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AGP Bus frequency?

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alinosa

Member
Joined
Feb 18, 2002
Location
San Antonio, TX
how much benefit is there to upping this setting in the bios? is there a limit to how high i should push it? my dfi lets me adjust this freq seperately from my fsb. i read that the pci bus should not exceed 38 MHz, so the AGP being twice that... should i not go over 76MHz? any help would be great.

allen
 

zabs

Registered
Joined
May 21, 2004
Quick question. Is there anything that can improve stability on an overclocked AGP bus? Better cooling?

The reason I ask is that I am working on OC'ing dual mobile XP 2600's on a Gigabyte MB.

I have the multiplier setup for 17x (because the voltage required to pull off 18x produces too much heat for my cpu coolers at the moment.) So I was running 17x @ 140 (2380Mhz.) This runs the pci bus at 38Mhz.

My FX 5600 is fine until I attempts to play Enemey Territory (or possibly other 3d games, ET just happens to be the only one I'm into at the moment,) and then performance is choppy, and the textures flash funny and do crazy things, sometimes even eventually locking up.

I've tried reducing the FSB overclock, but it seems ANYTHING over stock 133/33 causes problems.

Anybody have any ideas as to what I can do?
I had eventully hoped for 2446 by running 17x @ 144/40 but now it doesn't seem obtainable.
 

repo man11

Member
Joined
Dec 28, 2001
I doubt it is the AGP bus specifically that is causing your problem. I think it is more likely general instability, and the load from the game brings it to the surface.

In my opinion, your best bet for running the higher FSB speeds lies in better cooling for your northbridge. Have you pulled your northbridge HSF off to check and see if it has any thermal compound?

Improving the northbridge cooling allowed me to greatly increase the FSB on my old 8K3A+. Check my signature.

High system temps can cause strange symptoms as well, as the card, and even the MOSFETs and other mainboard components overheat. If it is in the 90's in here (Fahrenheit, happens often in the summer) and my case temp gets up to around 40C, I'll start to see strange flashes in games.
 

zabs

Registered
Joined
May 21, 2004
Thank you for the advice.

The northbride on my revision of the Gigabyte motherboard comes actively cooled by the manufacturer and seems to do a good job, but I do intend to replace the stock HSF with a Zalman heatsink, so perhaps this will yield some better results.

I have done extensive load testing using distributed net and several other burn in programs without any real issue. I have also run Memtest86 for several days without any errors in the memory (as I only have registered, ecc, pc2100 memory and was worried with the custom timings and increased FSB there would be problems.)

The whole system is currently on it's side with the case open (mostly for easy acces but having the side effect of allowing all heat to vent upward right out of the case) and is located in my basement where it is nice and chilly.
 

repo man11

Member
Joined
Dec 28, 2001
My old KT7A had an HSF on the northbridge, but when I pulled it off, it barely had a dot of thermal grease; and that was dried to a powder. I lapped it, and used some AS3 when I remounted it. Afterwards I was able to run it to a little over 150 MHz FSB until bad caps killed it.

I wasn't able to get much over 175 with my 8K3A+ until I replaced the cheapy aluminum heatsink with one with a fan, and some good thermal grease. I think the stock one insulated the chip more than anything.
 
OP
alinosa

alinosa

Member
Joined
Feb 18, 2002
Location
San Antonio, TX
i have a dfi mobo (see sig) and it has a monstrous heatsink on the NB, i have fan in my window that blows air semi-over it (like a third of the fan is above my vid card and therefore blowing on the NB) should i try to get more cooling on it? i hit 217 MHz with my current setup. My memory is keeping me from hitting anything over 217, btw...
 

pantner

Member
Joined
Jul 18, 2004
I run a Mercury KNU400X-L (which i just found out is a re-badged Epox) and i can hit 230, when i get to 232 or above it will not run very well....mine just has a passive Copper HeatSink on it (both north&south bridge) which get VERY hot, but it seems to do the job..
 

Highlander

Member
Joined
Jul 29, 2002
Location
UK
Radeons wont go above ~ 75 mhz AGP frequency (9800pro crapped out at 76. with 1.7vAGP) BUT the Nvidias just keep on climbing, benched me 4200 @ 90mhz agp no problems, gives a small boost in 01, its not massive but its there :) above 90 and the card gets a little flakey, might try again at 95 next session and see if it'll stabilise there with vmods :)