Taking a brief respite from the Linux/iTouch project (mainly because I simply haven't had time to focus on it over the last couple of weeks) I decided to see if I could goose my mainbox a little to coax a bit of extra 'oomph' out of it.
It's a Shuttle box - one of the four I have, because I love these SFF barebones boxes with their dinky little chassis and tiny hi-spec mobo all prepped and waiting for someone to drop a CPU, memory and disk into them. In this case (hohoho) it's an SD32G2, which shipped with an Intel chipset motherboard into which I dropped a Core 2 Duo E6600 processor, 4GB DDR2 RAM, an IDE DVD-ROM, a 500GB SATA HDD, and an nVidia GF7600GT. All that runs off a 250W mini-PSU (just - I carefully selected components that wouldn't exceed the power output from the PSU even under load).
Note: I normally go for nVidia chipset mobos, but in this case there wasn't one that supported the C2D CPUs at the time (this is, what, 14 or 15 months ago). The Intel looked pretty good on paper, supported C2D, and was available at SFF - so I took a chance. Overall it's been entirely satisfactory, so the gamble paid off.
The graphics card is air-cooled and by far the loudest component - the Northbridge is air-cooled with a little 4000RPM silent fan, and the CPU air-cooled via Shuttle's excellent 'ICE' phase-transition cooling block, which is pretty much silent except under heavy load - at which point the variable-speed fan slowly winds up from about 800RPM to 1200RPM or so. And even then it's more of a barely-audible sigh than the kind of noise I used to get from my old CoolerMaster axial fan, which looked and sounded like a Phantom jet turbine.
Anyway, this has all been humming along nicely for about a year, and is capable of handling almost everything I throw at it without blinking. But there've been a couple of things I've been doing of late that have been stretching it a bit thin, like running two or more Linux VBox VMs at the same time as I have a video transcoder going (converting AVI to MP4 for the iTouch) whilst simultaneously ripping a DVD, playing MP3s, and surfing the net. It's not grinding to a halt, but it's noticably less snappy, and of course Vista with Aero switched on is an added overhead...
So I tend to have a three-year cycle on my PCs - I assemble them with a little future-proofing in mind, so that I can have 18 months on the 'stock' settings, and then when it starts feeling a little tired I can tweak things and run for another 18 months by pushing the envelope a bit. And that's where I am right now, just starting to notice a little age in the kit and digging-out the specs for the CPU, memory and GPU so I can have a fiddle.
The first thing to look at is the CPU clockspeed. I've done a fair bit of overclocking in the past, so this holds no fear for me - especially with modern motherboards and BIOSes. which just freeze the box at bootup if you go too far, and don't (or hardly ever, at least ;)) allow any lasting damage to occur at that point. A simple BIOS reset is all that's needed to get back to the stock settings, and you're back in business.
The best way to find your overclocking sweet spot (the fastest settings that give you a stable processor) is to increment things in small steps, noting your changes as you go along, and gradually building up until you can't go any further. Then drop back an increment, and you're done. The settings are held in the BIOS, and you're generally looking at the Front Side Bus (FSB) frequency, the clock multiplier, and the Vcore CPU voltage. More often than not these days the CPU will be multiplier-locked, meaning you can't change that particular setting, but you've still got the FSB and Vcore at your disposal.
The E6600 is multiplier-locked at x9, and has a stock FSB of 266MHz (which is where you get the rated 2.4GHz speed from - it's 9 x 266, which is 2394MHz, rounded up). The Phoenix BIOS on my mobo lets me vary the FSB from 200MHz up to 350MHz, which means theoretically I can get the CPU up to 3.15GHz. You might see quoted overclock speeds higher than this for some E6600s - I think there might be models out there now which can have their multipliers adjusted too, so of course if your mobo let you tweak the FSB to, say, 400MHz, and let the multiplier go up to x10, then you're looking at 4GHz right there.
But life's not that easy, because the natural overclock limits here are volts and heat. As you crank up the FSB, the CPU runs warmer. You might also need to tweak Vcore up as well to keep the chip stable at higher frequencies, and those extra volts will contribute to the heat increase too. And when a CPU gets too hot, you'll see instability and possibly permanent damage. So in practice, your overclock sweet spot is the point at which the FSB and Vcore balance to give you a stable CPU, and the heat from that new balance point is being effectively removed by your cooling facilities.
