Calculating the key OC points on the 7800

[HeavyH20]

I have seen some people using a custom BIOS with no delta so the clocks can be locked instead of dealing with the delta. While this sounds promising, you have to wonder why nVidia chose to use a delta. So, I ran some benchmarks to discover which is really better. In addition to the regular 40 delta, I also wondered how effective the ASUS TOP card was with a 50 Mhz delta, so I created a BIOS with that delta as well.

Here are the results of the delta scaling on a 7800 GTX.

Test System:
AMD 64 3200+ @ 2.5 GHz
MSI K8N Diamond
DDR 3200 2.5-3-3-7, 1T

Settings:
all driver settings default quality, 81.82

3DMark05 results

Clock____0 Delta_______40 Delta_______50 Delta
490_______8347_________8570__________8593
495_______8397_________8588__________8603
500_______8451_________8728__________8772
505_______8475_________8764__________8781
510_______8534_________8769__________8823
513_______8569_________8803__________8847
520_______8577_________8805__________8864
525_______8703_________8852__________8921
527_______8710_________8912__________8980
530_______8728_________8935__________9045
535_______8765_________8983__________9078
540_______8824_________9034__________9123


Summary

The zero delta BIOS inhibits performance, clock for clock. Additionally, the OC limits are not increased with no delta in place.

The best delta value appears not be 40, or none, but 50.