ZMax

ZMax is a file transfer protocol developed in 1990-1991 by Mike Bryeans (Micro TECH Systems) who also developed TMODEM. Zmax is designed to replace ZMODEM. It uses 32 bit CRC's on file data blocks, the same as Zmodem, and 32 bit CRC's on its information blocks where Zmodem uses 16 bit. In stream mode Zmax sends blocks, the size being set by the receiver, of data but doesn't require ACKs from the receiver. Zmax should (depending on equipment, phone lines, implementation, etc.) allow about 97.5 percent efficiency at 2400 baud on a 30K file compared to Zmodem's 95 percent. Unlike Zmodem, Zmax reaches full speed on considerably smaller files. In fact, due to less overhead associated with small files, it achieves a better efficiency rating.