At 2.4GHz the E6600 runs idle at around an average of the mid-40s Celcius, and under load will probably never go above 55C. In my ICE-cooled rig, it idles at about 39C and peaks at about 51C. But even if my BIOS let me attempt to drive it at 4GHz, it'd be a disaster because at that level I'd need some much heavier-duty cooling (i.e. something like that old CoolerMaster turbine, or serious water-cooling, etc). Even with the theoretical maximum of 3.15GHz that the mobo will let me go to, I doubt the existing cooling will get me a stable CPU - but we'll see...
The basic mechanics of overclocking are:
1. Tweak the FSB up a bit in the BIOS
2. Reboot, and see if the machine starts and loads your OS
3. Check idle temperature
4. Run a stress test (e.g. Prime95) on all cores for at least 30 minutes
5. Keep watching the temperatures
If your FSB tweak doesn't boot, or your OS is flakey (e.g. bluescreens in Windows) you can try tweaking the Vcore up bit to give the CPU a little more juice, in case it's stalling at the higher frequency. Remember that Vcore increases will also push the core temperature(s) up, so even if you get a stable OS after a Vcore nudge, you might still be better to drop back to a lower FSB if the temperatures are high. I'm playing safe by using 60C as the peak cut-off point - if the temperature goes above that, I'll drop back. I've seen reports of E6600s running at 60C-70C idle, going to 80C under load. This is Not Good. Your preference may vary, of course, but I'd definitely be wary of an idle temperature above 50C, and a peak load temperature above 65C.
So last night I nudged the FSB up from 266MHz to 282Mhz, and got a rock-solid boot at 2.5GHz. Idle temperature in the cores was 39C, and Prime95 gave a peak of 54C. After an hour of stress-testing with no problems, I gave the FSB another little poke up to 300Mhz, and again got a solid 2.7GHz idling at 40C, peaking under load at 57C. By the time an hour had gone by it was getting late, so I decided to call it quits for the night.
Tonight we'll be going to an FSB frequency of 316MHz, which puts the E6600 at 2.8GHz, and we'll see where we go from there. Note that I haven't had to nudge Vcore yet, and I still have 3C headroom on my 'safe' peak load temperature. Also, I haven't tweaked my memory latency timings (they're still set via SPD at 5-5-5-15) so I might find I can improve the performance of the box a bit more if I can tune those a bit once I get to a maximum stable CPU configuration. And finally, I haven't done anything with RivaTune yet, which is where all the GPU frequencies are adjustable to overclock the graphics card.
My current Windows Experience Rating is 5.3, and it's the GPU that's the bottleneck on that. So once my CPU and memory are tweaked to their safe and stable limits, I'll hit the GPU and see if I can coax another WER point or two out of it. Maybe I'll be able to play Crysis at a decent framerate and detail level by the end of it all... :)
Later...
OK, back in front of the rig now, and I've just tweaked the FSB up to 316MHz. On the first reboot, Windows bluescreened before getting to the logon screen, so back to the BIOS I went and bumped Vcore up by 25mV. I also switched the ICE fan over to 'Low' instead of 'Smart', which made no audible difference but set the rotation to about 1900RPM. Reboot again, and now we're up and running. The E6600 is at 2.8GHz, the fan is steady at 1950RPM, it idles at about 40C and with Prime95 running on both cores it's peaking at 55C - a little lower than yesterday, but that's because I've preset the ICE fan now.
I then tried going to an FSB of 324MHz, but without tweaking Vcore again it wouldn't get past the POST screen. So I twiddled Vcore up in 25mV increments until I got to 100mV (so my Vcore is now at 1.4V instead of the stock 1.3V) and then ... something odd happened. I got past the POST screen, but the machine reported a 'Non-system disk' error and stopped. Looking at the BIOS, I can see that pushing the Vcore up appears to make the machine 'forget' how to use the SATA controller, as it shows no drive attached, and if I make it search for one, it doesn't find it.
