Vid overclocking AGP 4x vs 8x

[LeeJend]

This question gets a little complicated...

Having seen multiple fried vid cards I now recommend against overclocking them, BUT...

I was just reading the posts on running the barton 333 with my MB (giga 7VRXP http://mysite.freeserve.com/hoodspages/fifth_divider.htm) and the gyrations required to get the 7VRXP to run with a Barton at 333 got me thinking.

Basically with the VRXP you end up with 2xFSB as the AGP speed which, when trying to run a Barton at 333 FSB, means the AGP clock goes to 333 also. But, since I have the 8X AGP Radeon 9500 PRO it can handle higher than the 4x AGP = 266 mhz. This would appear to not be overclocking the Vid Card?

The questions:

Will there be other effects on the AGP interface timing even though clock is in spec for 8x?

Are the Video "on board" mem and GPU clocks independent of the AGP clock? It looks like yes from what I can tell.

I have some 333 memory so if I OC the MB to a Barton FSB I can run synchronous at 333 (mem, fsb, vid). This has some interesting possibilities for a peformance boost by just going to a $95 Barton XP 2500 (even before overclcoking the multiplier).

Anybody see any loopholes in this?

I'd add a fan to the chipset cooler as a precaution. Old Vid card coolers (courtesy of the above mentioned fried vid cards) and a piece of double sided heat sink tape work nicely.

 

[Sazar]

PLEASE READ LEEJEND

Originally posted by LeeJend
This question gets a little complicated...

Having seen multiple fried vid cards I now recommend against overclocking them, BUT...

I was just reading the posts on running the barton 333 with my MB (giga 7VRXP http://mysite.freeserve.com/hoodspages/fifth_divider.htm) and the gyrations required to get the 7VRXP to run with a Barton at 333 got me thinking.

Basically with the VRXP you end up with 2xFSB as the AGP speed which, when trying to run a Barton at 333 FSB, means the AGP clock goes to 333 also. But, since I have the 8X AGP Radeon 9500 PRO it can handle higher than the 4x AGP = 266 mhz. This would appear to not be overclocking the Vid Card?

The questions:

Will there be other effects on the AGP interface timing even though clock is in spec for 8x?

Are the Video "on board" mem and GPU clocks independent of the AGP clock? It looks like yes from what I can tell.

I have some 333 memory so if I OC the MB to a Barton FSB I can run synchronous at 333 (mem, fsb, vid). This has some interesting possibilities for a peformance boost by just going to a $95 Barton XP 2500 (even before overclcoking the multiplier).

Anybody see any loopholes in this?

I'd add a fan to the chipset cooler as a precaution. Old Vid card coolers (courtesy of the above mentioned fried vid cards) and a piece of double sided heat sink tape work nicely.

I have a feeling you are incorrectly assessing the situation...

the agp port operates @ a frequency of 66mhz...

the 2x/4x/8x and what not designations denote bandwidth...

if you are overclocking your fsb it is always recommended to keep a locked divider ie ratio of 1/1 or 2/3 or whatever to ensure that the agp port is running @ the proper frequency... ie 66mhz..

if you oc and you do not have a locked multiplier you are going to effectively overclock your agp port... and this is not all that good for the video card...

the agp port is designed to work within specifications... therefore I highly recommend you do a little more reading into agp ports and what they are and how the work before considering the overclock you are looking into...

an frequency of 70-75 mhz is probably the maximum you should consider for your agp port... if you really have to overclock your rig and have no locked multiplier...

 

[jumpy]

Sazar is right with that LeeJend. I've had my agp port running at 80mhz before but I wouldnt recommend doing this for long periods of time. Different cards each have their own threshold. Sometimes though, a higher agp frequency has been known to allow a higher overclock of the card and/or more stability in an overclock. We're not talking about thrashing the frequency to 80mhz, but slight adjustments have worked in many instances. AFAIK the agp speed (2x, 4x etc) has no effect at all on the overclock ability of a card.

 

[LeeJend]

Thanks guys. I thought it sounded too much like getting something for nothing. I swore off frying video cards for my New Years resolution.

I'll stick with the Palomino for now.