Since you dont say which CPU you are working with, only what it WAS set at (the 4.5x83.3 = 375MHz), and that makes it very hard for anyone to guesstimate what it might be capable of.
There were 300MHz, 333MHz, 350MHz, and 380MHz versions. LMK which one you have, Okay?
I expect that you have a 300MHz version, which the previous owner of your confuser overclocked to 4.5x83.3 = 375 and you've simply tried to 'push' it farther than it's willing to go.
I have a K6-2 300 here that is quite happy at 4.5x83.3 = 376, and it will do 4.0x100 = 400 MHz, but it isn't 100% stable at 400.
It was good enough to hold still long enough for a 'pretty picture' though...
Here is my new PCChips M848A' ">http://img.photobucket.com/alb...2_T-2-3-3-6-2_M848.jpg v2.1, with a 1700+ @ 2411 MHz, and my trusty old PCChips M810L' ">http://members.lycos.co.uk/mmm...00MHz_Sandra_tests.jpg v7.1A, with a Barton 2500+ @ over 3500+. Some of my fancy cars are on this pag