SL8HX - Intel Pentium 4 Processor 521 2.80 GHz, 1M Cache, 800mhz FSB, Socket 775 This is a 64-Bit Processor. It will run both 64-Bit and 32-Bit OS’s and Applications. This CPU is in good working order. It was removed from a fully working system and has been cleaned and fully tested. GUARANTEED NOT DOA, WARRANTED FOR 30-DAYS. Please check compatibility with your system before purchasing. Thanks for looking!