How did you get the 20% fsb overclock? I have only done 33% overclock via PLL hardmod. On the inspiron 8600 I can't get any software overclocking tool to read the clock generator. It would be great if I could add fine grain overclocking on top of the 33%. I have a respectable 745 CPU that does 2.4 GHz at 1.33V. Also it looks like your CPU throttled. There seems to be a hidden CPU power limit on the i8600 series that you need to disable with RMclock. I get 1K CPU scores in 3dm06.

I used SetFSB 2.2.134.98, I can't remember which exact setting, since it's 8 months ago I did it. I won't be home to check until maybe next week. Though I curious as well to know what it took to hardmod til PLL chip :) All I can tell you right now, is that I can see from photos that it's a Cypress PLL chip. Will investigate and return with an answer.

Ah, I have a different IDT PLL. I found the Cypress PLL on mouser for $2.80. I'll buy it and switch it out. Messing with old cheap hardware prevents me from messing with and killing my $1k+ stuff. I'll be back at this system tomorrow and can get hardmod info. I think all I did though was solder pins 54 and 55 together. The resulting intermediate voltage gets interpreted as a 1 by the PLL on both frequency select pins. Beware that you memory likely can't handle 444 MHz. I knocked mine down to the 266 MHz strap for 355 MHz. Mobo datasheets here btw: http://www.s-manuals.com/notebook/dell_inspiron_8600

Actually the Mouser part listing is for 2000 part reels...

Yeah I did just solder the S0 and S1 pins together and that got me 533 fsb. Also, you can put 9600xt and 9700 mobile cores on these things: https://imgur.com/a/RuTX2ah