Motherboard only recognises half of RAM

[skodaman]

I have an old Daewoo Motherboard (CB652M LX for which I have no manual)with a Celeron 433MHz processor and have just bought some more PC100 DIMMS for it.

If I put a single 512MB DIMM in it the BIOS recognises only 256MB
If I put a single 256MB DIMM in it the BIOS recognises only 128MB
If I put 2 256MB DIMMS in it then the BIOS only recognises 256MB.

It seams as though I only get half the memory of what I put in!

I can accept that there may be a maximum value of DIMM but this does not appear to be what is happening.

Does anyone have any ideas?

[Fruss Tray Ted]

Welcome to http://www.pcguide.com/ubb/pcgubb.gif

You might be able to find a manual online, not sure.

But most likely you are trying double sided RAM in a motherboard that only supports single sided. The manual would tell you that if you find one. Go to Google and type in your make and model. It should come back with something that will lead you to one.

[skodaman]

Thanks, but unfortunately the 256MB DIMMS were single sided and I've hunted high and low on the internet.

[mjc]

Some boards have a maximum per slot...if you can get a couple 128MB sticks to try see if it will recognise all of it then.

[Sylvander]

See this
http://www.abc.kharkov.ua:8101/mother/daewoo/652.html

I couldn't find a manual.

[rond36]

Check out this thread (http://www.pcguide.com/vb/showthread.php?s=&threadid=23387) it is the PC problem that brought me to these forums. An Intel 440LX chipset motherboard that was missing half of the installed RAM. Your motherboard was made before the PC100 spec was fully adopted. 440LX motherboards can only use PC66 or PC100 2 stepping SDRAM. I think that you have made the same mistake that I did and installed 4 stepping RAM and the BIOS can only see half of it.

Here is what Crucial has to say about 2 and 4 stepping RAM:

The PC100 standard specifies 4-clock memory. For a brief period of time before the PC100 standard came into use, a couple of computer manufacturers built systems that took 2-clock memory. Crucial offers 2-clock memory for the very few systems that require it, but the vast majority of the SDRAM we sell is 4-clock memory.


2-clock SDRAM was the first generation of SDRAM that used 2 CK, or Clock lines, to synchronize the memory chips with the motherboard. Systems that require 2-clock SDRAM won't accept 4- clock SDRAM and vice versa.

Physically looking at a memory module, there really is not a distinguishing mark to determine if the module is 2-clock SDRAM or 4-clock SDRAM. The only way to distinguish the two parts is through the part number markings or data sheets supplied by the manufacturer.

Your motherboard is not listed by the Crucial Memory Selector.