ZMax
Encyclopedia
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.
In Non-Stream mode (which can be set by the receiver or the sender), Zmax is a super Batch Xmodem
or Ymodem
depending on the block size, because it uses 32 bit CRCs instead of 16.
Unlike Zmodem which sets an upper limit of 1024 bytes on block sizes, Zmax has an upper limit of over 32K. Because of this, Zmax may be used as a mailer protocol without any modifications.
Zmax also has a lot less CPU overhead than Zmodem, so slower computers can drive highspeed modem
s faster. Zmax does not encode each byte of data like Zmodem does. This reduces the amount of CPU overhead and simplifies the code quite a bit. Zmax also treats all files as binary 8 bit files and will require word length to be set to 8, which is the most common setting.
File transfer
File transfer is a generic term for the act of transmitting files over a computer network or the Internet. There are numerous ways and protocols to transfer files over a network. Computers which provide a file transfer service are often called file servers. Depending on the client's perspective the...
protocol developed in 1990-1991 by Mike Bryeans (Micro TECH Systems) who also developed Tmodem
Tmodem
Tmodem is a file transfer protocol developed in 1990 by Mike Bryeans of Micro TECH Systems. Tmodem is derived from the HTMS protocol Translink with special modifications so that it works well with BBS systems and terminal programs.-External links:* *...
.
Zmax is designed to replace Zmodem
ZMODEM
ZMODEM is a file transfer protocol developed by Chuck Forsberg in 1986, in a project funded by Telenet in order to improve file transfers on their X.25 network...
. It uses 32 bit CRC
Cyclic redundancy check
A cyclic redundancy check is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data...
'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
Baud
In telecommunications and electronics, baud is synonymous to symbols per second or pulses per second. It is the unit of symbol rate, also known as baud rate or modulation rate; the number of distinct symbol changes made to the transmission medium per second in a digitally modulated signal or a...
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.
In Non-Stream mode (which can be set by the receiver or the sender), Zmax is a super Batch Xmodem
XMODEM
XMODEM is a simple file transfer protocol developed as a quick hack by Ward Christensen for use in his 1977 MODEM.ASM terminal program. XMODEM became extremely popular in the early bulletin board system market, largely because it was so simple to implement...
or Ymodem
YMODEM
YMODEM is a protocol for file transfer used between modems. YMODEM was developed by Chuck Forsberg as the successor to XMODEM and MODEM7, and was first implemented in his CP/M YAM program...
depending on the block size, because it uses 32 bit CRCs instead of 16.
Unlike Zmodem which sets an upper limit of 1024 bytes on block sizes, Zmax has an upper limit of over 32K. Because of this, Zmax may be used as a mailer protocol without any modifications.
Zmax also has a lot less CPU overhead than Zmodem, so slower computers can drive highspeed modem
Modem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...
s faster. Zmax does not encode each byte of data like Zmodem does. This reduces the amount of CPU overhead and simplifies the code quite a bit. Zmax also treats all files as binary 8 bit files and will require word length to be set to 8, which is the most common setting.