When describing RAM, what do low density and double-sided mean, and how can I determine whether my system requires these features?

A memory module is made up of circuitry and memory chips. Take a 128MB module for example. The total memory capacity is 128MBs but can be made of 8 16MB chips in one configuration of maybe 16 8MB chips in a double sided configuration. The chipset on your motherboard was designed to work with the technology of the day. Individual chips have gotten bigger (denser) over time. If the highest density chip was 8MB at the time your motherboard chipset was designed, your motherboard may have trouble accessing a module with the higher density chips (8 x 16). To try and determine what memory the chipset/motherboard can handle, you can read the manual and make some determinations from that info. If, for instance your MB has 4 memory slots and the manual states the total memory capacity is 512MBs, then 512/4 = 128MB per slot. You still don't know what chip configuration that 128MB can be. But if the 128 is low density, then it will be double sided and high density single sided. Beyond that, what I do with an unfamiliar board is reference the chipset manufacturer. THis is because the MB manufacturer can only do what the chipset allows, or less, not more. Other folks here that are more knowledgable than myself can elaborate on, or correct my post. Hope this gives you a basic understanding.

Thanks OtheHill. Therefore my PIII would require double-sided, low-density RAM.

That, I am not sure of, as I am not up to speed on the various chipsets for Intel boards. Hang in there, someone else should come along that can say for sure.

I help U is my name, and memory support is my game! So you have a PIII motherboard, do you have a model number? I could then research it and tell you what your chipset can handle. :)

Here is some information I found by visual inspection of my motherboard: Legend QDI BrillianX 8V VIA VT82C692BX VIA VT82C596 Hope this helps.

You are using a BX type motherboard but with VIA chipsets. An older board it is! You will definitely need low-density RAM. Stick to memory built with 64Mbit chips, PC133 should be fine. If you are buying a 256MB , make sure the seller has a double-sided module using 16x8 structured chips. Buying the single sided modules in the market nowadays will only read 1/2 in your system. 128MB modules will be single-sided but with 8 chips on them. Sorry for the late reply! :)