I just recently got through overclocking an Athlon 64 X2 3800+ system to 2.55ghz and thought I might share my experiences in case it might help someone not encounter all the trouble I went through :haha:
First off, here are the specs I started out with
Gigabyte K8N-SLI (apparently not the best board to OC with, but it worked in the end)
Athlon 64 X2 3800 (Week 33, '05. stock: 2ghz per core)
Antec Neo HE 500w power supply
BFG Geforce 7800 GT OC (stock: 425 / 1.05)
2x1024mb of OCZ Platinum PC3200 (stock: 400mhz CL2, 3-2-5)
Random Soundblaster Live that was laying around the house
Linksys Wireless card
Windows XP x64 edition
OK, so the board starts out at 200mhz, with a 5x multiplier for Hypertransport speed, for a total of 1,000mhz. This, as I found out after days of trial and error, is the key to any overclocking walls with this particular setup.
My initial attempts involved simply raising the 200mhz bit by bit. First to 205, then a quick round of benchmarks, then 210, and a quick round of benchmarks. So far so good. Wham. It hits the fan. Board won't even get past the POST screen at 215.
I tried raising the timings of the memory in case it was simply a bad set (as OCZ is particularly known for being able to go beyond stock at the tight timings it is rated at) - no go. I tried lowering the CPU multiplier, no go. I tried raising all the voltages, no go. On a somewhat related note, this board does not allow you to specify exact voltages for anything except the CPU. The chipset, DDR, and HT voltage settings are only expressed in values of +0.n - the maximum for which is +0.3, +0.2, and +0.3 respectively, and all of which I have set to maximum. The CPU can go anywhere from 0.8v to 1.75v in varying increments, so I attempted a massive 1.75v overvolt on the CPU to get it to emit any signs of life. Don't try this at home. In fact, I wouldn't even recommend that I try that anymore. Cause it still didn't work.
Then it dawned on me that the HT might be sensitive to overclocking, so I lower it down to 4x. Damn. Lower it down to 3x. 2.5x. 2x. 1.5x. Still nothing. Then I hit the bottom of the barrel, 1x, essentially bringing the HT bus to the same level as a regular old DDR FSB. Well, whaddya know. It posts. And boots. And benchmarks quite nicely.
I start getting a little crazy and pumping up the FSB. 220 goes by without incident. 230. I stop at 233 and check to make sure everything is stable - folding@home, Prime95, Sandra, 3dmark, etc. because I just like the number 233 (incidentally, that's faster than the first CPU that I recall being fast - the Pentium 133) and ironically enough, that's as high as the board will go. So at this point I'm still wondering if there is any possible way to squeeze more juice out of it now that I've hit the RAM's expected wall (I read on OCZ support forums that 230mhz is typically the highest that this particular model will go).
There is a feature on my board to run the RAM at a different clock speed vs. the FSB and I expect that any decent board not made to put in a Compaq computer will be able to use this feature... I made use of it to run the RAM divider at 2 / 1.83, and started on my FSB pumping journey again. 240. 245. 250. All whizzed by with no problems (outside of the occasional needing to bump the voltage on the CPU). At this point I was quite satisfied with the overclocking performance of my processor and board, as benchmarks went by without a hitch and the system was noticeably snappier - even moreso than when I initially installed it, having known previously only a single CPU system with generic RAM at crap timings.
I decided to push it to the very limit. 255 FSB, leaving the RAM at the max 466 (due to the divider) - and overclock the video card as well. Since I had already found out the video card's maximums before I started going nuts on everything else, this part was rather painless. A quick run of the NVTray application to enable Coolbits overclocking on my new Windows install, then I go in and crank it up to 495mhz core, 1.2ghz memory (apparently not the best overclock for the card, but it'll do for me).
What is it now?
Athlon 64 X2 3800 @ 2.55ghz, 1.65v (faster than an X2 4800 and more able to leap tall buildings in a single bound)
BFG Geforce 7800 GT OC @ 495 / 1.2
2x1024mb of OCZ Platinum PC3200 @ PC3700, CL2.5, 3-3-6, +0.2v
All on air cooling. The Athlon 64 X2 is the only item that contains aftermarket cooling hardware - the Zalman CNPS7700Cu with the fan controller set to high.
At this point I start up the benchmarks and prepare to **** my pants (Sorry for the expletive but it's justified, damnit
)
SiSoftware Sandra
Benchmark Results for CPU Arithmetic
Dhrystone ALU : 24948 MIPS (beats out all of the reference scores)
Whetstone iSSE3 : 10834 MFLOPS (bested only by the Pentium 4 reference score)
Benchmark Results for Memory Bandwidth
RAM Bandwidth Int Buff'd iSSE2 : 6425 MB/s
RAM Bandwidth Float Buff'd iSSE2 : 6372 MB/s
Both scores mopped the floor with even the best reference score
3dmark05 Pro
Complete benchmark (Default settings, except ALL tests checked in the selection dialog), with the video card settings at highest performance
8,417 3dmarks (7,177 CPU marks) - compare: http://service.futuremark.com/compare?3dm05=1696074
Observations
Hope this mess of text happens to help someone in the same situation, and if not, I hope it at least entertained you.
First off, here are the specs I started out with
Gigabyte K8N-SLI (apparently not the best board to OC with, but it worked in the end)
Athlon 64 X2 3800 (Week 33, '05. stock: 2ghz per core)
Antec Neo HE 500w power supply
BFG Geforce 7800 GT OC (stock: 425 / 1.05)
2x1024mb of OCZ Platinum PC3200 (stock: 400mhz CL2, 3-2-5)
Random Soundblaster Live that was laying around the house
Linksys Wireless card
Windows XP x64 edition
OK, so the board starts out at 200mhz, with a 5x multiplier for Hypertransport speed, for a total of 1,000mhz. This, as I found out after days of trial and error, is the key to any overclocking walls with this particular setup.
