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After some testing, the best points on the core clock of the nVidia 7800 series cards are whole multiples of the core frequency oscillation of 27 MHz. That calculates to the following root core clocks:
(17 x 27) - 40 = 419
(18 x 27) - 40 = 446
(19 x 27) - 40 = 473
(20 x 27) - 40 = 500
(21 x 27) - 40 = 527
(22 x 27) - 40 = 554
(23 x 27) - 40 = 581
And, here is how a single MHz below the whole number threshold affects 3Dmark05 scores:
445 8052
446 8222
472 8404
473 8508
499 8669
500 8753
Now, what about the other two cores. How are those controlled?
Well, when you adjust the root clock, you actually adjust all three clocks.
The root clock gets bumped by 40 MHz to represent the real geometry or vertex core clock. So, lets pick 450 core, which so many vendors use. 486 is the best vertex clock value (18*27), which translates to 446 root (486-40). So, we would actually have 490 using a 450 root clock, a 4 Mhz pad on the required frequency.
But, the shader and ROP cores start at 415 (really 418.5) in low power, and jump in whole frequency values (ie, 17 x 27 = 459) to a value that is less than13.5 Ghz from the closest whole value to the root frequency. In this case the root frequency is 450. So, this limits the other two cores to (17 x 27 ) 459, since 450 is 9 MHz less than 459 but 18 MHz over 432 (16 x 27).
So, a little confusing, but you do have some control over the other two clocks.
So, here is a list of primary - vertex based (red) and secondary - ROP and shader based (yellow) root clock OC targets. The red will yield the larger gain, and you will see a second, albeit smaller gain on the blue clocks where the GOP/Shader clock is the same as the root clock.
419
432 - the nVidia spec root clock
446 - so many vendors use 450
459 - why BFG uses 460
473
486 - why eVGA, XFX, and BFG use 490 on limited cards
500
513
527
540 - How I got 9512 on 3DMark05 with a lowly 3200+ and one 7800 GTX
554
567
581
594
608
621
Here is an example of the clustering of the results before and after the secondary clock:
484 - 8465
485 - 8464
486 - 8482
487 - 8485
488 - 8489
So, still a bit of linear growth, but a small bump at the right frequency.
A sample of the clocks for 579, with the root clock at 530 (ASUS TOP BIOS has a 50 MHz bump).
(17 x 27) - 40 = 419
(18 x 27) - 40 = 446
(19 x 27) - 40 = 473
(20 x 27) - 40 = 500
(21 x 27) - 40 = 527
(22 x 27) - 40 = 554
(23 x 27) - 40 = 581
And, here is how a single MHz below the whole number threshold affects 3Dmark05 scores:
445 8052
446 8222
472 8404
473 8508
499 8669
500 8753
Now, what about the other two cores. How are those controlled?
Well, when you adjust the root clock, you actually adjust all three clocks.
The root clock gets bumped by 40 MHz to represent the real geometry or vertex core clock. So, lets pick 450 core, which so many vendors use. 486 is the best vertex clock value (18*27), which translates to 446 root (486-40). So, we would actually have 490 using a 450 root clock, a 4 Mhz pad on the required frequency.
But, the shader and ROP cores start at 415 (really 418.5) in low power, and jump in whole frequency values (ie, 17 x 27 = 459) to a value that is less than13.5 Ghz from the closest whole value to the root frequency. In this case the root frequency is 450. So, this limits the other two cores to (17 x 27 ) 459, since 450 is 9 MHz less than 459 but 18 MHz over 432 (16 x 27).
So, a little confusing, but you do have some control over the other two clocks.
So, here is a list of primary - vertex based (red) and secondary - ROP and shader based (yellow) root clock OC targets. The red will yield the larger gain, and you will see a second, albeit smaller gain on the blue clocks where the GOP/Shader clock is the same as the root clock.
419
432 - the nVidia spec root clock
446 - so many vendors use 450
459 - why BFG uses 460
473
486 - why eVGA, XFX, and BFG use 490 on limited cards
500
513
527
540 - How I got 9512 on 3DMark05 with a lowly 3200+ and one 7800 GTX
554
567
581
594
608
621
Here is an example of the clustering of the results before and after the secondary clock:
484 - 8465
485 - 8464
486 - 8482
487 - 8485
488 - 8489
So, still a bit of linear growth, but a small bump at the right frequency.
A sample of the clocks for 579, with the root clock at 530 (ASUS TOP BIOS has a 50 MHz bump).