Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uwm.edu!uwvax!shorty.cs.wisc.edu!thaler From: thaler@shorty.cs.wisc.edu (Maurice Thaler) Newsgroups: comp.sys.ibm.pc Subject: Re: XMODEM,YMODEM,ZMODEM,KERMIT Which is best and why? Keywords: ZMODEM, KERMIT Message-ID: <9457@spool.cs.wisc.edu> Date: 2 Jan 90 00:10:12 GMT References: <32428@news.Think.COM> <919@eecea.eece.ksu.edu> Sender: news@spool.cs.wisc.edu Organization: U of Wisconsin CS Dept Lines: 64 In article <919@eecea.eece.ksu.edu> gordon@eecea.UUCP (Dwight W. Gordon) writes: >ZMODEM - >3. Not as robust as KERMIT. > a. noisy environments (bad phone connections) causes troubles > b. multitasking (DesqView) a graphics (high cpu overhead) application > in another window tends to cause retries/packet failures (yes, I > know that there must be a way to tune the DesqView parameters so > that this doesn't happen. I haven't found it!) Sorry Dwight, I don't buy this one. ZMODEM is very robust. 32bit-crc gives your virtually identical files including date and time stamping. Also, as the baud rate goes up the speed difference between ZMODEM and Kermit widens. I use a US Robotics Dual Standard modem and regularly get >1600bps using ZMODEM . Kermit could never do that, not even SuperKermit. If you are having problems with DesqView with DSZ or ZCOMM, I would suggest that it could be either EMS memory management and/or a less than well behaved disk cache that causes intrupt latecency problems (well documented in DSZ.DOC) or a less than wonderful UART. I switched to the NS16550an UART as recommended by Forsberg in the DSZ.DOC (about a $20 mod) and it cleared up all high speed/multitasking problems. This brings up another issue. It seems that several manufacturers (for example DELL) are using VLSI COM ports that are terrible at better than 9600. They can receive data at 19200 perhaps but fail to handle hardware handshaking thus being useless with today's high speed modems which require you to be locked into a bps higher than your connect rate. With my Dual Standard modem, they recommend you lock in at 38,400bps. This would fail every time with these VLSI or ancient UARTS. Also, quite unfortunately, when you buy an i/o card, they always solder in the first UART and leave the second socketed which means that you can only run one high speed UART off of COM2 and not COM1. At any rate, getting back to the original question, KERMIT is ONLY useful for talking to mainframes that have a 7bit data stream over which you want to pass 8-bit binaries. For PC-PC, or UNIX-PC ZMODEM is a clear winnner. BTW, If it wasn't mentioned earlier, if properly implemented, one nice feature of ZMODEM is that the receiving end does nothing to start the download. On my Unix account, I have an "rz" binary that automatically kicks in when I send files from my PC, and with ZCOMM,YAM, and TELIX, the terminal watches the datastream for ZMODEM's init string and automatically starts downloading. This is a really nice feature which sure beats: init download on remote jump back to terminal init download locally I was really disappointed when I checked out the new XTALK for Windows and discovered that their implementation of ZMODEM did not include autodownload. (Neither does WINQVT, but one would hope that the commercial package would have a better implementation than the shareware version |-) ) At any rate, perhaps ZMODEM is not free, but there are an increasing number of programs that implement it. And the price of DSZ, or ZCOMM is still under $50, which is a small percentage of your yearly phone bill using the program... -- Maurice Thaler SYSOP Audio Projects BBS (608) 836-9473 SYSOP Power Board BBS (608) 222-8842