Paul Guertin wrote: > > CRC-16, actually, with a CRC for each 256-byte sector. > Thanks, Paul. That accounts for the speed. -- Thank you for your time and interest. I hope it was helpful or at least interesting. Phoenyx, Apple2 user since March 1984 Links to Phoenyx's pages: preferred..... http://zip.to/Phoenyx_A2 alternate..... http://www.tinyangeldesigns.com/Apple2