As an early Christmas present to myself I decided to upgrade my main workstation to 8GB RAM. It already runs with 4Gb quite well – but with SQL server, Visual Studio and a couple of Virtual PC sessions running things start to get crowded.
To play on the safe side I bought exactly the same model of memory as I currently have – some 2GB DDR2 DIMMs from OCZ. However on installation of these I found Vista x64 was very unstable, blue screening randomly several times in the first day.
I booted up a CD with MemTest and immediately had lots of memory errors. I removed the new memory, and reran MemTest – this time no errors. It seemed like a clear case of faulty memory, so I obtained an RMA received some new chips of the same type.
Amazingly, I got errors and blue screens again, so out came MemTest to test the full 8GB – same result: memory errors. However this time I was suspicious that not all was as it seemed, so I took out my old 4GB, and put the new chips only into their slots, so I was only using the new ones. MemTest this time passed without problems. Hmmmmm.
Second test was to put the old 4GB back in, but in the other slots. MemTest errors again. So this leads to two possible causes – (a) that the second pair of DIMM slots were faulty or damaged, or (b) that something else might be at fault – possibly the BIOS?
If (a) it would mean a new motherboard, and a warranty return and a week or two without my main workstation, so I had to eliminate (b) first.
My motherboard is an Asus P5NT-WS which is pretty unique in supporting SLI on PCI-express and has a single PCI-X slot which I used for the Areca 1120 RAID controller. The current BIOS was pretty much unchanged since I bought it (version 0702 I think), so I downloaded the latest one (1104). Fortunately Asus allows use of USB drive updates, so using Alt-F2 at boot you can flash the BIOS quite easily. I did this with only 4GB of memory in so that I wasn’t going to get any corrupt BIOS issues.
On restart, I got nothing – no boot, no beeps, no screen. I tried a few things and eventually decided I had to clear the NVRAM (the battery backed BIOS configuration data). Hurray the machine rebooted and I was able to tweak the BIOS settings. I run without any overclocking at present so this was not an issue.
Having got a stable booting Vista at 4GB, I re-added the new 4GB to make it 8Gb and presto, no more memory errors. A full 90 minute MemTest ran flawlessly.
So if you have an Asus P5NT-WS and have issues with more than 4GB RAM, check the BIOS updates first!