One of the more interesting comparisons to be drawn is the one between the 8500 GT and the overclocked 8500 GT card, which outperforms the reference clocked 8500 GT Zone edition by more than 25%. Both cards are closely priced, and you can overclock your Zone edition to match the AMP's performance. The AMP version's core is clocked at 700MHz, which isn't impossible to reach with your passive Zone edition card. If you want to try this, under no circumstances should you forget to provide the Zone card with a great case airflow.
We overclocked the 8500 GT Zone to 700MHz core, and 426/852MHz memory. This got us very similar performance as with the 8500 GT AMP card. Due to the faster memory clock, the 3Dmark06 score was a bit higher. Considering it's a passive card, we recommend that you stick to the reference clocks, which should be enough for the average user. The card won't heat up too much and its lifespan will probably be longer too.
The G84 Geforce 8600 GT has 32 stream processors, 8 ROPs, 16 texture filtering units and texture addressing units, which is twice as much as on G86 Geforce 8500 GT or 8400 GS cards which have 16 stream processors, 4 ROPs, 8 texture filtering units and texture addressing units. On top of that, GDDR3 memory on the 8600 GT cards gets you a significant performance boost over the cheaper G86 based cards.
As far as the 8600 GT Zone edition goes, we managed to get the core up to 674MHz, stable. Zotac uses Hynix mHY5RS123235 FP-14 GDDR3 memory on these cards. Rated at 1.4ns, we were able to overclock the memory to 735/1470MHz.