View Full Version : Oc'ing my amd64-how high should I set the FSB?

09-07-04, 07:07 PM
Should I set the FSB in increments of 5 or 10? Right now it's @ 200.....I got it to 210....which is @ 2100ghz....I'd like to get it to 2200...is that about 215? Anyone else with an A64 your input would be appreciated! Also...some people told me i'll need to change the latencey of my memory timings along with my fsb-while others said I dont...which is it? I really hate to mess with memory timings....just not my thing....trying to squeeze what I can out of my system, between a 200mhz oc to my cpu and oc'ing my gpu to ultra speeds...I'm hoping for a 8-10 fps gain in games. :)

09-07-04, 07:29 PM
If your MoBo has a PCI/AGP frequency lock make sure it is turned on. I don't have one and it still works great, but do it anyway.

Its pretty difficult to cause any damage to your computer by overclocking as long as you are fairly careful. I just kept on increasing in increments of 5 Mhz until it wouldn't POST anymore. Then I turned it down to the last setting I had. Then I booted and ran Prime95. It normally crashes after about a minute like this. Then I went back to BIOS and kept on decreasing 2-3 MHz at a time until Prime95 no longer crashed at all. To know if it won't crash ever, you really need to run Prime95 for at least 18 hours IMHO.

If you don't know what Prime95 is just search on google. Its a program that calculates Pi [EDIT: No it doesn't. I made this up because I couldn't think what it did exactly at the time. It calcultates Prime numbers to very very high digits not Pi.] to many many digits and is very very CPU and Memory intensive. The site explains how it can be used a Stress Test for Overclockers...

Anyway, just as an example: I found it wouldn't POST at about 2.55GHz. Thats 255MHz FSB. Then I kept on turning it down by 2-3 MHz. It seemed stable at around 2.48GHz, but I found it wasn't completely stable until 2.45GHz (and then I turned it down to 2.40GHz because I wanted the temps to around 60-65 not 65-70). The clock frequencies should simply be 10xFSB unless you have changed the multiplier which I don't think any MoBos allow yet.

I did mine with stock cooling and these are the best results I have seen yet with such a setup. I'm not bragging but just saying I wouldn't be too disappointed if you only get up to 2.3GHz or so. My values do not seem to be the normal.

Oh try incresing your CPU Core Voltage to increase stabilty, and constantly check temps while doing this as this is where you can cause damage. I run at 1.70V Core which is above recommended AMD spec. but my temps never go above 60C on the CPU temp. which is hot but still well within safe limits (I would say 70C is an upper safe limit but mighty hot)...

Hope this hasn't been too patronising if you already know all this and Good Luck! :)

09-07-04, 07:38 PM
Oh sorry, I forgot about memory timings. Well generally Mem timings will probably have to become higher (as in slower) to keep your system stable. If you have poor quality memory then OC to any worthwhile distance may be impossible.

If on the other hand you have Memory that is stable as a rock at 2-2-2-5, you may like me have to change to 2.5-3-2-6 or something similar. IMHO the tradeoff is well worthwhile. I only had to change mine from 2-2-2-5 to 2-3-2-5.

Also I had to chenge my ratio to something lower so that I wasn't running my memory at 420-odd MHz. Its very good to have really high quality memory when overclocking. I feel its probably the most important part. I think my biggest problem with clocking further is not CPU-limited or MoBo limited but rather I have hit the max clock frequency for my RAM. I wish I had invested in the PC3700-type (466MHz) or PC4000-type (500MHz).

09-07-04, 07:47 PM
Thanks for the answers.....one question...where should I set the cpu core voltage 1.60?

09-07-04, 07:52 PM
one more question...what would happen if I just messed with the FSB and nothing else....lets say I set my FSB to 220...is it possible for things to run stable without needing to volt mod and change latencey.....

09-07-04, 07:58 PM
you might need to up the volts to for the cpu to run stable...

I have had my setup running at 215mhz fsb w/o problems on stock volts but I made sure stability was rock solid... prime as well as running loops of a bench app are a good way of testing...

it also helps if you have an agp/pci lock... that it the primary reason I have not experimented more...

