Sunday, May 29, 2011

Which Was Better?

I've had pretty good experiences with the three processors I purchased: the AMD PII X3 720 Black Edition, the AMD PII X4 965 Black Edition, and the Intel i5 750. I also had good experiences with the three graphic cards I purchased: an ATI HD 4650, and two ATI HD 5770's. I liked the three cases and the three power supplies.
I would have no trouble recommending any of these. I have confirmed that you cannot get extreme overclocks from any of them (although perhaps you could with more exotic cooling). And, I've confirmed that you can get modest overclocks even in a tight case if you use a better CPU HSF and replace the stock rear case fan with a higher volume unit like the Scythe. Specifically, the Intel i5 750 doesn't seem to throw anymore heat than the X4 965 and both run cool with upgraded HSF's. Using a case with good ventilation (like my two Cooler Master cases with 200 mm fans) you can get a bit higher. However, in all fairness, you can get more heat dumped off a high end graphics card than you can off either of these processors. This is why I chose HD 5770's with external exhaust.

I installed my 785 motherboard in the small Gigabyte case along with my OCZ Gold memory, HD 4650 graphic card, and PII X3 720 processor. Since this case only had one small rear fan I swapped with a heftier Scythe fan. The only difficulty I had with assembly was that the motherboard connector wasn't long enough to reach from the power supply on the case bottom all the way across to the connector at the top of the motherboard. So, I had to get an extension. I also had to get a Molex to SATA adapter for one of the drive power plugs since I ran out of newer SATA connectors (like the drives needed) and only had the older Molex connectors left. My mother had an older 2.0 Ghz dual core system that was a bit clunky. It was slow and the graphics were worse than the embedded graphics on the 785 board. With the faster tricore processor, much greater memory, and considerably more powerful 4650 graphics, my mother is pretty happy with the upgrade.

My two big systems are practically twins, they both have quad processors, 8 GB's of memory, HD 5770 graphics, similar drives, and 200mm cooling fans. The only real difference is that one uses an Intel processor while the other uses AMD. I like both systems. In fact, I'm typing this on my Intel box at the moment.

The i5 750 will run FP faster if the code is tight. This would make a difference in a render farm where even a small difference would effect profitability. However, that doesn't really matter since any commercial use would favor whatever system ran their particular software fastest regardless of anything else. Under some circumstances you can get either AMD or Intel quad to run faster; in actual use I doubt anyone would notice any difference between the two. Since I paid the same amount for each, that is good to know.

I do like the Intel CPU retention better than AMD's. The Intel processor is firmly held in place by itself and this can help keep someone from damaging the unit. With AMD, you have to make certain that you wiggle the heatsink to loosen it BEFORE attempting to remove it. Otherwise the suction of the thermal paste along with the looser pin clamps can cause the processor to pull out of the socket while it is still clamped. This is not a good idea since it can ruin both the processor and motherboard. A novice is less like to damage the Intel CPU. On the other hand, the heatsink retention on Intel boards is noticeably worse than on AMD boards. A novice could also damage an Intel board while trying to install the heatsink. However, if you make sure you understand about inserting the feet all the way through the board and only then pushing the spreader pins in place you'll be okay. Even with the less secure heatsink retention I find Intel boards completely adequate for a heatsink of the size I used (530 grams). To be honest, I wouldn't want to go higher than this with an AMD board either size 500 grams is supposed to be the rated limit. Also, it is hard to beat the price tag of $40 coolers.

Overclocking the AMD Black Edition is a little easier because you can adjust the multiplier. On the other hand, the Intel is easier because of thermal throttling. To be honest though, you can overclock either one fairly easily; I spent many hours at this so I think I have a pretty good idea what is involved. In my experience you are more likely to run into quirks of the particular motherboard you are using. I found for example, that the X3 720 required different overclocking on the 785 board than the X4 965 did even though these two processors should be quite similar. Also, the X4 965 required different technique on the 785 board than it did on the 79X board (even though both were Asus motherboards with ATI chipsets). I can't say this for certain about the i5 since I only had one Intel motherboard but I wouldn't be surprised if  it were the case as well.

