much as you thought you know,
You would realize that you don't know what you thought you knew!"

 

[NotMe]

With the older memory going UP in price, you might be able to buy a stick of
PC 2700 twice the size of your existing stick of PC 2100 for very little
more than buying a matching stick of PC 2100. I'd shop around before I
decided.

 

[Lil' Dave]

In a nutshell, its better not to mix the two. Especially if one bank is
tied to two RAM slots.
The PC will probably adjust by using a slower (higher number) column/address
refresh rate for the faster RAM. But, will slow down the slower RAM in the
adjustment if the slower RAM is retained.