4GB memory POST problem

[Braxus]

I got four 1GB registered ECC sticks here (36 chips/Low profile stacked) and for some odd reason, when I add the 4th 1GB stick in, it fails to POST. Interestingly enough, if I plug in an 18 chip 256MB stick on the 4th slot (~3.3GB total) the system boots up fine. The board I'm using is a Tyan Tiger MP (S2460).

Any one have any thoughts on this?

Only thing I can think of is that the board can't supply enough juice to power a total of 144 memory chips (36 each stick). Not sure on this theory however.

 

[Boonesmi]

is the bios up to date?

it seems like when the board first came out they had problems when all the dimm slots were filled, and it was fixed with a bios update

 

[Braxus]

Yeah, using the latesest rev. 1.05 here.

 

[wlee]

Have you tried swapping the order of the chips ? Have you tried them one at a time, and in pairs ?

 

[InlineFive]

Some motherboards are picky about if the last memory slot is populated with Single or Double-Sided memory.

 

[Slogun]

I remember reading on this forum recently that 4GB is not the actual memory limit but rather something like 3.5GB due to architiecture constraints.

Put a stick of 512 in that last slot and it may work.

 

[Braxus]

That limit above 3.5GB is reserved for PCI devices (at least for the AMD MP chipset). As for the memory, tried the usual stuff, swapping, testing (all tested good with RST & memtest86), etc. Plugging in a fourth 36 chip stick just makes the board not want to play.

Also, another thing I've noticed. The memory tends to get VERY hot after a while given there are two chips stacked on top of each other. Measured it and it seems to be floating around the 49C/120F mark. Any recommendations for ramsinks? Those clipon plates (e.g. thermaltake) don't seem to work as it doesn't really fit the module too well.

 

[Boonesmi]

a small fan set to blow down on the ram will keep it nice and cool... it doesnt need to be a big or loud fan it just needs to move a little air

 

[Peter]

Well, in fact, with Athlon MP being a pure 32-bit CPU, the _entire_ address space is 4 Gigabytes. Your BIOS ROM, PCI and AGP devices as well as a handful of other system essentials already reside at the top end. So even if the board lets you put in 4 GBytes of RAM, you're not going to be able to use all of it. Put 3.5 gigs in and stop worrying about how to get it to boot with 4 - it won't have any practical use.

 

[Peter]

This btw is one of the reasons for the move to 64 bits. The initial wave of 64-bit AMD processors has a 40-bit address space, or one Terabyte. That'll do for a while ...