30+6mm M3 standoffs:
[url]http://www.amazon.com/100pcs-Female-Fixed-Standoff-Spacer/dp/B01071VHDU?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00[/url]

35+6mm standoffs:
[url]http://www.amazon.com/100Pcs-Brass-Standoff-Spacer-Pillar/dp/B00X7BVKOE?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00[/url]

Total distance between boards -- 65mm.

more spacers:
[url]http://www.newegg.com/Product/Product.aspx?Item=9SIA67038S9273[/url]
[url]http://www.newegg.com/Product/Product.aspx?Item=9SIA67038S9287[/url]

power switches:
[url]http://www.ebay.com/itm/301694042052?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT[/url]

12V plugs:
[url]http://www.ebay.com/itm/262321746827?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT[/url]

32GB USB sticks:
[url]http://aaawave.com/p-29611-mushkin-mknufdam32gb-atom-series-usb-30-32gb-flash-drive.aspx[/url]

cheap memory, cpu, mobo:
[url]http://www.newegg.com/Product/Product.aspx?Item=N82E16820231962[/url]
[url]http://www.newegg.com/Product/Product.aspx?Item=N82E16819117563[/url]
[url]http://www.newegg.com/Product/Product.aspx?Item=N82E16813157678[/url]

efficient psu:
[url]http://www.newegg.com/Product/Product.aspx?Item=N82E16817438055[/url]

picopsu:
[url]http://www.mini-box.com/picoPSU-90[/url]

Or you could try the 80W version, but the 4A limit on 12V scared me:
[url]http://www.mini-box.com/picoPSU-80[/url]
plus a P4 cable: [url]http://www.mini-box.com/4-Pin-P4-Mini-Power-Cable[/url]

I already recycled an old case, case fans, and network switch. I already owned the tools and supplies to make custom length ethernet cables.

Several items above are in largish quantity as my current plan is build one of these beasts each year.

i5-6400T timings (post 1 of 3)
 

There was some discussion about the T versions of skylake.
Here are some benchmark results

i5-6400T uses 45 W when running stress test and cost $150 from Amazon.

Intel(R) Core(TM) i5-6400T CPU @ 2.20GHz
CPU speed: 2346.43 MHz, 4 cores
CPU features: Prefetch, SSE, SSE2, SSE4, AVX, AVX2, FMA
L1 cache size: 32 KB
L2 cache size: 256 KB, L3 cache size: 6 MB
L1 cache line size: 64 bytes
L2 cache line size: 64 bytes
TLBS: 64
Prime95 64-bit version 28.7, RdtscTiming=1
Best time for 4096K FFT length: 21.482 ms., avg: 21.520 ms.
Timing FFTs using 2 threads.
Best time for 4096K FFT length: 11.201 ms., avg: 11.228 ms.
Timing FFTs using 3 threads.
Best time for 4096K FFT length: 8.011 ms., avg: 8.078 ms.
Timing FFTs using 4 threads.
Best time for 4096K FFT length: 6.935 ms., avg: 7.014 ms.

Timings for 4096K FFT length (1 cpu, 1 worker): 19.31 ms. Throughput: 51.79 iter/sec.
Timings for 4096K FFT length (2 cpus, 2 workers): 20.51, 20.51 ms. Throughput: 97.50 iter/sec.
Timings for 4096K FFT length (3 cpus, 3 workers): 23.46, 23.66, 23.46 ms. Throughput: 127.51 iter/sec.
Timings for 4096K FFT length (4 cpus, 4 workers): 27.27, 27.15, 27.18, 27.42 ms. Throughput: 146.75 iter/sec.

i5-6600T timings (post 2 of 3)
 

i5-6600T uses 57 Watts when running mprime stress test and cost $226 from nextwarehouse.com

All 3 postings use the ASrock H110-ITX MB with DDR4-2400 RAM.