I also find it interesting to look at what is available now. I can say with confidence that there is nothing out yet that would make me feel that my systems were outdated. I'll probably look over the new stuff and comment in another article. In particular I've been curious about Intel's on-chip Sandybridge graphics as well as how nVidia is stacking up with AMD's ATI offerings. I wasn't that enthusiastic about AMD's hex core processors but I seem recall that AMD's bulldozer processors will be out soon and they might be worth a look.

Monday, December 14, 2009

New i5 Chip Improves Things Considerably: Stable 3.44 Ghz With Stock Cooler

My previous i5-750 processor turned out to be defective. I sent the chip back to NewEgg and got a prompt replacement. The new processor works much better and well within Intel's specs.

With a properly working processor, it is much easier to see the typical i5/i7 behavior when overclocking. It makes an interesting comparison with AMD. Both Intel and AMD processors are unstable when the voltage is too low. This can be anything from a single thread halting with an error under Prime95 to a hard crash. However, at the top, there is a distinctly different behavior. AMD processors tend to become unstable at some temperature threshold and exhibit very similar behavior to undervolting. The variability is the same, you can see one thread halt or the screen turn to multi-colored gibberish or just go black with a hard crash. Intel processors however don't do this. The problem for Intel is thermal throttling when the chip overheats. Unlike AMD, there is no outward sign that anything has happened. The clock drops to a much lower frequency but the chip just keeps chugging along with complete stabillity. However, the fundamental rules are the same: increased clock requires more voltage to remain stable. More voltage means more heat and eventually both types of processor will reach a point when the voltage is not enough to remain stable but more voltage is too hot.

However, Intel's thermal specs are somewhere between cryptic and endecypherable. If my understanding of these specs has improved then the maximum temperature Intel gives would be the center top of the heat spreader (which we have no way to measure without adding our own probe). Secondly, this spec only defines Intel's guarantee for normal operation within the rated wattage. I suppose this might be useful for an OEM but it doesn't help us much for overclocking. The only real temperature we know for certain is when the chip reaches its maximum Tj and thermal throttles. However, the indicated temperatures of when this happens seem to vary from 5 C low for the stock cooler to 30 C or more low with a good third party cooler. Indicated temperature aside though, for all practical purposes, we can use thermal throttling the an upper limit much the same as an AMD error or crash.

What is Stock?
The first question that usually comes up is what a given chip can do at stock settings. However, one needs to be aware that stock is not exactly defined. Suppose we use 1.225 volts VCORE and 1.1 volts IMC as stock. That is fine; I can set both of these manually in the BIOS. So, I save and exit and then re-enter the BIOS. I bring up the Hardware Monitor and find out that the indicated voltage is not what I set. Likewise, I can boot up Windows and check the voltage with CPU-Z. And, I find out that it says something different from both the BIOS setting and BIOS Hardware Monitor. I'm sure one could argue that one of these is more accurate than the other. However, I chose to use the BIOS setting since it is the only thing I can control. What this means is that when I set the BIOS to 1.225 volts this may be a different voltage than what would be available on a different manufacturer's motheboard or even a different model within the same manufacturer. Nor is there any indication that the Auto setting is a common stock value. Perhaps it is most of the time, but I know that my Asus 785 and 79x boards use different stock voltages. Also, what you test with will change the results. Being able to run SuperPi is no real indication of stability. The same system can boot Windows, complete a SuperPi run, and then crash a few minutes or few hours later with no additional stress. My indications are that:

Prime95 Small FFT < Prime95 Large FFT < OCCT Linpack

In other words, I've had settings that passed Prime95 Small FFT but got errors under Large FFT. And, I've had settings that passed Prime95 Large FFT but got errors under OCCT Linpack. However, I've never had the reverse. I've never a setting pass OCCT Linpack but get errors under Prime95 or pass Prime95 Large FFT but get errors under Small FFT. From what I've seen, this relative stress is the same with AMD and Intel. For example, with Prime95 my Phenom II 965 can pass Prime95 Large FFT at 1.4 volts at 3.8 Ghz. However, my Phenom II 965 cannot pass OCCT Linpack at 3.8 Ghz and 1.4 volts. It needs 1.42 volts to be stable. So, I consider OCCT Linpack to be the definitive test. If it can't pass Linpack then I don't consider it to be stable.