My initial attempts involved simply raising the 200mhz bit by bit. First to 205, then a quick round of benchmarks, then 210, and a quick round of benchmarks. So far so good. Wham. It hits the fan. Board won't even get past the POST screen at 215.
I tried raising the timings of the memory in case it was simply a bad set (as OCZ is particularly known for being able to go beyond stock at the tight timings it is rated at) - no go. I tried lowering the CPU multiplier, no go. I tried raising all the voltages, no go. On a somewhat related note, this board does not allow you to specify exact voltages for anything except the CPU. The chipset, DDR, and HT voltage settings are only expressed in values of +0.n - the maximum for which is +0.3, +0.2, and +0.3 respectively, and all of which I have set to maximum. The CPU can go anywhere from 0.8v to 1.75v in varying increments, so I attempted a massive 1.75v overvolt on the CPU to get it to emit any signs of life. Don't try this at home. In fact, I wouldn't even recommend that I try that anymore. Cause it still didn't work.
Then it dawned on me that the HT might be sensitive to overclocking, so I lower it down to 4x. Damn. Lower it down to 3x. 2.5x. 2x. 1.5x. Still nothing. Then I hit the bottom of the barrel, 1x, essentially bringing the HT bus to the same level as a regular old DDR FSB. Well, whaddya know. It posts. And boots. And benchmarks quite nicely.
I start getting a little crazy and pumping up the FSB. 220 goes by without incident. 230. I stop at 233 and check to make sure everything is stable - folding@home, Prime95, Sandra, 3dmark, etc. because I just like the number 233 (incidentally, that's faster than the first CPU that I recall being fast - the Pentium 133) and ironically enough, that's as high as the board will go. So at this point I'm still wondering if there is any possible way to squeeze more juice out of it now that I've hit the RAM's expected wall (I read on OCZ support forums that 230mhz is typically the highest that this particular model will go).
There is a feature on my board to run the RAM at a different clock speed vs. the FSB and I expect that any decent board not made to put in a Compaq computer will be able to use this feature... I made use of it to run the RAM divider at 2 / 1.83, and started on my FSB pumping journey again. 240. 245. 250. All whizzed by with no problems (outside of the occasional needing to bump the voltage on the CPU). At this point I was quite satisfied with the overclocking performance of my processor and board, as benchmarks went by without a hitch and the system was noticeably snappier - even moreso than when I initially installed it, having known previously only a single CPU system with generic RAM at crap timings.
I decided to push it to the very limit. 255 FSB, leaving the RAM at the max 466 (due to the divider) - and overclock the video card as well. Since I had already found out the video card's maximums before I started going nuts on everything else, this part was rather painless. A quick run of the NVTray application to enable Coolbits overclocking on my new Windows install, then I go in and crank it up to 495mhz core, 1.2ghz memory (apparently not the best overclock for the card, but it'll do for me).
What is it now?
Athlon 64 X2 3800 @ 2.55ghz, 1.65v (faster than an X2 4800 and more able to leap tall buildings in a single bound)
BFG Geforce 7800 GT OC @ 495 / 1.2
2x1024mb of OCZ Platinum PC3200 @ PC3700, CL2.5, 3-3-6, +0.2v
All on air cooling. The Athlon 64 X2 is the only item that contains aftermarket cooling hardware - the Zalman CNPS7700Cu with the fan controller set to high.
At this point I start up the benchmarks and prepare to **** my pants (Sorry for the expletive but it's justified, damnit
)SiSoftware Sandra
Benchmark Results for CPU Arithmetic
Dhrystone ALU : 24948 MIPS (beats out all of the reference scores)
Whetstone iSSE3 : 10834 MFLOPS (bested only by the Pentium 4 reference score)
Benchmark Results for Memory Bandwidth
RAM Bandwidth Int Buff'd iSSE2 : 6425 MB/s
RAM Bandwidth Float Buff'd iSSE2 : 6372 MB/s
Both scores mopped the floor with even the best reference score
3dmark05 Pro
Complete benchmark (Default settings, except ALL tests checked in the selection dialog), with the video card settings at highest performance
8,417 3dmarks (7,177 CPU marks) - compare: http://service.futuremark.com/compare?3dm05=1696074
Observations
- The HT bus speed multiplier did not seem to have any discernible effect on the speed of the system, either perceived or benchmarkable. It seems that nothing quite saturates a DDR 255mhz FSB quite yet, so a HT multiplier of 1x doesn't bother me a bit since it allows me such a great overclock.
- Overclocking the FSB to 266 (keeping the processor at the 10x multiplier still) and lowering the RAM divider to make it run at 441mhz lowered the RAM bandwidth to 6.3gb but was a higher percentage of the bus's potential speed than 6.4gb at 466 - 90% vs 85%. Thus, it seems that memory bandwidth efficiency is positively affected by a faster processor which makes sense since the controller is on the chip instead of the board. I imagine people with elegant liquid cooling setups can manage an even higher overclock and thus enjoy an even higher percentage of use of the available memory bandwidth. Unfortunately the system was not stable enough at this speed to finish 3dmark
- AMD processors rock
- OCZ ram rocks
- Rocks don't feel particularly well when bashed against one's head
- I overclocked as many MHz out of these two cores as I had on my previous system altogether: 1100 MHz
Hope this mess of text happens to help someone in the same situation, and if not, I hope it at least entertained you.
