I have tested the same drivers with one of our laptops featuring Intel® HD Graphics 3000 (processor i7-2820QM) and there is no performance decrease.
The results on the Windows System Assessment Tool running the Formal Assessment through the command prompt shows:
Direct3D Geometry Performance 171.74 F/s with latest driver 169.26 F/s (with previous version) Direct3D Geometry Performance 121.84 F/s with latest driver 120.09 F/s (with previous version)
The latest version tested is 126.96.36.1999 and the previous version used is 188.8.131.521
The summarized WEI results are:
In this particular case, I suggest you to check directly with your computer manufacturer to obtain a customized driver for your system if you continue to have performance problems when using the generic drivers on our site.
Unfortuantely, those are not the kinds of results that I see. Both computers are self-built desktops, so there are no specialized drivers.
Just to make sure there wasn't some misconfiguration in the software or drivers, I just tested this again with fresh installs of Windows 7 SP1 x64 on spare partitions, installed the drivers using the installer, and made no changes of any kind to the driver settings, and I'm still seeing these drops in benchmarks between the driver versions.
I guess the big difference that I see here is that I am using a "6EU" processor. Here are my two machines:
* Board manufacturer: Gigabyte
* Chipset: H67
* CPU: i5-2400
* Board manufacturer: Zotac
* Chipset: H67
* CPU: Pentium G620T
Both machines run Windows 7 SP1 x64. Both machines exhibited the same performance discrepancy (even the same amount of drop) between the April and September drivers.
As you know, both the i5-2400 and G620T contain the lower-end graphics with only half the GPU execution units; maybe this is something that affects only those GPUs? Or maybe it's something that only affects desktop Sandy Bridge and not mobile SB?