Investigations into Socket 939 Athlon 64 Overclocking
by Jarred Walton on October 3, 2005 4:35 PM EST- Posted in
- CPUs
BIOS Settings
Once everything is working properly and you're sure that the PC doesn't have any problems, it's time to approach the actual process of overclocking. You might want to give the PC a few days of heavy use (system burn-in) just to be sure that it's stable. All of the FutureMark benchmarking utilities are a good start for stress testing a system, and if you buy the registered versions, you can set them to loop continually - at least, the 3DMark versions can be looped; a quick batch file will get the PCMark applications to loop as well. If you can loop 3DMark03/05 and PCMark04/05 for several days, you can be relatively sure that the computer is running stable. We'll use that same approach later to stress test our overclocked configurations.
Here's where things get more complex, and virtually every motherboard BIOS is going to be at least slightly different from what we present here. If you have a socket 939 motherboard, you'll need to refer to its manual (or figure out where the settings are on your own), but most of the names and/or values will be similar to what DFI uses. The key areas that will need adjustment for overclocking are the CPU bus speed, CPU multiplier, HyperTransport (HT) multiplier, memory speed, memory timings, and voltages for RAM, CPU, chipset, etc. Let's cover each of these quickly to explain the process. We'll include BIOS images from our particular motherboard, so you can look for the matching setting in whatever board you're using.
The CPU bus speed is also referred to by other names. The DFI board labels it "CPU Frequency", while you may find HyperTransport Frequency in many BIOSes. (Some people will also call it the "Front Side Bus speed", which is not technically correct.) CPU Frequency, CPU Bus, HT Bus, etc. all mean the same thing, as the CPU communicates over an HT bus. Along with the CPU multiplier, there is also a HT multiplier (also called LDT - Lightning Data Transport - multiplier in some BIOSes). Most socket 939 motherboards support a 1000MHz HT speed, which is a 5X HT multiplier with a 200MHz base clock. The HyperTransport bus is sensitive to overclocking, so we need to keep its total speed in check. You may be able to run the HT bus at over 1000 MHz, but depending on motherboard and cooling, you will begin to have problems beyond a certain point. We'll keep our HT bus speed at or below 1050MHz by adjusting the HT multiplier as we increase the CPU bus speed (and we may at times drop lower if that brings stability). We can use the 4X multiplier with up to a 260MHz bus, and 3X will get us up to a 350MHz CPU bus (which is more than what most people are likely to reach, and more than what we'll test in this particular article). It is also possible to adjust the width of the HT bus from 16-bits up and down to 8-bits, but rarely does that help stabilize an overclock, so we'll leave it at 16/16.
We've covered the CPU and HT speed adjustments, but there's more to it than simply picking a target clock speed. In order to reach a stable overclock, you will often need additional voltage to the CPU and chipset - which affects the CPU speed and HT bus speed respectively. The default voltage of our Venice chip is 1.300V, but we will definitely increase the voltage as we go beyond a 10% overclock. Extreme overclocking (with liquid Nitrogen or phase change cooling) might go so far as to double the CPU voltages, but on air cooling that would be disastrous (not to mention few if any motherboards would even support that in the first place). We'll report the voltages required for each setting later on, but there are really two voltages: what we set in the BIOS, and what we actually get from the system. They may or may not be the same.
Something else that you should disable while in the BIOS is the Cool 'n Quiet feature of the Athlon 64. As that alters CPU voltage and multipliers dynamically in response to demand, it doesn't usually agree with overclocking. We also disable video and BIOS caching, as those are more relics of the DOS era than useful features (as far as we're aware). If you're interested in seeing the default settings that we used on the remaining BIOS screens, we have all the BIOS screens available for download in a Zip file.
Once everything is working properly and you're sure that the PC doesn't have any problems, it's time to approach the actual process of overclocking. You might want to give the PC a few days of heavy use (system burn-in) just to be sure that it's stable. All of the FutureMark benchmarking utilities are a good start for stress testing a system, and if you buy the registered versions, you can set them to loop continually - at least, the 3DMark versions can be looped; a quick batch file will get the PCMark applications to loop as well. If you can loop 3DMark03/05 and PCMark04/05 for several days, you can be relatively sure that the computer is running stable. We'll use that same approach later to stress test our overclocked configurations.
Here's where things get more complex, and virtually every motherboard BIOS is going to be at least slightly different from what we present here. If you have a socket 939 motherboard, you'll need to refer to its manual (or figure out where the settings are on your own), but most of the names and/or values will be similar to what DFI uses. The key areas that will need adjustment for overclocking are the CPU bus speed, CPU multiplier, HyperTransport (HT) multiplier, memory speed, memory timings, and voltages for RAM, CPU, chipset, etc. Let's cover each of these quickly to explain the process. We'll include BIOS images from our particular motherboard, so you can look for the matching setting in whatever board you're using.
Click to enlarge.
