330 FSB works, but not 333?

[blufire]

I know there's got to be a good reason for this, but I guess just don't have the experience to determine it... Here's the backstory: I've been running a water-cooled rig for a solid 6-9 months now, and it's been great. The only problem is I have not been fully able to take full advantage of the increased overclocking margins yet.

I've had the system sitting at just below 3.0 Ghz (330x9) with no problems at all. Orthos runs for days on end without any problems. But when I increase the FSB speed by just 3 mhz to 333, everything falls apart. It boots, but within 4-8 minutes of running orthos, I get errors. I've tried increasing Vcore and the Vtt, relaxing memory timings, with no success. The memory/ram ratio is at 2:3 I believe, leaving the actual DRAM speed at 1000 mhz.

Is it a coincidence that things break down at exactly a FSB speed of exactly 333 Mhz? What might cause this, and where should I start looking? Here are some pieces of info that might help:

- E6600 running at 3.0 Ghz
- FSB: 333 Mhz
- Memory/DRAM divider: 2:3
- Memory Timings: 4-4-4-12 @ 1000 Mhz
- Motherboard: ASUS P5B Deluxe
- Vcore: 1.4V
- Vtt: 1.2V (tried 1.3V, doesn't help)
- Northbridge voltage: 1.45V

Let me know if I should provide any other info. Thanks in advance!

[hstuehmeyer2000]

loosen up your ram timings to 5-5-5-15

[Loser777]

Maybe your FSB Wall is 330...

[blufire]

Hmmm... loosening the timings seems to have worked, although I swear I tried that before... Orthos is running stably at 1 hour, which is definately an improvement over 4 minutes :)

What's the reasoning behind loosening timings, and is there some sort of rule of thumb for matching timings with the rest of the system?

Also, regarding the FSB hole/wall, how are you supposed to test for stability by incrementally upping the speed, when the hole/wall is supposedly 50-70 Mhz wide? Isn't that kind of dangerous? It's certainly how I fried my last P5B: I set the divider to 1:1, set the FSB to 400, and the CPU multiplier to 8x... within 20 minutes of running Battlefield 2, silicon started burning. :O

Thanks for the help thus far, I'll see how stable this is running at 333 FSB.