Dealing with busses that can't be locked

baldurga

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Hi to everybody!

I'm overclocking my 8KHA+ mobo (KT266A). Currently I have a XP1700+, 512Mb Corsair PC3200 (1 stick), GF3Ti500.

I have bought the new memory to be sure it can support any frecuency I can set. I want to overclock as much as I can, but I have concerns of running PCI, AGP and HD out of spec. How can I mitigate the overclock?

I have ideas that I don't know if can help:

- <b>AGP</b>: instead of running AGP x4, running at AGP x2. That implies that I can overclock the bus up to x2 due it is running at half the teoretical speed? In other words:

bus x2 (due to overclocked bus) x 2 (AGP) = bus x1 (no overclock) x 4 (AGP)

Something is telling me it sound too good to be true ...

- <b>Hard Disc</b>: again, running with an ATA below its maximum could compensate the overclocking. I don't know the exact maths, but would be similar to the AGP case. Let's say running on ATA66 instead of ATA100 gives me a 33% of safe bus overclock.

Please tell me what is wrong on my ideas as well as any other ways to mitigate the overclock on the other components. Thanks a lot in advance!


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pIII_Man

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are you having instabilities?

If not then you are fine...

The geforce3 should go pretty far without any problems my guess is around 95-100mhz agp bus

everything you are saying about the agp bus is wrong...agp 4x mearly means it is a 256 bit bus, while agp 2x was a 128 bit bus, both physically run at 66.66 mhz.

Most modern hard drives can go pretty far..i would be willing to say around 42mhz, so if anything your cpu or chipset are probably holding you back. The only way to get slightly better overclocks is to increase the chipset voltage and/or the agp signaling voltage.


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Crashman

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Wrong, AGP2x is 32-bit, AGP4x is 32-bit, AGP8x is 32-bit. As far as I know, AGP2x uses a DDR bus, 4x a QDR bus, and 8x an ODR bus.

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baldurga

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Well, in both cases seems that my logic for the AGP is not right ... ok.

Here is what I have right now:

- From 135Mhz, I increased 5Mhz each time. Until 160Mhz everything seemed right. I went into Windows with no problem.
- At 165Mhz, the computer simply stoped when it's time to recognize the drives (HD and DVD).
- One shot at 170Mhz, to see if the 1/5 divider exist and would solved everything. Well, at least that's not my case, computer freezed at the same step as before. But this time I wasn't able to get into BIOS settings (glups!). I didn't try anymore, was affraid I was "frying something".
- I was finally able to solve the problem be leaving the computer for some hours, then start again and go into BIOS as quick as possible.

I am not sure, but my guess is that because recognising the drives was the problem, I should do something to reduce the overclock on that side. Also, based on your comments, 165Mhz is almost a 25% overclock. That leave the AGP bus at 82.5Mhz (GF3 should support) but the HD at 41.25Mhz, quite close to the 42Mhz (and every HD is different). That would reinforce my idea that HD could be the problem (note: I suppose the DVD has NO function when computer starts other than being recognized)

The chipset was another factor, but I know other KT266A mobos are not actively cooled, so I suppose this is not the issue in this case.

Well, that's all I have. Any help would be appreciated and any question answered. Thanks again!


Still looking for a <b>good online retailer</b> in Spain :frown:
 

psykoikonov

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Careful of anything over 40MHz on PCI bus speed. You can destroy your mobo's hdd controller (as well as corrupt files on your hdd). I know from experience that anything over 38Mhz and my WD JB's start messing up bad. At 39MHz every files read from the hdd in the OS is said to be corrupt!!

Psyko

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baldurga

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That sound horrible ... downgradeing ATA (like using ATA66 instead of ATA100) helps you in any way? Sorry, first of all, have you try it? Do you know of any experience?



Still looking for a <b>good online retailer</b> in Spain :frown:
 

phsstpok

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The AGP bus is 32 bits wide, period.

Crashman didn't say anything about bandwidth but it is a related subject. (I'm sure he can explain it better but here goes).

AGP is currently specified to run 66 Mhz.

The AGP bus is 32 bits wide.

AGP 1X means that data is sent once per clock. That is, 32 bits of data are transfered on each clock pulse.

AGP 2X is a DDR technology (double data rate). Data is transfered TWICE per clock (once on the leading edge of the clock pulse and once on the trailing edge). Only 32 bits of data are transfered at a time but it's done twice each pulse.

Similary for AGP 4x and AGP 8X data is transfered four times for each clock pulse and eight times for each clock pulse, repectively.

As the AGP designations imply, the theoretical bandwith doubles from AGP 1X to AGP 2X and doubles from 2X to 4X and again on to 8X because the number of transfers per clock pulse doubles each time. The bus width and bus frequency are held constant.

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pIII_Man

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okay now heres the big question...i am obviously wrong in this statement so please tell my why...

ok...when you have a 32 bit bus (agp) then you double pump it, dont you get a bus that is effectivly 64 bits?

Therefore why can't i call a 2x agp bus a 64 bit bus?


If it isn't a P6 then it isn't a procesor
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phsstpok

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Bus width is a physical property. 32 of the pins on an AGP connector are the data pins representing the 32 bits of data.





<b>56K, slow and steady does not win the race on internet!</b>
 

Crashman

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It's NOT the same idea as Dual Channel memory, which doubles the number of data pins by using two DIMMs...

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pIII_Man

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ok i think i got it...agp 2x would transmit 2 packets of data per clock cycle? 4x would transmit 4 packets per cycle etc.?

However doesnt this effectivly make a 64/128/256 bit bus? Thats the part i dont understand...if it transmits 64 bits per clock cycle can't it be labled as a 64 bit bus?


If it isn't a P6 then it isn't a procesor
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phsstpok

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The internal registers/buffers for AGP are still 32-bit devices. This is why the bus isn't 64-bit/128-bit/256-bit. The data is handled 32 bits at a time. It may be up to 8 times per clock pulse but still only 32 bits at a time.

<b>56K, slow and steady does not win the race on internet!</b>