The CPU bus speed is also referred to by other names. The DFI board labels it "CPU Frequency", while you may find HyperTransport Frequency in many BIOSes. (Some people will also call it the "Front Side Bus speed", which is not technically correct.) CPU Frequency, CPU Bus, HT Bus, etc. all mean the same thing, as the CPU communicates over an HT bus. Along with the CPU multiplier, there is also a HT multiplier (also called LDT - Lightning Data Transport - multiplier in some BIOSes). Most socket 939 motherboards support a 1000MHz HT speed, which is a 5X HT multiplier with a 200MHz base clock. The HyperTransport bus is sensitive to overclocking, so we need to keep its total speed in check. You may be able to run the HT bus at over 1000 MHz, but depending on motherboard and cooling, you will begin to have problems beyond a certain point. We'll keep our HT bus speed at or below 1050MHz by adjusting the HT multiplier as we increase the CPU bus speed (and we may at times drop lower if that brings stability). We can use the 4X multiplier with up to a 260MHz bus, and 3X will get us up to a 350MHz CPU bus (which is more than what most people are likely to reach, and more than what we'll test in this particular article). It is also possible to adjust the width of the HT bus from 16-bits up and down to 8-bits, but rarely does that help stabilize an overclock, so we'll leave it at 16/16.
We've covered the CPU and HT speed adjustments, but there's more to it than simply picking a target clock speed. In order to reach a stable overclock, you will often need additional voltage to the CPU and chipset - which affects the CPU speed and HT bus speed respectively. The default voltage of our Venice chip is 1.300V, but we will definitely increase the voltage as we go beyond a 10% overclock. Extreme overclocking (with liquid Nitrogen or phase change cooling) might go so far as to double the CPU voltages, but on air cooling that would be disastrous (not to mention few if any motherboards would even support that in the first place). We'll report the voltages required for each setting later on, but there are really two voltages: what we set in the BIOS, and what we actually get from the system. They may or may not be the same.
Something else that you should disable while in the BIOS is the Cool 'n Quiet feature of the Athlon 64. As that alters CPU voltage and multipliers dynamically in response to demand, it doesn't usually agree with overclocking. We also disable video and BIOS caching, as those are more relics of the DOS era than useful features (as far as we're aware). If you're interested in seeing the default settings that we used on the remaining BIOS screens, we have all the BIOS screens available for download in a Zip file.
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Deathcharge - Saturday, October 15, 2005 - link
also what do you think of opteron 144 or 146? the 144 are very cheap and they OC quite well apprentlypmorcos - Thursday, October 13, 2005 - link
Before I comment, you should know that I have been overclocking for 8 years now and literally overclocked all but one of the chips you mentioned in the beginning of this very good article. The HT multiplier was new to me with my most recent DFI NF4-SLI-DR board so I found that extremely useful and plan to see if I can up my speeds...but I digress.I think it would be extremely valuable to TRY to put in words the order with which an overclocker should approach making changes to settings. In other words, which is likely to be the most limiting/critical aspect(s) and from there tweak the others to max the system out.
It would be interesting to say, for example, that you start with a "safe" power settings (which is pretty obviously the limiting factor). For example, let's say your CPU and memory are rated at 1.3 and 2.8 V respectively. Why not go straight to "safe" settings for the two and tweak from there? It seems that the most useful piece of information that is NOT provided by anandtech or anyone else for that matter is a voltage and temp graph of stability/viability for these chips. It would be simple to take 3 samples (at a cost) of each chip and run the test with "average" cooling and find out what is "safe". For example if running all stock settings but upping voltages to say 2.4/3.6 V in the example above, you might see stability up to 1.65 / 3.1 V with the parts catching fire at say 1.8/3.3 V or stable at temp readings for cpu/memory of 44/47C but unstable above that. Once armed with these two graphs of information averaged from 3 chips tested the rest is very straight forward.
You simply set the cpu volts to 1.65 and memory to 3.1 V (the safe settings; check real voltages vis bios monitoring) and now you up your fsb and tweak your memory timings and in a few minutes you are running max.
Why do I think this is more valuable that showing us a graph of your results? Because like many I'm squeemish about upping the voltage on my processor and memory. I'm worried much more about the power-on affects than I am the "long-term" effects.
In computers, there are no long-terms for an overclocker. An overclocker's comp is 60% hardware and 40% software. Their greatest joy is in posting results on their favorite forum. I want to know that when I hit the power button...that the 1.7V setting does NOT have a 10% chance of blowing my processor.
My ramblings. Thanks again for another great article from by far the VERY BEST place in the world to find out how computer parts work.
JarredWalton - Thursday, October 13, 2005 - link
Thanks pmorcos.I'm working on the X2 3800+ OC followup, and I've gone back and done further testing of temperatures and voltages. Chips differ, so the real advice I have on that subject is to test your own chip extensively. I've heard of people doing 2.8 GHz on 1.500V with the Venice chips, but mine won't even POST at those settings. I think 1.65 or 1.70V was required to POST, and even then I couldn't run stable benchmarks without more voltage.
