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graphics bus relationship to system

Last response: in Graphics & Displays
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April 30, 2007 1:56:07 AM

what is "effective speed" for a graphics card? is it a cryptic puzzle like fsb to ram to cpu speed, or something similar? such as, in nTune i bump up my 8800gts 640mb from 513 mhz core and 712 mhz memory to 650/1050 respectively. could someone explain to me what the relationship is between graphics bus and fsb or memory bus. (I do understand the fsb:ram, and the efffect of fsb being quad-pumped to give 1066 or 1333, and the multiplier effect on such to determine true cpu clock speed.) just need the info to understand the graphics interaction.
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thanks a jillion
April 30, 2007 6:42:42 AM

Well, when you increase the core and memory speed for your video card, your just increasing how fast the card is operating, not how fast the card talks to the computer.

The card talks to the computer through the pci express bus, which is made up of up to 16 "lanes" which are dedicated channels connected straight to the northbridge, which connects to the cpu. The lanes usually operate at 100mhz, but it can be raised in the bios of some motherboards. I don't recommend overclocking this connection as the instability it can cause is not worth the small performace boast.

Here,s a little info about pci express if your interested

http://www.hardwaresecrets.com/article/190/2
http://en.wikipedia.org/wiki/PCIE
a c 176 U Graphics card
April 30, 2007 7:17:10 AM

The only effective speed that I know of involving graphic cards is the memory. Like DDR, you need to double it to get the effective/real speed. 700MHz DDR ram (doesn't matter if its system ram or video ram) will operate at 1.4GHz effective speed.

The graphics bus since the days for the NF2/KT880 have been lockable. You don't normally want to increase it, as it causes problems. (hense the reason why people want chipset that lock the AGP/PCIe/PCI bus.)
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April 30, 2007 7:38:24 AM

i hope i don't repeat something already explained but what fsb speed does a gpu have?
a c 176 U Graphics card
April 30, 2007 8:07:41 AM

I don't understand the question. The FSB is the bus the CPU uses to talk to the northbridge. The FSB has nothing to do with the GPU.
a c 176 U Graphics card
April 30, 2007 8:33:49 AM

Quote:
the GPU doesnt have a FSB
it uses the FSB on the motherboard and runs at what ever speed the FSB is setup to run on the motherboard


Huh B&C? It either doesn't have an FSB, or it uses the one on the motherboard, it can't be both. Again, the FSB is the bus used by the CPU to talk to the northbridge. No other device uses the FSB. All expansion cards use whatever bus they are plugged into. It might be the PCI bus, or the AGP bus, or the PCIe bus, but it is NOT the FSB.
a c 176 U Graphics card
April 30, 2007 8:59:56 AM

LOL, try being called 47 all the time...

I bolded the words to show how what you wrote can't be true. If it doesn't have a FSB, then it can't use the FSB to communicate. Your second post is correct. (I guess old hands like me still call it the northbridge instead of the MCH.)
May 1, 2007 12:46:43 AM

thats it. just what i needed. it does help my 3d mark 06 from 8650 go to 10988. cpu and ram stay at stock. the setting my question was over was the PCI-E freq. in my bios at 100mhz. i don't want to touch that, right. just the ntune optimal oc for this card works great. thanks for the info everyone!
mpilchfamily is the bomb, 2.
btw, here's the specs

C2D E6600
2gb dual channel Mushkin DDR2800 @4-4-4-12
msi p6nsli platinum mobo
evga 8800gts 640mb
coolermaster hyper tx cpu cooler(24c-27c idle!)
antec case
Ultra xfinity 600w sli edition PSU
360 Gb SATA2 wd hdd
a c 176 U Graphics card
May 1, 2007 4:49:48 AM

Oh sure, I guess I'm just chopped liver...

Yes, you want to keep the PCIe frequency at 100MHz. I've seen some poeple get better results if they overclock it to 107MHz. I've never heard of anything good happening if you go to 110MHz. I'd just keep it at 100MHz.
May 1, 2007 5:01:27 AM

sorry 4745454b, mpilch has been a help once before, when i was merely spec'ing the successor to my PC throne. but now, a special thanks to you as well, for all your much sought after knowledge.....

thanks everyone, for all the help.
May 2, 2007 9:58:14 AM

ok let's say that the gpu doesn't ave a fsb. still it has to communicate with the graphics card's memory. i whant to know what is the speed used by the gpu to communicate ot the memory
May 2, 2007 6:13:55 PM

take the 8800 : gpu clock 625Mhz mem clock 900Mhz (1800Mhz effective)
if the gpu speed is a multiple of a base speed than for sure that base speed is lower than the memory's real speed (900Mhz). i think this means that the gpu can't use the full speed of the memory. correct me if i'm wrong and please try to explain a little bit in detail what your pinion is.
!