What is Stable?
Once you've tested with Linpack and found the point where it passes but increasing clock will either cause thermal throttling with Intel or thermal instability with AMD then where do you go? I have never considered these points to be usable. In other words, I require some margin between where I will run a system and where it has reached its limits. For example, if the system passed Linpack at 180 Mhz x 20 and got errors at 181 Mhz x 20 then I wouldn't run at 180. I would reduce clock two steps and run at 178 Mhz x 20.

We also need some similar margin with Intel's thermal throttling. My preference would be 5 C. In other words, if a given setting passes Linpack without throttling but higher settings do throttle then I would want to reduce clock and voltage enough to drop the temperature 5 C. This should be enough margin to ensure that with changing room temperature, thermal throttling is never an issue. However, this 5 C number can be a problem. If thermal throttling occurs around 95 C then reducing 5 C seems reasonable. However, using a better cooler can drop the indicated throttling temperature down to the 60's. With this situation, dropping 5 C is not the same. The best I could do would be to try to calculate the same ratio. My room temperature is 23 C so if it throttles at 95 C then that is a 72 C range. That is about 14.5x the 5 C reduction. So, I would probably take the new indicated temperature, for example 65 C, and keep the same ratio. 65 C - 23 C = 42. So, I would only reduce 3 C indicated. These margins are the best guestimates I can come up with; if something turns up later to change these then I'll adjust them accordingly, but this is probably a fairly good starting point.

This is the defective i5-750 that I sent back.

And, this is the new one.

I'm going to do the testing in two parts: first with the stock cooler and then with the Freezer 7 Pro. My case has exceptional cooling with its two 200mm fans. So, I decided that to give a more typical result I would unplug the top 200mm fan for the stock testing. With the rear 120mm case fan and front 200mm case fan running, this should be closer to a typical case with three 120mm fans. When I switch to the Freezer 7, I'll plug the top fan back in. I put the side panels back to close up the case (which is how most cases would be). I also decided on a low tech solution to check temperatures inside the case. I have a clock that gives the room temperature but also includes an outside temperature unit. So, I simply set the outside unit on top of the HD 5770 card which is just below the i5 cooling fan.

This is the outside unit setting on top of the video card.

So here the Indoor temperature is room temperature and Outdoor temperature is the temperature inside the case. The screenshot is convenient because it also documents the time and date. However, even with the top fan turned off my case might still be cooler than average.

My case has the vents on top for the top fan.

And, the left side panel is well ventilated.

Aside from the case ventilation there is also the question of CPU fan setting. My BIOS allows setting for a slower, quieter fan or a faster, noisier fan. I decided to leave the setting at Auto since I don't think all BIOS's have this range. We know that at some point, the stock cooler will be inadequate and the highest fan setting might allow just a little more clock but I don't think this distinction is worth testing since the third party cooler is well above this.

My Results So Far
I'll keep adding results here until I reach thermal throttling with the stock cooler. I would guess that thermal throttling probably won't occur until 3.45 - 3.5 Ghz.

1.225 volts VCORE, 1.1 volts IMC BIOS setting
148 Mhz x 20 = 2.96 Ghz - Linpack stable

1.25 volts VCORE, 1.15 volts IMC BIOS setting
168 Mhz x 20 = 3.360 Ghz - Linpack stable

This is a typical screenshot with the 1.25/1.1 volt test at 3.36 Ghz showing the indicated temperature running about 81 C.

And, this is the clock at the same time showing the case at about 16 C above room temperature.

And, this is the screenshot of the completed Linpack test.

My i5-750 completed Linpack at 1.28125 volts VCORE, 1.20 volts IMC at 3.42 Ghz.

And 3.48 Ghz at 1.30625 volts VCORE and 1.25 volts IMC.

