Overclocking a 4870

[reznik]

i got new setup and was thining of Oc ing my GFX card:

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Q6600 @ 3.2ghz 1.35v (37 idle 60 100% load) (8 x 400 fsb)
4gb corsair xms 2 pc 6400
Asus Rampage Formula
His Radeon formula 4870 @ 35% fan
western digital 500gb sata 2 @ 7200rpm
OCZ GameXtreme 600w
19 inch AMW lcd monitor
Vista home premium 64bit

As you know default clock speeds for the card is: 750/900
i wanted to boost it to 780-790/1000-1100

should i increase my pci e frequency > 100 maybe to 110?

how safe is it to increase my pci and to what value?

i know i have a sata but if i keep it to safe values should it be ok?

[Super Nade]

Go for it. At this point you are limited by ATi's Catalyst Control Center.

[vixro]

is that a 60c load I see with only 1.35v from a 37c idle on your q6600? Ouch. :(

Keep in mind that it would probably be a good idea to turn up the fan speed on your 4870 before messing with it, as the temperatures are quite high already.

[reznik]

i know...i dont understand that massive quad temp increase thats the only thing stopping me from pumping that cpu to 3.6 which it easily boots to but temps get to around 71 load :( as for the gfx card..could someone possible give a proper answer about the pci and how safe it is?

[vixro]

Overclocking a GPU is as safe/unsafe as overclocking a CPU. If it fails it will just crash and reboot back to normal speeds. Since CCC limits how high it can really go right now anyway, it's going to be relatively safe.

[reznik]

i mean i read somewhere in order to achieve a more stable oc of the gfx card i shoudl increase my pci e bus speed then change the clocks on teh card itself? but i want to know if changing the pci speed is entirely safe and if so to what degree considering i have a sata drive?

[WorshipMe]

Don't increase the PCI-E bus speed. Increasing that is basically increasing the clock speeds of the GPU, a hardware site tested this and found that they were able to achieve a higher overclock by leaving the PCI-E bus at 100 and increasing the clock speeds using a Windows based app.

[reznik]

BOO HOO :( i jaked it up to 780/1000 in ccc temps were about 70 max which is fine but when i ran ati tool after 7 seconds it detected errors? wtf i returned it bak to stock np found

[rdrash]

Don't increase the PCI-E bus speed. Increasing that is basically increasing the clock speeds of the GPU, a hardware site tested this and found that they were able to achieve a higher overclock by leaving the PCI-E bus at 100 and increasing the clock speeds using a Windows based app.

What site, can you provide a link? I ask because it is a fairly common practice amongst the people I hang with here to push the PCI-E bus speed as high as possible...generally it improves scores in our games by quite abit. :beer:

[WorshipMe]

I know I was searching for a 9800GTX review at the time. I'll try and find it again...

EDIT: Here is something: http://www.overclockersclub.com/reviews/xfx_9800gtx/5.htm

Although I was absolutely sure I read that the GPU clock speed increases with the PCI-E speed...

RE-EDIT: This is where I got it from: http://www.techpowerup.com/reviews/NVIDIA/Shady_9600_GT/2.html

[Farinorco]

Don't increase the PCI-E bus speed. Increasing that is basically increasing the clock speeds of the GPU, a hardware site tested this and found that they were able to achieve a higher overclock by leaving the PCI-E bus at 100 and increasing the clock speeds using a Windows based app.

Are you sure about that? I've always thought that increasing the PCI-E frequency makes the communication through the port faster, increasing the data bandwidth, but has nothing to do with the devices connected to it and its working frequencies.

Except of course in the case of GeForce 9600 and 9800 (and maybe other NVIDIA G92 cards, but I don't have any proof about it). Those cards base their clock frequency on a PCI-E freq derived base instead of a fixed base (usually the clocks are based over a fixed base, lets say 25MHz, that's why when overclocking graphic cards usually you only have performance increases in multiples of a given number). The "fixed" base of GF 9xxx is the PCI-E frequency /4, so if you have 100MHz, the base is 25MHz, but if you have 108MHz, the base is 27MHz. This way, if you overclock the PCI-E with those cards, you are effectively overclocking the GPU also. But this isn't a general rule, is a specific technology of those GF 9xxx cards.

It may sound like a little stupid thing, but then is when you learn that certain nForce based mobos (since certain chipset, I don't know which one), when in 3D mode, do a dynamic overclock of the PCI-E ports to 108MHz, effectively doing a transparent and "stealth" overclock of the card, and artificially inflating the results get (because you're actually overclocking the card and you're not telling that you're doing so...)

He. I suppose that those people at NVIDIA marketing department are true genious. Twisted and kind of dishonest, but genious after all. Of course, I tend to not trust reviews done on a NVIDIA chipset mobo since I know this...

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EDIT: Ah, almost forgot it... by now people is using RBE (Radeon Bios Editor) to overclock the cards past the CCC limits. Of course, that implies to edit the bios and flash the new one, and disable CCC Overdrive. The last version of RBE seems to recognize each one of the 6-8 (dunno remember exactly how many of them there are) different Power Play profiles with core clocks, mem clocks, voltages (though changing them doesn't have any effect except in the 4850 that can be changed up to 1.21 vcore), a complex programmable fan behaviour profile and so. At least in the 4850, I suppose that the 4870 too.

It has been used to overclock overvolted 4850 up to 900-950 MHz core, hehe...