I am attempting to upgrade a PC... Existing.... Intel 233MMX FIC 503+...flashed with the latest Bios Two 32 meg SDRAM Samsung Originals 10ns Maxtor ULTRA EIDE on Primary A couple of CD ROMs on Secondary Maxtrox Mystique 220 PCI Kingston PCI NIC SB32 PNP this setup is a NT4 SP5 ....Win98 S2 dual boot that has been running just fine for six months. I bought a AMD K6 2 400. I was hoping my SDRAM would be fast enough for the 4 X 100Mhz BUS required for the 400 or I would be able to run the SDRAM at 66 in the 503 but this didn't work. The board wouldn't POST at 4 X 100 ...even when I jumpered the RAM to run at 66......so I ordered some PC 100 RAM. In the meantime I set the 400 at 75 X 4 or 300. The setup ran fine for about 5 hours and then I got a video lockup in NT. The screen starts to break up and then locked. I shut down and checked the CPU which is being cooled by a top end PC Power and Cooling CPU cooler.....it was barely warm. Booted back up but this time in 98....tried to run Wintune98 but the screen broke up and locked up during the video test. At this point I reset the CPU to 66X 4 = 266 and rebooted. I still have video lockups in Win98....my screen starts to break up and then locks...sometimes I can still move the mouse ...and soft boot...sometimes it's a hard lock. I am running the AMD at almost half it's rated speed on known stable setup and yet I am having video locks in Win98.....does anybody know of any issues with this chip ? Anybody see anything like this before? m Do you want to signoff PCBUILD or just change to Digest mode - visit our web site: http://nospin.com/pc/pcbuild.html