And, finally we find the top:

12/17/09 19:04:15 9.000 0.000 9.000 100.00

We've clearly found the ceiling with the stock cooler. At 1.34 volts VCORE, 1.3 volts IMC at 3.56 Ghz everything shows thermal throttling. With the OCCT graph reading 93 C max we will have to bring it down to 88 C to have a 5 C cushion.

And here is the clock shot showing the temperature inside the case about 20 C higher than room temperature.

I have the OCCT temperature graph handy from the previous 3.48 Ghz speed.

However, this graph touches 90 C. So, I had to come down one step to 20 x 173 Mhz = 3.46 Ghz to pass Linpack with 88 C. Next is the issue of stability. Normally I would drop down 2 steps to 171 Mhz while leaving the voltage at 1.30625 VCORE and 1.25 volts IMC to ensure stability. However, I've already established that this voltage is stable for 174 Mhz. So, using this number we drop two steps to 172 Mhz. And, this gives us our official stock cooler testing speed: 20 x 172 Mhz = 3.44 Ghz. This is a 29% overclock with the stock cooler. Not bad at all.

With Turbo turned on, using the stock cooler, the maximum clock is 165 Mhz which gives about the same speed.

Turbo Off : 20 x 173 Mhz = 3.46 Ghz
Turbo On: 21 x 165 Mhz = 3.465 Ghz

Now it's time to reinstall the Freezer 7 Pro.

Tuesday, December 08, 2009

My Impressions, So Far

I sent my i5-750 processor back to NewEgg last Saturday. I sent it Priority Mail with Insurance and Confirmation. It arrived in Whittier, CA and was accepted by NewEgg yesterday. Hopefully, I'll have a new one in about three days.

Since none of the test data for the i5 was worth anything, I'll just go over my general impressions so far.

Processor and heatsink retention.
AMD processors have pins whereas with Intel the pins are in CPU socket. I prefer the AMD arrangement. An AMD processor should just drop into the socket by gravity. If it doesn't drop in then you probably have a bent pin. I know this well because one of the pins on my PII 965 was bent and I had to straighten it before it would drop in. With the Intel arrangement, half the pins could be bent and you would never know. So, for detecting bent pins, AMD wins.

The second item is the way that the processor is retained in the socket. AMD uses a latching mechanism that grips the pins whereas Intel uses a clamping mechanism that holds the processor down. Here, Intel clearly wins. The clamping mechanism is all metal parts with a metal backing plate; there is no way that this processor is budging. AMD however is a bit worse off. The pin gripping mechanism is not designed to handle pulling loads. Simply put, you must twist the heatsink to break the seal with the processor before you try to remove it. If you just tug on the heatsink, you could end up leaving pins behind in the socket. And, this would almost certainly destroy both processor and motherboard. With Intel, it should be nearly impossible to damage anything no matter how tight the thermal compound is stuck. Be careful with the AMD heatsink and you should be okay but Intel is the clear winner.

Next is the heatsink retention mechanism. I've had both experiences with AMD's. For example, the X3 720 stock heatsink was great; I just put it on and clamped it down. However, the heatsink for the X4 965 was not so nice. The metal loops were too short and I could barely get it on. There was no slack to tighten the clamp. And, you cannot be ham fisted with the clamp because the cam is just made of plastic; I'm sure it will break if you try to force it. The metal loops for the Freezer 64 Pro were just as good as the X3 stock unit; it just went on and clamped into place without any trouble. AMD's mechanism works the same whether it is third party or stock and the retention frame uses a metal plate on the back of the motherboard for extra strength much as Intel does with the CPU clamp.

