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PCI/AGP and PCI latency

651 views 4 replies 3 participants last post by  *ka24e* 
#1 ·
I know you would want to keep the PCI/AGP ratio at 66.6/33.3, and running it higher may effect stability and what not.

Would raising PCI latency (stock = 32) help keep a higher PCI/AGP ratio stable?
For example, if I had the PCI/AGP ratio (no lock on this board, Abit VT7 btw) at 80/40, would adjusting the PCI latency help at all with stability, or would it make no difference?
 
#2 ·
It shouldn't make any difference. As a side note I've seen only one use for the PCI latency setting and that was to change it to 128 to remove some crackling noise from the sound card.
Depending on the CPU you have you may be better off just OCing up to the next speed bin, for example fsb 133 to 166 as that setting will reset the PCI clock back to 33MHz.
 
#3 ·
Thank you for your reply.

That's what I figured, but I couldn't seem to find a straight answer. This board has an AGP/PCI lock so to speak. Basically it uses a 3:2:1 - 6:2:1 divider to calculate the speeds.
Its running a 200fsb 3.0E P4 and any overclocking results in overclocking the AGP/PCI bus, and it doesn't seem to work after a 76/38 ratio.

Thanks again for your help.
 
#4 ·
It's unlikely that changing PCI latency will improve the stability of out of spec AGP/PCI speeds.

If you can manually adjust your reference clock/agp/pci ratio use a ratio that will keep AGP/PCI speeds at or below 66.7/33.3MHz. You will lose very little performance from running a below stock AGP/PCI speed.

If 6:2:1 is the highest ratio, you are out of luck with that chip/board combination. You'd either need a CPU with a lower stock FSB or a higher multiplier.
 
#5 ·
I can say that the system feels overall quicker or snappier running with the AGP/PCI ratio closer to 66/33. The system will run stable at 3.5ghz (1:1 Ram @ 468mhz) at like 78/39, but it just feels sluggish up there.

Right now its running at 3.4 ghz, 1:1 ratio, ram @ 454mhz @ 3-3-3-6 1T and the video card (EAH3450 AGP) is running at 725 Gpu / 550 Mem rock solid. That's on stock CPU vcore with Abit/Asus's classic vdrop, lol. The chip defiantly has potential, but the board sucks very bad.
 
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