After a BIOS reset, the SATA drive re-appears, and all is well. So I'm going to have to have a play with it, but it looks like 316MHz might be the limit. Which is fine - we started at 2.4GHz and have a stable system at 2.8GHz, so I can live with that. Still, it'd be nice to get to 2.9GHz or even the big three-point-oh... ;)
It's a Shuttle box - one of the four I have, because I love these SFF barebones boxes with their dinky little chassis and tiny hi-spec mobo all prepped and waiting for someone to drop a CPU, memory and disk into them. In this case (hohoho) it's an SD32G2, which shipped with an Intel chipset motherboard into which I dropped a Core 2 Duo E6600 processor, 4GB DDR2 RAM, an IDE DVD-ROM, a 500GB SATA HDD, and an nVidia GF7600GT. All that runs off a 250W mini-PSU (just - I carefully selected components that wouldn't exceed the power output from the PSU even under load).
Note: I normally go for nVidia chipset mobos, but in this case there wasn't one that supported the C2D CPUs at the time (this is, what, 14 or 15 months ago). The Intel looked pretty good on paper, supported C2D, and was available at SFF - so I took a chance. Overall it's been entirely satisfactory, so the gamble paid off.
The graphics card is air-cooled and by far the loudest component - the Northbridge is air-cooled with a little 4000RPM silent fan, and the CPU air-cooled via Shuttle's excellent 'ICE' phase-transition cooling block, which is pretty much silent except under heavy load - at which point the variable-speed fan slowly winds up from about 800RPM to 1200RPM or so. And even then it's more of a barely-audible sigh than the kind of noise I used to get from my old CoolerMaster axial fan, which looked and sounded like a Phantom jet turbine.
Anyway, this has all been humming along nicely for about a year, and is capable of handling almost everything I throw at it without blinking. But there've been a couple of things I've been doing of late that have been stretching it a bit thin, like running two or more Linux VBox VMs at the same time as I have a video transcoder going (converting AVI to MP4 for the iTouch) whilst simultaneously ripping a DVD, playing MP3s, and surfing the net. It's not grinding to a halt, but it's noticably less snappy, and of course Vista with Aero switched on is an added overhead...
So I tend to have a three-year cycle on my PCs - I assemble them with a little future-proofing in mind, so that I can have 18 months on the 'stock' settings, and then when it starts feeling a little tired I can tweak things and run for another 18 months by pushing the envelope a bit. And that's where I am right now, just starting to notice a little age in the kit and digging-out the specs for the CPU, memory and GPU so I can have a fiddle.
The first thing to look at is the CPU clockspeed. I've done a fair bit of overclocking in the past, so this holds no fear for me - especially with modern motherboards and BIOSes. which just freeze the box at bootup if you go too far, and don't (or hardly ever, at least ;)) allow any lasting damage to occur at that point. A simple BIOS reset is all that's needed to get back to the stock settings, and you're back in business.
The best way to find your overclocking sweet spot (the fastest settings that give you a stable processor) is to increment things in small steps, noting your changes as you go along, and gradually building up until you can't go any further. Then drop back an increment, and you're done. The settings are held in the BIOS, and you're generally looking at the Front Side Bus (FSB) frequency, the clock multiplier, and the Vcore CPU voltage. More often than not these days the CPU will be multiplier-locked, meaning you can't change that particular setting, but you've still got the FSB and Vcore at your disposal.
The E6600 is multiplier-locked at x9, and has a stock FSB of 266MHz (which is where you get the rated 2.4GHz speed from - it's 9 x 266, which is 2394MHz, rounded up). The Phoenix BIOS on my mobo lets me vary the FSB from 200MHz up to 350MHz, which means theoretically I can get the CPU up to 3.15GHz. You might see quoted overclock speeds higher than this for some E6600s - I think there might be models out there now which can have their multipliers adjusted too, so of course if your mobo let you tweak the FSB to, say, 400MHz, and let the multiplier go up to x10, then you're looking at 4GHz right there.
But life's not that easy, because the natural overclock limits here are volts and heat. As you crank up the FSB, the CPU runs warmer. You might also need to tweak Vcore up as well to keep the chip stable at higher frequencies, and those extra volts will contribute to the heat increase too. And when a CPU gets too hot, you'll see instability and possibly permanent damage. So in practice, your overclock sweet spot is the point at which the FSB and Vcore balance to give you a stable CPU, and the heat from that new balance point is being effectively removed by your cooling facilities.