Intel(R) Core(TM) i5-6600T CPU @ 2.70GHz
CPU speed: 3096.83 MHz, 4 cores
CPU features: Prefetch, SSE, SSE2, SSE4, AVX, AVX2, FMA
L1 cache size: 32 KB
L2 cache size: 256 KB, L3 cache size: 6 MB
L1 cache line size: 64 bytes
L2 cache line size: 64 bytes
TLBS: 64
Prime95 64-bit version 28.7, RdtscTiming=1
Best time for 4096K FFT length: 16.418 ms., avg: 16.446 ms.
Timing FFTs using 2 threads.
Best time for 4096K FFT length: 8.764 ms., avg: 8.835 ms.
Timing FFTs using 3 threads.
Best time for 4096K FFT length: 6.902 ms., avg: 7.041 ms.
Timing FFTs using 4 threads.
Best time for 4096K FFT length: 6.494 ms., avg: 6.572 ms.

Timings for 4096K FFT length (1 cpu, 1 worker): 15.60 ms. Throughput: 64.09 iter/sec.
Timings for 4096K FFT length (2 cpus, 2 workers): 17.06, 17.06 ms. Throughput: 117.23 iter/sec.
Timings for 4096K FFT length (3 cpus, 3 workers): 20.77, 20.79, 20.76 ms. Throughput: 144.42 iter/sec.
Timings for 4096K FFT length (4 cpus, 4 workers): 25.82, 25.82, 25.77, 25.79 ms. Throughput: 155.04 iter/sec.

i5-6500 timing (post 3 of 3)
 

Included for calibrating my results with other peoples results.

I5-6500 uses 67 Watts when running mprime stress and cost $180 from Microcenter

None of the 3 tests had BIOS voltage changes.

Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz
CPU speed: 3097.33 MHz, 4 cores
CPU features: Prefetch, SSE, SSE2, SSE4, AVX, AVX2, FMA
L1 cache size: 32 KB
L2 cache size: 256 KB, L3 cache size: 6 MB
L1 cache line size: 64 bytes
L2 cache line size: 64 bytes
TLBS: 64
Prime95 64-bit version 28.7, RdtscTiming=1

Best time for 4096K FFT length: 16.487 ms., avg: 16.512 ms.
Timing FFTs using 2 threads.
Best time for 4096K FFT length: 8.736 ms., avg: 8.803 ms.
Timing FFTs using 3 threads.
Best time for 4096K FFT length: 6.812 ms., avg: 6.900 ms.
Timing FFTs using 4 threads.
Best time for 4096K FFT length: 6.384 ms., avg: 6.453 ms.

Timings for 4096K FFT length (1 cpu, 1 worker): 15.21 ms. Throughput: 65.73 iter/sec.
Timings for 4096K FFT length (2 cpus, 2 workers): 16.41, 16.43 ms. Throughput: 121.79 iter/sec.
Timings for 4096K FFT length (3 cpus, 3 workers): 19.89, 19.98, 19.92 ms. Throughput: 150.54 iter/sec.
Timings for 4096K FFT length (4 cpus, 4 workers): 25.30, 25.31, 25.27, 25.16 ms. Throughput: 158.36 iter/sec.

Latest picture ? :smile:

Thanks for those benchmarks!

[QUOTE=ramshanker;431960]Latest picture ? :smile:[/QUOTE]

In a week when CPUs 6 and 7 are in place.

Ugh.

CPUs #6 and #7 are up and running. That's great. But, I happened to run a throughput benchmark on CPU #5 and it is 10% slower than all the others. I've run pmbw and it is definitely a memory bandwidth problem, i7z reports the CPU speed is the expected 3.3 GHz. Surprisingly, I swapped the DDR4 sticks with another CPU and the problem remains. So the problem is either in the motherboard or CPU. CPU #5 is on the bottom of the stack, so now I have to disassemble the entire stack and swap the CPU to isolate the cause.

Moral of the story, if you embark on a similar project test the throughput of every unit before putting it all together.

Swapped the CPU - still slow. For grins, swapped the PicoPSU -- still slow.

So it seems we have a defective motherboard. I'll check for a BIOS before beginning the RMA process.

[QUOTE=Prime95;432446]
So it seems we have a defective motherboard. I'll check for a BIOS before beginning the RMA process.[/QUOTE]

Might check the CPU temp.
When they get too hot they reduce the clock to cool themselves.

[QUOTE=bgbeuning;432496]Might check the CPU temp.
When they get too hot they reduce the clock to cool themselves.[/QUOTE]

temps in 50s, i7z says it is running at 3.3 GHz.