Recommended Tests

On my 6800gt there is 2D clocks and 3D clocks.  This allows for gaming and nongaming setups such as underclocking on desktop and boosing both the fequencies and fan in 3D.  My 8600gt doesn't have that ability and I would of been forced to have the card run at one and only one fequency if not for finding this guide.  By creating profiles with Rivatuner I can save my stock and OC settings and access them with a simple right click.

Um if there is no temp sensor its    your best guess.  I would suggest "ATI tool", its a small overclocking program with built in artifact testing.  If your gpu's overclock can pass the test for 15minutes and not blow-up, its stable as a rock.
RivaTuner 2.0 fan speed & Overclock Guide
3DMark01 result search with P4 and FX5500

just so we're clear... if the card fails the gpu releases the magic blue smoke?

also, its a little known fact if you capture the "magic gas" released by the card and infuse it with your gas in the car, you will get 275 MPG.

i never thought about it, it's worth a try

4X will work on a 8X board but not the other way around!

I read that the 6800gt (near top of the line) 8x agp scored within 3% of the 6800gt 4x agp.  Here, PCI Express 2.0 Graphics Cards Tested, shows that the $600 9800GX2 scores the same on 3Dmark06 with x16 lanes as it does with x4 lanes.  With only a single lane the 3DMark result drops by 67%!  If my estimates are correc...close, then 3DMark06 used 740MByte/sec.  All this to say, "I don't think agp 8x is that much better then 4x, especially with your rather old card.  I could be wrong, hard to believe isn't it.  Remember theres a lot of marketing ploy out there."

AGP 1x is 264 Mbytes/sec.      PCIe 1.1 1x is 250MByte/sec         PCIe 2.0 1x is 500MByte/sec 
AGP 2x is 528 Mbytes/sec.      PCIe 1.1 4x is 1GByte/sec             PCIe 2.0 4x is 2GByte/sec
AGP 4x is 1 GByte/sec.           PCIe 1.1 8x is 2GByte/sec             PCIe 2.0 8x is 4GByte/sec
AGP 8x is 2 GBytes/sec          PCIe 1.1 16x is 4GByte/sec           PCIe 2.0 16x is 8GByte/sec

Many cards have built in throttling such that if temps go to high the card with underclock itself to prevent damage.  If your overclock leads to lower results that might be happening, but you don't have a temp sensor to know if thats the case! lol 

Actually, that's Alienware. In other words, the OC is nothing special. Unless you get a real poor sample, any CPU with that kinda multi (extreme ones have an unlocked multi even) can reach 4 GHz without increasing the FSB too much. The only thing holding 45nm C2D and C2Q back is FSB really.