This is pretty frustrating.
A friend of mine brought back some 2gb DDR2 modules from USA for me:
Kingston ddr2 800mhz and I also had some 2gb 667mhz versions here.
Each module tests 100% ok individually but when added to a mobo as 2 x 2gb the bios is either showing 2.4gb or just over 3 gb.
When I combine 1 x 2gb and 1 x 1gb the bios is showing just over 2gb and I get a bsod. I don't get a bsod when combining 2 x 2gb though, as i would expect.
This is pre-Windows of course, however from the screenshots included here, Windows picks up the physical 4gb but reflects what the bios shows shows as the useable amounts.
I've tried combing only 667mhz together, 667mhz with 800mhz together and the results are exactly the same.
This happens on two entirely different brands of mobo, both with only 2 mem banks and Intel based sockets.
Could it be that BOTH have memory controller problems? Faulty slots? (individually, each slot functions normally)
I've tried this with and without a GPU, thinking that the shared mem might be an issue, but whoever heard of 1gb+ shared memory?
Am I doing something wrong here?
RAM can be fickle and I am certainly no expert.
Just to clarify - the 2 mobos you've tested both have only two RAM slots, yes? I am double checking that detail because it definitely sounds like the sort of symptom one would expect from inserting 2 RAM strips into the wrong slots on a 4 or 6 slot mobo.
Have you checked the RAM stats shown in Resource Monitor? Resource Monitor will break down installed RAM into different categories... what is showing under "Hardware Reserved"?
Moderators
Are you saying you have two ram banks with four slots? Or one ram bank with two slots? If you have two ram banks with four slots then make sure ram is installed in slot one or slot two on each bank. I also like to install matching pairs of ram in their respective slots. I have installed different ram size and brands but I always try and match the ram.
Each mobo has just 2 ram slots.
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Marc Thomas said
Each mobo has just 2 ram slots.
I do not know the mobo brand but all the two slot mobo that I have had experience with would only support 2GB in dual channel mode and I have had to set dual channel mode on a couple of machines I have worked on. Other than that then I would try each stick of ram in each slot separately.
Daniel, both mobos support a max of 4Gb and yes, I have tested each stick separately and run Memtest on each with no failures.
This all points to dodgy mobos imho.
Moderators
I have been doing some google research on this the past few days. It seems you are not alone with this problem and it seems it is more common with mobo's that have one bank and two slots for a max of 4gb. Now, I do not understand all the comments but it seems these mobo's have a problem with hardware mapping, whatever that means. It also seems like the problem cure's itself after a few reboots and for others it has required a bios update. I will say that it affected more Asus mobo's than any other brand. Daniel.
Thanks for thinking on this Daniel.
The two mobos concerned are Gigabyte and Biostar, both have the latest bios update and have been bios cleared numerous times.
Clearly this isn't a Windows issue as you know and I can only put it down to a fault in each mobo, barring any further explanations.
Coincidentally, I added another 2Gb to my little HP Mini Slimline connected to the TV, bringing it up to 4Gb with no problems at all.
The memory modules are all fine, hence my rather ham fisted deduction.
My guess would be BIOS followed by different specs for the DIMMs - probably voltage or timing.
According to Biostar and Gigabyte support pages for P4M900 and GA-VA900M, Kingston 2Gb KVR800D2N6/2G sticks aren't supported.
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Marc, I usually use the Crucial web site to search for compatible ram. Daniel.
Thanks Daniel. but that only shows Crucial memory compatibility and due to the f**ing restrictions here, I can't buy it.
Oddly though, the 2gb sticks work fine individually in each mobo in spite of not being on the compatibility lists, but not when paired with another 2gb stick or 1gb stick (compatible).
Apologies, for posting to such an old thread, but I do hope this will be read, and maybe help someone in the future.
I too am NO RAM Expert, but, I did work with a ram expert at the Market Pro Computer shows, which used to play here in Florida, about once a month.
Working with a true RAM Expert, gave me a really good insight into the entire world of RAM memory, like what works and what doesn't....what's good and what's BAD.
If there is ONE thing I learned, that has served me well, is to NEVER buy Kingston ram or any Kingston product. Kingston buys ram from major manufacturers, that has not passed final reliability testing. So it may work for a while and then fail.
Since I always Guarantee my work, I wouldn't dream of ever putting Kingston ram into a customer's PC.
Recently, I was brought a Laptop PC to refurbish. Part of that job was to reinstall the OS from a DVD. The install would get up to 87%, loading files and then crash. I cleaned the DVD and tried it several more times just to make sure what I was seeing. I even tried using an external DVD player. Sure enough, the install crashed at the same point every time.
So I took out the RAM to clean it and I was horrified to find the second SODIMM was a Kingston. (That was added by the owner.) I removed that stick of ram and the install went through without any hesitation, running on just the original 2GB of ram.
I don't know anything about the limitations of buying things from the US, in Argentina, but if I had a choice, I'd try to get only Crucial ram. It's assembled using only top quality "Micron" memory. Some retail/wholesale stores also carry it. I can buy it in Orlando.
Cheers Mates and Happy Computing!
TechnoMage 
A man with experience is never at the mercy of a man with an argument.
Moderators
The only PC I have that isn't running Crucial ram is the one I am using right now. When I built this machine, and to show my Wife a good time we traveled to Dallas, TX to shop at a Tiger Direct store, I was like a the proverbial blind dog in a meat house, my Wife?????. Anyway the store did not have any Crucial ram but they did have 8GB of Kingston and that is what I bought, but it has did well. Daniel.
TechnoMage said
Apologies, for posting to such an old thread, but I do hope this will be read, and maybe help someone in the future.I too am NO RAM Expert, but, I did work with a ram expert at the Market Pro Computer shows, which used to play here in Florida, about once a month.
Working with a true RAM Expert, gave me a really good insight into the entire world of RAM memory, like what works and what doesn't....what's good and what's BAD.
If there is ONE thing I learned, that has served me well, is to NEVER buy Kingston ram or any Kingston product. Kingston buys ram from major manufacturers, that has not passed final reliability testing. So it may work for a while and then fail.
Since I always Guarantee my work, I wouldn't dream of ever putting Kingston ram into a customer's PC.
Recently, I was brought a Laptop PC to refurbish. Part of that job was to reinstall the OS from a DVD. The install would get up to 87%, loading files and then crash. I cleaned the DVD and tried it several more times just to make sure what I was seeing. I even tried using an external DVD player. Sure enough, the install crashed at the same point every time.
So I took out the RAM to clean it and I was horrified to find the second SODIMM was a Kingston. (That was added by the owner.) I removed that stick of ram and the install went through without any hesitation, running on just the original 2GB of ram.I don't know anything about the limitations of buying things from the US, in Argentina, but if I had a choice, I'd try to get only Crucial ram. It's assembled using only top quality "Micron" memory. Some retail/wholesale stores also carry it. I can buy it in Orlando.
Cheers Mates and Happy Computing!
TechnoMage
Well that's odd!
I've been using Kingston RAM for donkey's years and this is the first time I've heard about Kingston RAM being crap.
I have the brand installed over several machines, albeit DDR3 and I'm inclined to believe that my problem was a DDR2 compatibility problem with the two motherboards in question which I have now sold anyway with 2Gb each so I can't test that theory with Crucial RAM, but I will at the nearest opportunity.
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