I gathered four LGA775 mobo's - 3 from Craigslist and 1 from eBay. I
also gathered a few CPU's from my local PC recycler (RE-PC in Seattle)
and eBay. All of these parts are dirt cheap so I won't be heartbroken if
they die.
For my GPU I pulled my 3080 out of my daily gaming rig. So I set out to
get world records with the oldest CPUs that would run Windows 10 and a
modern GPU.
My first rig was an Intel confidential / engineering sample QX6700. I
put this under a modern Zalmann cooler - one of the only ones I could
find with LGA775. For some reason this CPU would not go above 3.2ghz. I
am pretty sure it was the CPU and not the mobo - no matter what FSB or
multiplier I gave it, it wouldn't top 3.2ghz.
I paired this with 8gb of DDR2-800 ram and hilariously, an NVMe drive on the other PCIe slot.
I got a TimeSpy overall score of 4661. The graphics scores were fine but
the CPU scores were understandably abysmal. But this is the world
record for the combination of QX6700 + RTX 3080 - because nobody has
submitted benchmarks for this combo.
dylanrush`s 3DMark - Time Spy score: 4661 marks with a GeForce RTX 3080 (320bit)
At almost 20 years old, the QX6700 was very snappy, especially with a modern SSD. I really think it would perform fine for a person just doing office work and internet browsing.
The Pentium D 805 was my first real overclocking chip. Unfortunately I
couldn't get this to properly boot into Windows 10. So I put it away for
another day. I also had a Pentium D 945. As far as I know, this is the
oldest chip that will possibly boot into Windows 10.
I put this chip between a ASUS P5W Deluxe (Intel 975X chipset) and a new
Raidmax 240mm AIO cooler. The GPU was again my 3080. This time around I
procured some 1066mhz DDR2 RAM from Corsair.
With voltages in the rather extreme range (1.65v CPU, I think 1.7v FSB
and 1.5v NB), I was able to get the CPU up to 4.9 ghz (!), stable enough
to run a benchmark.
Time Spy didn't run on this chip - probably lacking some instructions.
Fire Strike did, though. I have the lowest Fire Strike benchmark ever submitted for a 3080. But again I have the world record, this time for
the combination of Pentium D 945 + RTX 3080. I truly think I may be the
first person to ever combine this CPU and GPU. I also might be running
the fastest Pentium D in the world right now.
