Physical memory 4gb - Installed 8gb

Does the BIOS see 8GB on POST and in the CMOS screen?

Under control panel - system Does it show 8GB?
Which version of Windows and Service pack are on that screen?

Do you have have ACPI enabled?
Do you have the memory hole enabled?

Does the motherboard rev support the RAM?

I have a Tyan Thunder K8W rev 3.xxx board that does not support dual cores. Only rev 4.xxx does.

Vista64, Gigabyte motherboard using DDR3 RAM, 4 X 2 GB 'sticks' made by GSkill.

Some *specific* hardware specs would help eliminate doubt here but what I wrote above answers some of your questions, Michael.

It could be a conflict with CMOS setting or the spec level of the memory modules. I just bought 8 x 2GB Kingston. I had to make sure the spec of the build was proper for my Supermicro X7DWA-N board. Did you try removing one of them and seeing if 6GB works properly? Did you verify the 8 sides of ram is possible. Some board only go up to 6 sides of ram and require single sided ram. I work with server boards. They are very picky on ram spec.

In your BIOS there is a setting to Remap Memory, that has to be enabled. This allows the system to remap the memory over 4G's because Vista x64 does not handle the addressing correctly over 4G's. You don't have to reset your CAS timings, or any other memory timings here, the default timings of your RAM will work just fine.

dmex is a bit mixed up actually, the Remap feature is only designed to be used on the 64bit systems and should be disabled on a 32bit system. At least that's what my Asus MB's directions point out, and I had to use the memory Remap to get all my RAM going.
He's right on MB utilities working on Vista tho...yikes...that's been fun for allot of MB makers for the first while, they seem t have a better handle on things lately but some still are actually dangerous. The ASUS EZ Flash, BIOS Flash utility has been killing ASUS boards left & right so they now recommend only using the Floppy or command line utility for flashing.

Do what? I have never heard this before. A 64bit OS *should* has no problem access over 4 GB of RAM - in fact, it should be able to access 2^64 bits of RAM....

Very strange that ASUS has this in their boards.

Mind you, not calling you a liar or anything like that - just absolutely astounded that this even holds true. After all, I built machine with the intent of using 8 GB of RAM and Vista 64bit in the first place....

Vista 64bit is well known to have had an issue with handling over 3G's of RAM properly, it was a well hashed over problem for many users at the start of Vista's life. Most people with TV Tuner cards had only Green Screens with anything over 3G's of RAM on Vista 64bit because of the way Vista handled the addressing of the extra RAM.
Yes, you have to have a 64bit OS to address 4G's of RAM or more, but Vista 64bit did NOT start out very well with it and it took until just late last year for the problems to be sorted out (AFAIK).

The memory remap feature in most BIOS's is to allow the remapping of the overlapped PCI memory above the total physical memory and is designed to be used in 64bit systems. Many systems need this to be Enabled for the proper mapping of memory over 4G's.

Thanks for the enlightenment- as I went with OCZ ReaperX series of RAM, I was unable to go with the 8 GB I had originally planned, and once I learn my way through Overclocking, from what I have heard I will get better results having only 2 X 2 GB 'sticks' rather than 4 x 2 GB sticks anyway, for the C2Q 6600 that I have.

Of course, there is also the caveat that this is the first time I am actually running a 64bit OS in the first place - my previous machine was a dinky P4 3.2 GHz Prescott CPU based machine with 3 GB of DDR RAM and all IDE drives :P So it is not surprising that I was unaware of this little factoid.

NP John.
I was unaware of this lil problem in Vista until I went with 64bit and 4G's just late last summer. I immediately ran into problems with my TV tuner card and getting all the RAM to show and be available. The Remap feature allowed Vista to see and use all 4G's but I still had to remove a stick to get my TV tuner working again.
Hauppauge support said that Vista was what the problem was and that MS was having issues with Vista 64bit not handling the mapping of the memory properly and they were waiting fr MS to release a fix. Then a month later I got contacted by Hauppauge again to see if I wanted to test out a new beta Patch for the problem. Of course I did, I've beta tested s'ware for years so I jumped at it, and I haven't had a problem since then.

I remember when I first Googled this issue, I was totally flabbergasted at the amount of people on forums all over having the same problems with Vista 64bit OS and getting all their RAM to show in the system specs and be used properly. I bought 64bit for the same reason as everyone, and here I was reading about problem after problem with the way Vista x64 was handling the memory mapping...I thought for awhile that maybe going 64bit was a bad idea, but it's been smooth since then.
All I know is that for the proper handling of overlapped memory for PCI devices, the Remap feature has to be enabled for some BIOS's to handle this. It may be sorted out by now in newer boards but not mine...

Interesting. And it brings to light another problem I still have yet to figure out - but it may be related. I just recently (~3 weeks ago) built my new machine with the following specs:

• Core 2 Quad 6600 G0 rev.
• eVGA 780i motherboard
• OCZ PC2-8000 ReaperX HPC 4GB Edition (2 X 2GB) RAM
• eVGA 8800 GTS KO 512MB GA
• Dual 500 GB 32MB Cache Seagate Barracuda SATA II HDs
• WD 250 GB 8 MB Cache HD
• ThermalTake Armour Case - with 250 mm side fan

All the specs in my WEI are 5.9 *except* the RAM - it is at 5.4. And CPU-Z reports that the RAM is PC6400 not PC2 8000 like it should....so, I wonder if there is something I should be looking at in terms of getting the RAM to play much more nicely with Vista 64bit....

And this is without any over clocking....

Oh, and I also put a Hauppage WinTV PCI-e tuner card in - but I had no issues at all - works like a charm.

I have not heard of issues on XP x64 or Vista x64 about RAM over 4GB. I do know overclocking on any 64-bit is not as good as 32-bit OS.

I have three workstations with server boards running over 4GB. My Tyan Thunder K8W rev 3 is running 6GB and pair of AMD 265 dual core Opterons. My Tyan Thunder K8WE rev 4 is running 8GB and pair of AMD 280 dual core Opterons. My Supermicro X7DWA-N is running pair of Intel quad core E5430 Xeons with 16GB of RAM. The K8W can't see 8GB because the revision of the board does not support dual cores fully. I can't enable the memory hole on it. I can go back to single core Opterons to get 8GB. I rather have the four cores instead.

The problem is more likely how computer boards are setup. You don't want to overclock on your base OS install. You want to make sure the CMOS is configured properly to support your hardware.