P5Q - Bother with PC8500 RAM or stick with PC6400

Hello!

As part of a new upgrade cycle for my recording studio I settled on the new ASUS P5Q (not deluxe, not-E, not Pro) - just the plain ole P5Q.

This rig will be running Vista 64 with a Q9450 Quad core and will probably get 8GB of RAM sooner than later but I purchased Corsair TWIN2X4096-8500C5DF (4GB in a 2x2GB set) to get started.

Got the board, the RAM, the Q9450 processor and got to it. The build went very fast. However - at first start up - nothing. Board powers up, lights flash, IDE lights give a little flash...fans are up...looks normal inside - no so good on screen. After ruling out some sort of "suspend" mode or anything else out of the ordinary...I flashed the BIOS to version 703 - which apparently enables the P5Q to work with "additional memory types" - thought I might get lucky. No go. No nothing.

Long story short - I pulled the (2GBx2) TWIN2X4096-8500C5DF in favor of a (4x1GB) set of TWIN2X4096-6400C5DHX instead. The box came up no problem and I was able to install Vista and some apps.

Spend all of Monday researching the "no POST" problems and finally solved the issue by changing the 4 pin ATX connector to the 8 pin ATX connector and it fired up no problem. Was able to hit the BIOS and basically set everything to Auto. But...when Vista goes to load - instant Blue Screen. With various error messages. From Bad_POOL_HEADER to everything in between. I did read up on the limitless posts both here and other forums regarding the "old" circa Nov 2007 issue of Vista issuing a Blue Screen with 4GB of RAM installed - but that was fixed with Service Pack 1 (which is baked into my DVD media). Plus - when I use 4GB of TWIN2X4096-6400C5DHX - there is no problem at all.

Here on Tuesday - I am getting of mixed info on what to try when I get home to try and get this board working soundly with the PC8500 - but then I started thinking about this a bit more.

I am planning on 8GB for this rig anyway - and I have no interest in overclocking anything (Just stability - since this workstation basically is responsible for the core operations of my business) - would it be a more prudent step to just forgo the ongoing blue screens and hassles of trying to get the 1066 8500C5D working and settle into a nice comfy set of of 4x2GB TWIN2X4096-6400C5DHX instead?

I have also read horror stories about installing memory in all four slots and then having to downstep the memory frequency back to 800mhz if I do decide to try and install 8GB of the PC8500 RAM.

If I have to step back from 1066 to 800 - I may as well just get 8GB of TWIN2X4096-6400C5DHX - that I have already confirmed works fine with all 4 slots populated at 800mhz?

Is there a real tangible difference between PC8500 and PC6400. I have read that memory branded as PC8500 is simply overclocked PC6400

Appreciate any comments!

Cheers!

VP