I will also be trying to cover a bit more of the "how to" process in the next one. Consider this the foundation, and the next article will refine the approach a bit. Your comments on what you'd like to see more of are definitely welcome, though, and I'll try to address the order and approach I take next.
Concerning another comment: "I want to know that when I hit the power button...that the 1.7V setting does NOT have a 10% chance of blowing my processor." I'm not quite sure I understand the concern or know how to test that. Are you saying that the power on process has more voltage fluctuations and may therefore toast the CPU in the first second? (I haven't had that happen over the past several months of testing this chip and others in overclocked setups.) I must admit that I'm extremely nervous about the 1.850V I used for running at 2.80 GHz, but even then the chip continued to function (for now - heheh).
Cheers!
Jarred Walton
WhipperSnapper - Thursday, October 13, 2005 - link
That was one of the best computer enthusiast website articles that I've read in a long time, but perhaps I don't get around too much. I'd like to hear more about the problems that spilled over to other components, such as the SATA hard drive (mentioned in the Final Thoughts) and whether or not the overclocking can be isolated to the CPU and RAM. I also wondered if there was a reason why you guys used a SATA hard drive and not an IDE drive and whether overclocking requires a SATA hard drive. (I don't see why it would.)
Also, have you guys tried to do any tests using memory stick heatsinks? Do they actually do anything? That subject might make for a worthwhile article on its own--RAM cooling.
aptinio - Saturday, October 8, 2005 - link
bravo! great article. very informative but not too bloated. can't wait to finally upgrade my amd k6-II with 1mb l3 cache on the motherboard! lol!Kougar7 - Thursday, October 6, 2005 - link
Thank you for the excellent, comprehensive, and very thorough article! :-) It must have taken a massive amount of work and time to complete. It’s answered my recent musings about my own Crucial value ram, which looks much nicer now! It’s also solved a question about OCing with recent AMD 64 chips, amongst also correcting a few personal misconceptions I’ve had.I just wish to ask if you plan to include a similar article on OCing with P4s? I personally run a 2.8C (Northwood) @ 3.4 rock solid at the 3.4C’s default voltage, but am now wondering exactly what performance hits, if any, that I’ve taken from having to use a 5:4 CPU:DRAM ratio instead of the previous 1:1, even though I’ve kept it at DDR390 and the timings better than specs.
I’m planning to bench the differences from a 1:1 ratio, a 3:2 ratio at highest speed I can get (sub-DDR333), my current setup, and finally one other setting where I got the value memory to run 2-2-2-6 timings, to get a more solid idea on which performs best with some solid figures.
Although the core and the platform itself both have both changed, I’d still be interested in a Intel processor based test! Perhaps instead of a P4, maybe a Pentium “D” OCing article similar to what you have planned with the X2 3800+? ;-)
I’m very much looking forward to your X2 3800+ OCing review!! You rock :-D Thanks in advance for it!
JarredWalton - Thursday, October 6, 2005 - link
I'm trying to get a socket 775 motherboard that will overclock well with Pentium D 820. Once I get that, I can give it a go. I've also got a Pentium 4 505 and a 540 that I want to run some similar tests on. First, though, I need an appropriate motherboard.clue22 - Thursday, October 6, 2005 - link
so basically what the everybody is saying about the value RAM vs. low latency more expensive RAM is that for the athlon 64 it is basically a waste of money (i.e. you only get about 5% performance gain), but usually spend 100% or more money to get the "better" RAM. i have to build a couple of systems pretty soon and now i believe that my money would be better spent on 2GB of value RAM vs. 1GB of the more expensive stuff. does anyone know of a test that has been run with 2.5-3-3-8-1t vs. 2-2-2-5-1t? also why does every mid-range/gaming/hot-rod price guide ever recommend the either the samsung tccd (or tcc5) or winbond bh5/ch5 based memory if it has so little effect on performance. finally is it even important anymore (if it ever was) to get matched pairs of memory that are bundled together (supposedly manufactured at the same time)? i was looking at some corsair (had good experience with them in the past) xms3200xl RAM but now i think i should get more of their value select memory instead.thanks
RupertS - Wednesday, October 26, 2005 - link
so basically what the everybody is saying about the value RAM vs. low latency more expensive RAM is that for the athlon 64 it is basically a waste of moneyThis may not be a general rule.
It may just be that at this stage of development for GPU's, CPU's and memory, memory has more than enough capacity - it is not the choke point. If GPU and CPU speed were to improve while memory speed stayed the same, you might reach the point where increasing GPU and CPU speed was non-productive for games, while overclocking memory provided large performance improvements.
rabbit fighter - Wednesday, October 5, 2005 - link
Where was this explained? He said the 3200 was better in the first paragraph and that he would explain later, but I can't find the later explanation!