Sunday, December 07, 2014

PC Update: Final piece of the puzzle

Over-clocking the Ageing CPU was the final stage required to bring my ageing gaming rig up to 2015 specification.

Original post here:

Earlier trials had proven my i5-760 had plenty of over-clocking headroom while maintaining stability but that the stock Intel heat-sink was unable to dissipate the additional heat generated. A Zalman CPS10X  heatsink addressed that problem for a modest €26 additional investment.

Zero points for neat cabling but at least the airways are clear. 

I had taken  measurements well and fitting the large heatsink posed no real problems although it took a while because I had to remove the motherboard to fit a rear retaining plate. The i5-760 has a factory locked multiplier so over-clocking is a trade-off that requires adjustments to cpu, ram and IMC voltages and timings. I used the utilities that came with my ASUS motherboard to get a ballpark position before manually tweaking. In the end I settled for a rock solid 25% over-clock that keeps the peak CPU temperature below 79°C under severe torture testing and to the mid 60's during actual heavy gaming. My i5 now runs at a nominal 3.6GHz but this isn't directly comparable to a modern 3.6GHz processor because of the older architecture. Nevertheless it should serve me well enough for the next year's gaming. 3D Mark Fire-strike score for the final rig is 8,717 which is less than 5% below their modern "High End Gaming PC" benchmark. The rig runs Assassin's Creed Unity smoothly as butter in high quality mode with Vsync at 60 frames per second. I got the game free with my GTX 970 graphics card and it looks absolutely gorgeous. It is probably the most beautiful game I have ever seen.

An interesting side story: Modern CPUs vary their internal clock rate and disable cores depending on temperature and load. In order to test over-clocking it is normal  to disable these energy saving features while doing stability and thermal testing. Once I determined that my CPU ran stably  within acceptable temperature limits at 3.6GHz.  I went back into the bios to re-enable these  features in order to avail of the energy saving benefits. On rebooting I was quite surprised to see that the processor was now running at 4.1 GHz rather than 3.6GHz??? It seems that my efforts had also enabled turbo mode which over-clocks the processor when less than half of the four cores are in use. I was worried that this would invalidate my careful stability tests but further torture testing didn't show up any glitches and I decided to leave it as is.

Here for reference is a full list of the before and after in my project to bring a five year old gaming PC up to 2015 standard with a budget of only €400.

Cost of Upgrade
2.9GHz /3.3GHz
I5-760 3.6GHz/4.1GHz
€26 for new Heatsink
4Gb  x 1333MHz
8Gb x 1666MHz
€25 for extra 4Gb
64Gb SSD Cache drive
€39 for SSD
€24 for Software
Graphics Card
Radeon HD 5850
Nvidia GTX 970
Total Cost of parts


Note 1: Total shipping costs came to another €18 for a total delivered cost of €442
Note 2: For an estimate of US equivalent prices just take the euro figures as US $. Our high sales tax pretty much cancels out the euro dollar exchange rate.

A little over my €400 budget but I should recoup the difference by selling my HD 5850 and the bulk of the investment will still be useful in a new build next year. The GTX 970 should be good for two years at least. I intend to keep using the SSD cache as long as I still use large spinning HDDs. Even the heatsink may be useful on a new motherboard. Only the ram is almost certain to be obsolete.

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