FSB:AGP ratio?

[SkyMunky]

I'm going to try (newbie) to o/c a PIII450 on a AbitBE6 mobo. When I crank up the FSP to 112 or 124 or however high I can get it, do I need to turn down the AGP ratio somehow in BIOS so that I don't fry my TNT2Ultra card? Any help would be appreciated before I undertake the task. (None of the "Overclocking Step-by-Step's" seem to address this). Thanks...

[Roy]

Yes. Run the ratio at 2/3. This gives 66 AGP for 100 FSB. etc. Some AGP cards will take full FSB speed, but start out slow. Change it up after everything is maxed out.

[SkyMunky]

Thanks very much. I suppose then my next question is: Do "overclocking tools" which come with vendor's TNT2Ultra cards (Diamond's in my case) take into account the freq. of the AGP slot? In other words, if I'm running at the default 150 (is that Diamond's default) core speed for the TNT2ultra card in the AGP slot, is it *really* 150 if the AGP ratio has been turned down to 2/3? [did that make sense?] Thanks again...

[AuraEdge]

I think the speeds on the diamond card (150/175) run independently of the FBS (2/3 x 100 = 66)
I dont really understand the coverclocking of the AGP bus at all aside from the fact that you could fry it..I have my AGP bus at 124 x 2/3 right now..no problems really..I dont think you seriously hit any problems til you hit 100FBS on the AGP...But dont take my word on it

[Roy]

socalgal might give you a better answer. I think she has a 770 Ultra / PIII450 @ 504 - 2/3 AGP. I think my previous thoughts are safe. Maybe your experimentation will enlighten all of us. It sounds like you won't fry it.

[This message has been edited by Roy (edited 07-12-99).]

[SkyMunky]

I should be getting the rest of my hardware in Wed (7/14/99), so I'll let you know what I find out tinkering with it. Thanks for all the input!

[socalgal]

The V770 is 150/183 at default. I o'c the card at Boost Level 3 for games, using InControls 99.
Also, my PIII 450 @504, keeping the AGPCLK/CPUCLK at 2/3. Can't give you technical response why, but there is one, and 1/1 is not the way to go.

[This message has been edited by socalgal (edited 07-13-99).]

[BBA]

Hi socalgal! Haven't heard much from ya lately.

I'm the man who can tell you about OC and crispy TNT2 ULTRA's!

Do not whatever you do (unless you just want to go to the return counter with your TNT2) run AGP/FSB at 1/1 with anything 100Mhz or over! Especially not 124Mhz!

I tried to see if the card would handle it, and the moment I turned the PC on, a flash was all I saw!

I had a hard time OC'ing the CPU again after that also, but an eventual BIOS flash brought the MB back in line.

The moral of the story is: Keep the AGP/FSB at 2/3.


BBA


[This message has been edited by BBA (edited 07-13-99).]

[KillerBug]

I have a voodoo banshee based card, it does 83mhz at 1/1, but I have to turn it down to 2/3 at 100, 112, and 124mhz. I think it sets itself to defaults on every power on or reset, as I have an overclocking/underclocking tool and it does not just make the adjustment, it has to add stuff to autoexec.bat and config.sys but then the TNT2 ultra is very different and may well use a different power-on design.

[socalgal]

Hi BBA ~ been busy...

Your post on the 1/1 death-cause of your vidcard was one of the good pieces of advice I received to "not do that" http://www.sysopt.com/forum/smile.gif

[This message has been edited by socalgal (edited 07-13-99).]

[macian]

In a similar vein, I am in the process of assembling a new box with a Viper 550 video card, a Celeron 366 CPU and an Abit ZM6 or BH6 board. My understanding is that you can crank the FSB speed down by half at 66Mhz to get 33Mhz speed on the AGP bus or by 1/3 at 100Mhz again to get 33Mhz on the AGP bus. If I cannot overclock the Celeron to 100Mhz and use the 1/2 multiplier I will overclock the video card, alternatively I could use the 1/3 factor and "underclock" the card. My question is "Is overclocking the video card a worry and what can I do to be reasonably confident that I won't fry the card?"

[SkyMunky]

I guess another question would be: What about the FSB:PCI ratio? Any thoughts?

[AuraEdge]

PCI should be as close to 33
AGP should be as close to 66 as it can be
If you have a PIII 450 AGP should already be on 2/3 and PCI on 1/3, and you should prolly not hafta set it, You might wanna set PCI on 1/4 instead if you have that option..I have my FSB at 124, AGP at 2/3 (83) and PCI at 1/4 (31)

[macian]

How far above 66Mhz can you go with a TNT card before you run the risk of damage? Do things not work and can be started again after cooling off or is flash puff and off to buy a new video card? Clearly 100 FSB and a 1/1 ratio is not appropriate from comments above.