The video card I managed to buy for the tests is none other than the GTX 285 1gb! Is the last and most powerful DIRECTX 10 GPU. It is very weak for DirectX10, however for DirectX9 and Windows XP it provides the best performance possible!
1. GTX 285
2. long jumper caps present on all socket 754&939 Abit boards

Congrats on that card, looks great. GTX 285 are becoming rare these days in local market. I would highly recommend them for s939. They have better compatibility with dx8 than later cards and sufficient performance for best graphics in Windows XP dx9 games.

GeForce GTX 480/580 are best for Windows Vista dx10 games and GTX 680/780 best for Windows 7 era dx11 games.

GTX 285 allows to reconfigure FAN profile in BIOS in nibitor, which can be flashed so no need for MSI afterburner. The card no longer has to work at 80'C.

GTX 280/285 are nice. I was comparing a 280 to a special edition 950MHz 4890 a few years ago and the Nvidia card runs some games so much better. I think Dishonored runs around twice as fast. Maybe much better driver support for Unreal Engine 3. I think as usual Nvidia kept working on the drivers years after ATI/AMD had moved on.

Because GTX 285 is such a powerful card we need a CPU to match it. The best CPU for socket 939 is FX-60 however that processor is very rare and incredible expensive as it is a collector item. I do not have it. However I got the next best thing: Athlon 64 X2 4800 running only 200 MHZ below the famed FX-60. This will bottleneck the video card but it is better to have a GPU that can run all tests at 1600*1200 with ease that to have a card that limits performance at such high resolution.
Nforce4 accepts SSD's without problems so I used a Kingston 240gb one; for the storage tests I installed a 150gb WD raptor in the system; some SATA optical drive also work just fine.
I use an arctic cooling freezer 7 pro and despite the fact that the CPU has a TDP of 110W it proved incredible easy to cool - with C'n'Q disabled and running prime 95 it never exceeded 50C! So my early beliefs that all processors with > 100W TDP represent a problem as far as cooling goes proved unfounded!

And here is the "sound card" used: audiomax provided with socket 939 nforce4 boards and the audiomax provided with socket AM2 boards; the nforce4 contains a simple AC97 codec while nforce5 has the HDA under the form of realtek 882 chip - roughly equivalent to a creative live from 1998 or nvidia sound storm from 2001:

And here is the system full assembled: Athlon 4800 with arctic freezer 7, 4gb RAM, Abit an8 ultra; GTX 285; SATA SSD 480GB; DVD; WD 150gb; Corsair TX850M PSU; cooler master case.

The bios of an8 ultra has the best monitoring options of any socket 939 board; the Corsair ram I used works only at 2.6V so auto voltages selected across the board:

All 6 fans are monitored and can be set according to multiple temperature points and different voltages:

Not even DFI has that kind of monitoring parameters!
The rest of the BIOS is pretty common with some exceptions that I will explain below. The advanced chipset menu contains the DRAM configuration page. Corsair 3500LL pro automatically uses pretty good memory timings if set to SPD:

The integrated peripherals menu has some of these exotic options that are specific to nforce4 chipsets:
1. USB park mode disables USB ports when not in use; it is of no consequence where you are using USB sticks, however if you are using an USB mouse it leads to jerky movements therefore it should be disabled.
2. USB TD reads adjusts the priority of USB transfers.
3. USB periodic data reads: USB ports are polled continuously for any data to be transferred to/from USB device or at a set interval.
4. USB asynchronous data reads: to my understanding these option controls how data over USB ports is actually transferred.

USB memory type in the USB controller options page should always be set to SHADOW unless you want to boot into DOS from a USB stick which is possible on Abit AN8 ultra.
In general you should not mess with the USB settings in the BIOS and leave them at their default settings!

Everything not needed such as floppy controller, firewire, IDE ports is disabled in order to maximize performance.

Also unique to Abit is the black box that shows you how many hours the system has been running, how many times you pressed the RESET button and other info. It remembers these values even if you remove the CR2032 battery. Also you can save up to 5 presets with specific BIOS setups - for example for an overclocked Athlon 64 3500 or for a specific fan configuration.
Pictures ASAP.

The system up and running - to my surprise the temperatures are very good and never exceed 50C for the CPU and 40C for the board even when running multiple SUPERPI instances!

Looks s3xy, Corsair Pro is a nice touch.

Thank you.
As promised here are the pictures with the board black box - I never seen something similar on any other board, it shows how much the system was turned on, number of hours the board was connected to the electrical outlet and so on . Also you can save up to 5 presets with different settings:

And here are the system details; the GTX 285 remains pretty cool, even running Company of heroes at max settings it does not exceed 70C!

The only problem remaining is the command rate: searching for a solution... to get a stable system with CR 1T .

With UDIMMs I think that you will have to make a small compromise and use max 3GB RAM (double rank + single rank) for a chance to run in CR 1T mode or make a big compromise and have 2GB RAM only where CR 1T will work for sure. CR 2T will diminish advantages X2 s939 CPU would enjoy over s754.