Can't POST with all (3) DIMM slots full

[DimM]

P4B533 mobo in a year+ old Alienware-built computer will not post after filling all 3 DIMM slots.

Using two identical 256 PC2100 sticks that came with the Alienware, and a recently bought 512 stick that was advertised as PC2100 but diagnostics reveal it as PC2700U (?). When any two of the sticks are used in any two DIMM slots out of the three, the computer will boot fine. Memtest insists all three of the individual sticks are fine.

However, when all 3 DIMM slots are full the computer will not post. This leaves me with only being able to fill two slots for 768mb of RAM instead of all three for a gig.

Can anyone please help?

 

[mechBgon]

Sounds like you're trying to run six banks on a four-bank chipset there, my friend Consult page 2-11 of your manual for the reason, but the bottom line is you should unload those two 256's for another 512, and put your two 512's in slots 1 & 2.

Welcome to the Forums, hope that was some help

 

[DimM]

Thanks!

 

[Cheetah8799]

While I think you *should* be able to run 3 sticks, there wouldn't be 3 slots if it wasn't meant to work, maybe the mobo just doesn't like that combination of ram for some reason. Try selling your 256mb sticks in the FS/FT forum and buy another 512mb stick to match the one you have now.

 

[Unforgiven]

Originally posted by: Cheetah8799
While I think you *should* be able to run 3 sticks, there wouldn't be 3 slots if it wasn't meant to work, maybe the mobo just doesn't like that combination of ram for some reason. Try selling your 256mb sticks in the FS/FT forum and buy another 512mb stick to match the one you have now.

i agree with that 100%. most likely its a ram configuration problem and not a problem with the 3 physical slots. ive had similar issues with another machine in which memtest reported no errors at all but when i had all 3 sticks in together i was screwed.

 

[mechBgon]

The Intel i845 chipset is inherently limited to four banks of RAM. If his 256's were single-sided, then it could work (two single-sided in slots 2 & 3 plus his double-sided 512 in slot 1). The manual goes into that.