Well I finally dug into my junk pile and started a Throttlestop project of my own.
I fired up a Dell XPS 420 (LGA775, BTX, DDR2, X38). I just wanted to test some DDR2 4GB modules to see if they were low density. But when they were compatable things started to happen.
QX9650, 12GB DDR2 800, GTX1060 6GB. Alphacool skived copper heatsinks on the VRM MOSFETs. I tried an XPS 720 CPU cooler but it wasn't up to the task, so I installed my custom made 150x50mm Delta (259cfm) fan conversion using that heatpipe (8mm pipes) cooler. Problem solved.
I played with SetFSB and got up to 374MHz, then applied Throttlestop and got to 4.3GHz. No stability there to speak of. But I'll get back to that later.
With Just TS 12.5x333=4.15GHz which is the "normal" overclock for X38 BTX computers. There are few of them at userbenchmark in the Dell T3400 lists.
What I really need to do is start over with a pinmod to 400fsb and nail down 10.5x400fsb for 4.2GHz.
That would give a nice base clock of 9.0x400=3.6GHz (nice step up from my existing Optiplex 380 Xeon 3.33Ghz).
A couple of options in the 4-4.2Ghz range, either SetFSB, or TS.
And the nuclear option of editing TS to overclock just 2 cores and try for something in the 4.3-4.4Ghz range.
I was planning on saving the XPS 420 for last after testing on a T3400. But it was laready running, and so I used it to test the 4GB DDR2 modules I had. It's much nicer looking computer than the T 3400 or XPS 410. And this one was owned by a little old lady and only driven on Sundays. It has a 2ndary USB based display on it that can show Temp. Voltage, and clock speed info. I've heard it can be made to work in Win7.
So far I've just run this in the car porch with no internet, and 90*F. Florida weather. Just an OS and some tuning apps. loaded.
I'm using the Dell 425W PSU from a T3400. This gets the wiring length right for a BTX Mid tower, and 3x18A rails available.
It has 2x 6 pin PCIe cables vs. the single one the 2 rail 375W it came with had.