Hi! I just made some routines for sending data between my PC and my turbo R. The routines are as optimized as I could get them. Results: PC -> turbo R (R800 mode) : 14 kilobyte per second PC -> turbo R (Z80 mode) : 3.6 kilobyte per second turbo R (R800 mode) -> PC : 12 kilobyte per second turbo R (Z80 mode) -> PC : 3.2 kilobyte per second To estimate the number of errors, I transferred the same 16K data back and forth a lot of times. After 2500 transfers, an error occurred. So I was able to send 16K * 2 * 2500 = 80,000K before the first error. I think it's safe to say that a 32 bit CRC is overkill... However, to backup a harddisk, some simple error detection is necessary. Bye, Maarten **** MSX Mailinglist. To unsubscribe, send an email to [EMAIL PROTECTED] and put in the body (not subject) "unsubscribe msx [EMAIL PROTECTED]" (without the quotes :-) Problems? contact [EMAIL PROTECTED] (www.stack.nl/~wiebe/mailinglist/) ****