PC100 and PC133 RAM modules.....

well running them both at 100 would work, but running them both at 133, might or might not always... depends on the quality of the pc100 i guess..

Mixing pc133 modules with pc100 ones will underclock the pc133 to pc100.

i have 2x 128mb PC133 running at 100mhz (because of the old mobo), all runing fine for about 4 months....about o/c, go ahead, if you are sure of what you should do!

I second that. One of my machines has 1x256 pc133 and 2X32 pc100. The other has 2x62 pc100 and 2x16 EDO. No problems whatsoever.

I recently bought a 128MB PC-133 stick. I used that one and then inserted an old PC-100 32MB stick. I benchmarked it (just Norton Utilities' System Information) and my total score dropped about 8 points from when my PC had 128MB at PC-133 to to when it had 160MB at PC-100.

If your PC-100 stick is not much (in terms of size) compared to the PC-133 sticks, then I guess that you should just use the PC-133 sticks. But if the PC-100 sticks are large enough, then more probably than not you'll get a performance boost even when the PC-133's are degraded to PC-100's.

hmm cool.. so I just leave my 128mb pc100 ram in there.. and put both 256 sticks on either side.. being that my MB is pc100 it should auto cut it down..

Originally posted by BaD_BURN
Mixing pc133 modules with pc100 ones will underclock the pc133 to pc100.

Click to expand...

Only if the motherboard is reading the SPD info, and acting upon it.

Originally posted by dzx
hmm cool.. so I just leave my 128mb pc100 ram in there.. and put both 256 sticks on either side.. being that my MB is pc100 it should auto cut it down..

Click to expand...

Some motherboards/chipsets are picky about the order in which dimms are inserted into the mainboard, and their size/configuration. Grab the latest manual for your board from the manufacturers website first and have a look.

And anyway, why not just use 512Mb at 133Mhz? That's going to be a better deal than using the extra 128, but cutting the speed down 33Mhz. Unless you're /really/ starved for memory, which i doubt.

my MB manual states nothing about using pc133 only pc100

It's probably getting on a bit now then, you may find you need to shuffle the sticks around until you find an order it likes. Course, it may work just fine going 256, 128, 256.

Stick 'em in and see