At 2.4GHz the E6600 runs idle at around an average of the mid-40s Celcius, and under load will probably never go above 55C. In my ICE-cooled rig, it idles at about 39C and peaks at about 51C. But even if my BIOS let me attempt to drive it at 4GHz, it'd be a disaster because at that level I'd need some much heavier-duty cooling (i.e. something like that old CoolerMaster turbine, or serious water-cooling, etc). Even with the theoretical maximum of 3.15GHz that the mobo will let me go to, I doubt the existing cooling will get me a stable CPU - but we'll see...
The basic mechanics of overclocking are:
1. Tweak the FSB up a bit in the BIOS
2. Reboot, and see if the machine starts and loads your OS
3. Check idle temperature
4. Run a stress test (e.g. Prime95) on all cores for at least 30 minutes
5. Keep watching the temperatures
If your FSB tweak doesn't boot, or your OS is flakey (e.g. bluescreens in Windows) you can try tweaking the Vcore up bit to give the CPU a little more juice, in case it's stalling at the higher frequency. Remember that Vcore increases will also push the core temperature(s) up, so even if you get a stable OS after a Vcore nudge, you might still be better to drop back to a lower FSB if the temperatures are high. I'm playing safe by using 60C as the peak cut-off point - if the temperature goes above that, I'll drop back. I've seen reports of E6600s running at 60C-70C idle, going to 80C under load. This is Not Good. Your preference may vary, of course, but I'd definitely be wary of an idle temperature above 50C, and a peak load temperature above 65C.
So last night I nudged the FSB up from 266MHz to 282Mhz, and got a rock-solid boot at 2.5GHz. Idle temperature in the cores was 39C, and Prime95 gave a peak of 54C. After an hour of stress-testing with no problems, I gave the FSB another little poke up to 300Mhz, and again got a solid 2.7GHz idling at 40C, peaking under load at 57C. By the time an hour had gone by it was getting late, so I decided to call it quits for the night.
Tonight we'll be going to an FSB frequency of 316MHz, which puts the E6600 at 2.8GHz, and we'll see where we go from there. Note that I haven't had to nudge Vcore yet, and I still have 3C headroom on my 'safe' peak load temperature. Also, I haven't tweaked my memory latency timings (they're still set via SPD at 5-5-5-15) so I might find I can improve the performance of the box a bit more if I can tune those a bit once I get to a maximum stable CPU configuration. And finally, I haven't done anything with RivaTune yet, which is where all the GPU frequencies are adjustable to overclock the graphics card.
My current Windows Experience Rating is 5.3, and it's the GPU that's the bottleneck on that. So once my CPU and memory are tweaked to their safe and stable limits, I'll hit the GPU and see if I can coax another WER point or two out of it. Maybe I'll be able to play Crysis at a decent framerate and detail level by the end of it all... :)
Later...
OK, back in front of the rig now, and I've just tweaked the FSB up to 316MHz. On the first reboot, Windows bluescreened before getting to the logon screen, so back to the BIOS I went and bumped Vcore up by 25mV. I also switched the ICE fan over to 'Low' instead of 'Smart', which made no audible difference but set the rotation to about 1900RPM. Reboot again, and now we're up and running. The E6600 is at 2.8GHz, the fan is steady at 1950RPM, it idles at about 40C and with Prime95 running on both cores it's peaking at 55C - a little lower than yesterday, but that's because I've preset the ICE fan now.
I then tried going to an FSB of 324MHz, but without tweaking Vcore again it wouldn't get past the POST screen. So I twiddled Vcore up in 25mV increments until I got to 100mV (so my Vcore is now at 1.4V instead of the stock 1.3V) and then ... something odd happened. I got past the POST screen, but the machine reported a 'Non-system disk' error and stopped. Looking at the BIOS, I can see that pushing the Vcore up appears to make the machine 'forget' how to use the SATA controller, as it shows no drive attached, and if I make it search for one, it doesn't find it.
After a BIOS reset, the SATA drive re-appears, and all is well. So I'm going to have to have a play with it, but it looks like 316MHz might be the limit. Which is fine - we started at 2.4GHz and have a stable system at 2.8GHz, so I can live with that. Still, it'd be nice to get to 2.9GHz or even the big three-point-oh... ;)
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