E6750 vs E8400 power consumption comparison

[amyhughes]

I just swapped out a modestly over-clocked E6750 (3.0 GHz 375x8, 1.325V) for an E8400 clocked the same (3.0 GHz 375x8, 1.05V). Lower voltage, same clock (note non-standard), but no idle power savings. Processor load power dropped 21W, though. I also did some graphics tests and found 12-14W improvement.

idle at windows desktop: 105W -> 105W (both throttled to 2.25 GHz)
prime95 max-power torture: 158W -> 137W
gaming, low polygon, high framerate: 144W -> 130W
gaming, high polygon, low framerate: 137W -> 125W
brief power-on spike: 158W -> 142W
off/standby: 6W -> 6W

The closest I do to gaming is Second Life, so that's where those numbers came from. It's an environment where content comes from players, so it isn't optimized like most games. There is high polygon count and way too many large textures.

Here's the system:

Ninja rev B, fanless
Gigabyte GA-P35-DS3L
G.Skill 4GB (2 x 2GB) DDR2 800
MSI nVidia 8600GT 512M, fanless
WD 160 GB HDD
Gigabyte i-RAM w/ 4 x 0.5G DDR 400
M-Audio Audiophile 24/96
Samsung DL DVD burner
Antec Sonata, tricool 120mm, 380W PSU (old)
the Ninja's 120mm Scythe fan intake
WinXP Pro

Next comparison: old Antec 380W vs Sparkle 250W 80+

[Modo]

Have you tried undervolting the CPUs? The E6xxx series seems to work fine at stock speeds with the voltage dropped by some 20%. It would be good to see how the E8xxx series compares in that area.

[amyhughes]

The 8400 is undervolted. At 1.0V it failed prime95 after a few minutes. Ran 1.05V for a couple hours, so that's what I'm sticking with. The 6750 is near stock voltage, but only because it's over-clocked. I had less luck undervolting that one than others did.

[smilingcrow]

I just swapped out a modestly over-clocked E6750 (3.0 GHz 375x8, 1.325V) for an E8400 clocked the same (3.0 GHz 375x8, 1.05V). Lower voltage, same clock (note non-standard), but no idle power savings.

idle at windows desktop: 105W -> 105W (both throttled to 2.25 GHz)

That is surprising as from the reviews I’ve read the 45nm dual cores use less power at idle than the latest 65nm versions at stock voltages. I can’t see why your configuration would be any different. Were the voltages at idle the same as given above?

[amyhughes]

Were the voltages at idle the same as given above?

6750 was at 1.325V and 8400 was at 1.05V, set in BIOS. I expected to see a difference at idle but didn't.