Incorrect RAM size reported

[wiputc]

OK, this is not a typical 'incorrect RAM size reported' scenario, where the RAM size reported by the POST screen is almost always lower than the actual RAM.

I was upgrading my old AMD Athlon XP system (but it still runs smoothly) so that it will have a 1.5GB RAM, up 1GB from the former 512MB. The complete specs:
- AMD Athlon XP 2500+ CPU
- Gigabyte GA-7N400-L motherboard
- 2 * 256MB single-side PC3200 400MHz DDR RAM

So I bought two 512MB single-side PC3200 400MHz DDR RAM chips (the difference from the old modules are only of the size - everything else is the same as the old modules - PC3200, 400MHz, single-sided) and proceeded to put them in.

First round, no luck, the PC wouldn't boot. The config is as follows:

dimm 1 256MB dimm 2 512MB (new) dimm 3 256MB dimm 4 512MB (new)

Then I swapped the chips:

dimm 1 512MB dimm 2 256MB dimm 3 512MB dimm 4 256MB

The PC boots, but the POST screen reports a surprising '1792MB', or 256MB more than it should be.

I tried removing one of the older chips:

dimm 1 512MB dimm 2 256MB dimm 3 512MB dimm 4 empty

The POST screen reports correctly, '1280MB' (although now the dual-channel capability is off, because the 256MB chip is unpaired).

I inserted the old 256MB RAM back, and there it goes again, 1792MB.

I haven't installed any OS nor run any RAM test yet, but this is already disturbing.

Anyone had a case similar to this? I tried Google but no luck, the closest case being the RAM size reported lower than the actual RAM.

 

[edfair]

Have you checked out the M/B manual for memory limitations and install requirements? May not help, but at times the manufacturers have put in specific install instructions to get around problems like this.

 

[goombawaho]

BIOS update available????

 

[cdogg]

Filling all 4 DIMM slots can be tricky as you have discovered. Whether or not it is posted in the manual, motherboard manufacturers are faced with limitations that are beyond their control in most circumstances.

One such limitation is the use of single and double rank modules. You can read about it here:

http://www.oempcworld.com/support/Whatis_4-Rank_DIMM_Memory.htm

Basically, there is a particular install sequence you need to follow when mixing single and double rank modules on the same motherboard. This is probably what's going on in your situation. A certain combination is causing the incorrect size to be reported (or in some cases, for it not to boot at all). Disect your mobo's manual to see if it's mentioned. If you're lucky, it will be. The hard part, however, is determining what the old modules are since the "rank" specification is not usually labeled.

By the way, contrary to popular belief the "rank" specification does not mean the number of sides. Usually a double-sided memory DIMM means it's at least double rank, but there's no guarantee that it isn't 4 rank or something else.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Einstein
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[paparazi]

The Nfoce2 chipset (that this motherboard is fitted with)was one of the first dual channel capable chipsets but was extremely fuzzy on memory make/model/type.
Single sided 512mb modules use higher capacity chips, modules like these were a rarity around this era. Fully populated (double sided)512 modules, in my experience, were/are much more compatible with NF2 based motherboards.
Martin

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