OC'ing my E8500 3.16

Let me start off by saying this is kind of a multi part question.

I was messing around with overclocking my e8500 last night. I was able to get it up to 3.8 OK and stable. However I wanted to get it up to 4ghz or so. I got it to 4 with a 9.5m and 444 fsb but couldn't get it to pass a prime95 stress test for more then a few minutes. I know it's possible that maybe my chip just can't go that high but from what I read out on the internets is 3.8 is pretty modest for that chip. this is on a standard asus pk5 board with an after market heat synch/fan. One thing however ( and here is the multi part of the question) is my memory setup. Right now I'm running 6 gigs of ram. I have 4 gigs of Gskill ddr2 1066 and 2 gigs ddr2 800 memory. I know I should probably just bust it down to the 4 gig gskill stuff and see how it runs right? But would I benefit more from pushing my cpu to 4ghz and loosing 2 gig of memory but gaining the fact that my memory is running faster. Or leaving it at 3.8 and using the 6 gigs of ram running at a slower 800 speed?

I primarily game on this computer. Im not I guess what you would call hard core but I do like to play newer more graphic intensive games. I'm planning on a video card upgrade from my evga 8800gt to either maybe a gtx460 or a HD 5000 series card depending on the price drop at xmas time.

Any thoughts?

Well I was doing more prime testing and I was wrong. At 3.8ghz 9.5 multiplyer and 400 fsb. It's still not stable. I think there are more settings that I may be needing to mess with. I've played with the cpu voltage and havn't been able to find a good match. I'm at work right now but will list settings later. I'm also going to take out the 2 gigs of 800 memory and just test with the 4gigs of 1066.

I had an e8400 that did 4ghz easily. If you want to see if your memory is the issue try memtest. Running your mixed memory may be an issue, are you running your memory asynchronous? Also what vcore are you using. IIRC you should be good up to 1.35v. I believe I was pumping 1.3v into my e8400. What are your temps with your overclock?

I took out the 2 gig's of ddr2 800 memory. Set the memory to 5,5,5,15 timeing at 1066. The Vcore ( I'd have to check again what it's at) but I think it's just under 1.3v. Right now I'm running at 3.8mhz stable with core temps around the 48c and 57c full load.