Intel however seems to have more than one way to hold the heatsink on. The stock unit uses pins that push down through the four holes surrounding the rentention frame. You push opposite diagonals at the same time. I unlocked the pins, then pushed the pins through and twisted the knob on top of each leg to clamp the pin in place. Apparently, however, you can just push the knobs down while in the locked position. This is maybe a tiny bit easier than the way I did it. Either way though, you want to make sure that each knob is down, locked, and the pin firmly attached to the motherboard. The Freezer 7 uses a completely different method. it has a plastic frame that goes around the CPU clamp frame. You have to push plastic pins through the holes in the frame and through the holes in the motherboard. Then you push expander plugs into each pin to keep them from coming loose. This operation is much more than a pain; it is sloppy and includes far too many ways that you could break or damage the plastic parts. I had to push the retaining plugs in (and remove them later) with needle nosed pliars. And, they take a fair amount of force to push in and pull out. I don't know if these are all similar with third party coolers on Intel motherboards but the Freezer 7 requires patience and a fair amount of care before you apply force. Then, once you have the plastic frame mounted you attach the actual heatsink bracket with two screws. You have to remove the fan to have room to insert the screw on that side. And, fiddling with the other screw in the cramped space between the heatsink and rear case fan is also not much fun.

With AMD, as long as you have a third party cooler that uses the stock latching mechanism then the AMD system is much easier to change processors. With Intel, at least with the Freezer 7, the heatsink bracket blocks the CPU clamp so you cannot change processors without first removing the plastic bracket. This is a major pain. Still, most people probably wouldn't be swapping processors very often so it's probably a hassle that one can live with. I think both of the systems can work with a 500 gram cooler but I wouldn't trust either one of them with anything heavier. Both designs have shortcomings which could result in damaged parts if you aren't careful. However, both systems can (and I'm sure they do) work most of the time.

Changing Clock Speed
I've only worked with Asus motherboards. It is interesting though how different the flavor of the BIOS is from AMD to Intel. My 785 board has few options even though my X3 is Black Edition which allows easy overclocking. The BIOS works fairly well with the X3 just in terms of overclocking. There are items that are mislabeled in the BIOS, for example, calling something a clock setting when it is actually a multiplier setting. And, I have to say that I don't understand why the Intel BIOS nicely calculates memory speed based on actual base clock whereas the AMD memory speed always uses a base clock of 200 Mhz for its calculations. Someone is clearly dropping the ball here.

However, with the X4, it was another story; it wasn't until I realized that the BIOS was setting the voltage too high and reduced it that I could get it stable at higher settings. This amounted to a bump of at least 100 Mhz. The 79X board is a different flavor. It has more settings and is a little easier to use. However, it seems to set the default voltage lower than on the 785 board. I couldn't get 3.9 Ghz stable running OCCT Linpack without bumping the voltage to 1.425 (when 1.4 volts is AMD's max for this chip). The 785 BIOS is adequate but, when using the PII 965, I like the 79X BIOS a little better. I would guess that this BIOS is more like that of the older 78FX boards.

The Intel BIOS on my P55 motherboard is a bit more polished. As I've already mentioned it correctly displays memory speed even when you change the base clock from 133 Mhz. The disappointments come more from the processor itself. Since regular Intel processors have a locked multiplier they aren't nearly as easy to overclock as AMD processors. You really have to stretch that base clock setting to hit anything substantial (at least with the i5-750 which only has a base clock of 2.66 Ghz). For example, to hit 3.32 Ghz you have to bump the clock from 133 to 166 Mhz. This wouldn't be so bad if it weren't for memory. For example, with the base clock at 166 Mhz you can set the memory multiplier the same as for 1066 Mhz and it will actually be at 1333 Mhz. Likewise you would hit the same 1333 Mhz speed again with a base clock of 222 Mhz if you set for 800 Mhz. Of course, with a standard multiplier of 20, this would be 4.44 Ghz on the processor which is out of the question. However, since Intel has no problem with reducing the multiplier you could just set this to, say, 16 or 17, and get an accessible processor clock. It does work, just not as well as with Black Edition. Naturally, not all of AMD's processors are Black Edition but Intel has nothing remotely like this below the outrageously priced i7-965. Maybe Intel thinks that Turbo makes up for some of what is lacking but I would rather see unlocked multipliers. Finally, I'll mention the x21 multiplier because I've seen this mentioned in several reviews. My BIOS can be set to a multiplier of 21 but is doesn't work; the highest multiplier you can actually set is 20 (the same as the default).

Overall, AMD seems a little easier because of the unlocked multiplier, but if the Intel chipset and processor are able to tolerate base clocks way over the default 133 Mhz, Intel could still end up the winner. It will be interesting to find out.