Hp hdx 18t 8gb ram upgrade fail

I have an HP HDX 18t- 1200 CTO that I custom ordered in 2009 for my wife. Everything on this unit shows it should be upgradeable to 8GB of RAM. I have updated the BIOS to version F.34 which is the newest one on the HP website. I have 2 sticks of Corsair PC3 8500S (1066) RAM that are 4GB Sims. I still have my orignal Samsung RAM which are both 2GB 8500S (1066) Sims. I have installed CPUZ and checked all of the 4 sims. They are pretty much identical down to the timings and everything. The 4GB Corsair Sims both work if I put only one of them in the primary RAM slot the PC boots with 4GB of RAM. It wont boot in the secondary slot with either SIM but will boot with only one of the 2GB Sims in the secondary slot. Im running Win 7 Ultimate So I know its not an OS issue. This BIOS is one of the most standard non changeable BIOS I have ever seen. I am at a total loss as to why it wont read the 4GB SIMS in the second Slot. or together in both slots since they are matched pair. I have seen multiple posts with this same issue all over the internet but no solutions. Even the Motherboard on my unit is the Quenta 3610 withthe PM45 Chipset which uses Both DDR2 and DDR3 RAM and is supposed to be upgradeable to 8GB. I dont understand is it a BIOS Limitation that HP Hosed up?

Have any of you been able to upgrade an HDX 18 with PC3 Memory to 8GB? Anyone have any Ideas what the problem could be here? I will answer any hardware or software related questions. I Just reinstalled a clean install of Windows 7 Ultimate. I have run all the driver Upgrades I can find for the chipset and Bios on HP support site.

 

Just to be clear on this. It currently has 2 PC3 8500s (1066) Samsung chips installed. I can boot the machine with only one of them installed in either slot the primary or secondary slot. I can boot the PC with either of the 4GB Corsair Sims in the Primary slot. Neither will boot in the secondary slot, nor paired together. Both are identical chips. They also have basically identical stats, 204 pin 1066 which matches the Front side bus speed of the MOBO of 1066. etc.. I just don't understand. I've upgraded tons of computers both at my job and at home and I've never seen an issue like this. It's almost as if there is something different about the second RAM slot and its not ment to use 8GB even though from the original specs and guide that came with the machine it says it should be.

 

Best guess? Bad mobo. Seen that before in DV7s with bad mobos.

 

If it was a Bad Mobo why would it recognise the 2GB SIM in the second slot? Why will it boot with both 2GB sims in place and give me 4 GB of RAM. And Both 4GB Sims will boot in the first slot. with the second slot empty. I have searched the interwebs ammong thousands of Posts and it appears that Im not the only one with this issue. I've seen it on another couple of posts here, as well as an HP HDX 16 and 18 posts on HP Official forums. Everyone wanted to blame the RAM in those posts, But Ive tested the SIMS and they are both good. I also have been working on hardware for many years and have never seen a MOBO Bad that would cause only a lower amount of memory to read and not a higher amount.

Just out of curiosity What would make you think its the mobo, in this scenario? I'm by no means selling you short here you may be right.. I'm just wondering what could be wrong with the mobo that would cause it to read only 2GB or lower sims on one of the slots? Thats just strange. The Slots should be paired and read the RAm the same way. since this is a dual channel mobo with only 2 slots.

 

The memory controller failed. That's why dual channel is no longer functioning. For each of the units I was presented with, replacing the motherboard solved this problem. The symptoms were exactly as you describe.

The one thing you can try is to remove the battery, the CMOS battery (usually a CR2032/2016 lithium watch battery) and the AC plug. Then hold down the power button for 30 secs to drain out any excess capacitance. Then replace those items and turn it on.

Otherwise, it's mobo replacement time...

 

Ok. I'll give that a shot. Oddly I've never had any other major issues with this PC and this was the first time it had been reformatted. Plus since it was still reading the original 2GB SIM that was in it originally I thought surely there had to be a BIOS issue or something. But If you have expierienced this before it makes since to me. I've never had the memory controller go out on any of my other units before, so It must be pretty rare. Or else if several people have seen it on these type of notebooks maybe it's a problem with the boards themselves. Thanks for the feedback. I just wanted to make triple sure before I go buying a new Motherboard for it.