I'm building a rig which would serve primarily as HTPC with occassional gaming and photoshop use.
I will be overclocking the CPU and narrowed down my choices to i5 750(1156) and i7 920(1366). Heat and low-load power consumption is important factor to consider.
1. In terms of power consumption and heat: i5 overclocked by increasing the stock voltage = i7 920 overclocked at stock voltage??
If there is a difference, how big is that. I'm most concerned about the idle/low load power consumption.
2. Is it possible to overclock i5 750 with Turbo on?
1) not sure, I haven't heard of any huge differences.
2) yes but the resulting maximum clock may be lower than doing it the old way (turbo isn't ultra configurable, so when you change the base it may become unstable) and you should also remember 'turbo' only engages with single core applications and is only applied to a SINGLE core. Overclocking manually causes all four cores to run at the higher frequency (and results in a much faster result)
If you're going to overclock, don't bother with the turbo. It's brilliant for stock or mild overclocks on mainstream machines, but when you're overclocking it'll just get in the way once the speed gets higher.
For idle etc I just make sure I have Intel SpeedStep etc enabled, this auto underclocks your CPU when its not needed by dropping the multiplier. This is usually on by default.
I have heard that the i5 750 requires less voltage than the i7 920 for higher overclocks and lower voltages mean lower temperatures.
I can't confirm since I do not own a 920 but these are my results.
I own a 750 running 3.8ghz with 1.26v 100% stable. Easily hit 4.2ghz on it, but load temps were approaching 70c so I just decided to keep it conservative for longer life. I'm using the cheap 212+ hyper heatsink also. (59c @100% load)