What would happen if I put 256mb PC133mhz in a motherboard that only supported PC100??? I think its cutting my memory in half and only giving me 128mb instead of 256

If it works it will underclock to the slower speed of the PC100, it will not decrease the amount of RAM.

Motherboard of that age were some times picky about what RAM they liked.

well like the manuel says that I could have up to 1gb of RAM, I should have 512??? I have 2 64mb's, 1 128mb, and 1 256mb sticks, and its only measuring the 256 as 128 giving me 384???

Depending on where you are reading this figure you could be seeing the amount under utilization. For example, if I look under system properties it only show that I have 981,476KB of RAM out of the 1024MB that I know is there.

Then again if you are using something like SIW it will show the total amount and the individual module's amount. If you don't have this, download it and give it a spin. The 64MB is the size of you smallest module, so it could be that it is bad. The SIW (System Information for Windows) will no show the module if it is bad.

yea.....the 384mb is in System Properties,

I never thought about the 64mb being bad modules...ill look into that...

Did you download the SIW and look to see what it listed for you total and individual modules?

I should have added this originally...it's a free download.

SIW is such a cool application! Shows you everything on your computer! Its so useful! Thanks
-Jake

use memtest86 to check for bad ram maybe?

some pcs have a max ram per slot

e.g my old pc has max total ram of 384mb and max per slot of 128

so i had:

256
256

and it effectively wasted 128mb of ram

SIW will show the maximum capacity, it will also show how many expansion slots there are, divide the capacity by the number of slots for the maximum capacity for each slot.

With a motherboard that uses PC100 and PC133 there are a couple of potential problems with RAM. Some motherboards are picky about what RAM they like, my MSI K7 Pro didn't like high density modules. Some motherboards are specific where they want to see the larger modules, like the larger module should go in the first slot.

If you download the SIW it will take a lot of the guess work out, after that you will know if the amount represents what you have installed. If you are still missing that 64MB try removing all but one module and trying each one separately.

Ok i did the SIW audit. I came up and said that the maximum capacity is 1024mb for 4 slots of ram. ( 1024 / 4 = 256) So it is still saying that my 256mb stick is being read as a 128mb stick.