09-07-04, 09:40 PM
The A64 CG stepping, the newcastle core, seems to overclock well on stock voltage.

This is going to sound ridiculous, but mine runs stably at 10x235, 2350mhz, with the vcore at 1.4v, 0.1v UNDERvolt, and that's my bios's idea of 1.4v, which means about 1.35-375v in actual voltage provided to the cpu.

I don't keep it at 235fsb though, as i've only had it a month, so i run it at 220fsb for now, i'm saving the extra 150mhz of power for down the line when i'll really appreciate it.

Basically i wouldn't put your core voltage up on a newcastle core A64 because it doesn't really provide much benefit unless you put it very high, i like to undervolt mine and dial the fan down to save on noise and heat, why create extra if there's no need.

09-07-04, 11:32 PM
Hmm my amd 64 3400+ doesn't o/c very well. Might just be pci/agp lock has to be on. Cause the load temp is around 42C on stock cooling. Think I got enough air flow in the case. Even fsb at 210 causes instability. This is with the vcore at 1.55 volts. Should I increase the memory voltage or not? Does it make a difference?

09-08-04, 06:18 AM
Annihilist: Not really sure if it will help you or not. If you are willing just give it a go, but remember that raising core voltage any higher is above AMD recommended values for the chip. The most important thing while doing this is to check temps while loading the CPU (use the software that probably came with your MoBo to monitor).

I personally say if ever goes higher than 70C then you have gone too high, but really it shouldn't go much higher than 60C if you're looking for long-term safety of the chip. I can't say for sure but at 70C it is said that the chip won't live for as long. Well considering CPUs are supposed to last for a hundred years or more, I don't see this as a problem, but others say it might reduce the chip's life to just a few years (like 4-5 years). As the chip hasn't been out that long I can't tell you which is the truth. Besides, I intend to have water cooling before the next couple of years when they go down in price a bit, and that should increase life.

ultimate17: Answered your PM. Probably best to keep any convo in here though in case anyone else is interested, or has input. :)

09-08-04, 09:33 AM
I just can't maintain stability even at 210 on the fsb. My temps are fine. Can it be a memory issue?

09-08-04, 09:58 AM
Well try the CPU Core voltage thing first. You might still be under-powering the chip for anything higher than the default.

Yes, it very possibly could be the RAM. Best way to check for that is to change the FSB:Mem ratio to its lowest so that RAM is underclocked and see if you still get instability when clocked at 210FSB.

09-08-04, 04:26 PM
I've just done some investigating, and i found my newcastle A64 3000+ will do 10x250=2.5ghz at 1.6v, that's with htt at x3 and my cheap ram at 5:6 DDR416.

Sandra cpu score puts that at over 11200 alu, just faster than a p4 3.8Ghz.

However i'm happier running it 10x225=2.25ghz at 1.4v, htt x4, it's over 10c cooler, plus my ram is at 1:1 DDR450, which i think is better considering the s754 only runs single channel, memory bandwidth is a commodity. Sandra puts the ram bandwidth at 3350MB/s, compared to 3050MB/s if i run 2.5ghz.

09-09-04, 09:20 AM

might give you some ideas on how overclockable your CPU is

09-09-04, 02:40 PM
npras42 is completely right about having good RAM when overclocking. I had some cheap Corsair PC3200 before and I just upgraded to some PC4000 Crucial Ballistix. In terms of overclocking they are worlds apart. I couldn't overclock at all with the Corsair unless I had a ridiculous ratio between the FSB and the RAM where the FSB was much higher than the RAM was.

Now I have the FSB and RAM on a 1:1 ratio running 250x10. I love this RAM. Up to about 220 FSB it will run with timings of 2-2-2-5. Now I'm running it at 250 I put the timings to their default for PC4000 which is 2.5-4-4-8.

Anyway, the point is, make sure that you DO have high quality RAM when overclocking because it makes a huge difference.