Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!shrinkit
From: shrinkit@Apple.COM (Andrew Nicholas)
Newsgroups: comp.sys.apple2
Subject: Re: Zmodem Drivers (repost)
Keywords: Repost of Andy's Zmodem offer
Message-ID: <50982@apple.Apple.COM>
Date: 30 Mar 91 07:58:37 GMT
References: <1991Mar29.145822.11700@isis.cs.du.edu>
Distribution: na
Organization: Apple Computer Inc., Cupertino, CA
Lines: 33

In article <1991Mar29.145822.11700@isis.cs.du.edu> kreme@isis.UUCP (Spam Spam Spam Spam Spam Spam Spam Spam) writes:

>By the way, Andy, how many checks do you have?

So far, 31.  I seem to get -maybe- one every 4-5 days. I'm working on adding
CRC-32 to these drivers and a 16k buffer (instead of the only 8k buffer which
I had planned) and I'll also be providing 3 versions of the drivers -- one
which contains no technical information, another which dumps the packet
information to the screen so those who are technically inclined and
understand the way Zmodem works can watch what the protocol is doing and
learn a little about Zmodem, and another which dumps the packets to both the
screen and printer (so if something is weird, you could fax me a hard copy of
what was going on).

CRC-32 doesn't take (hardly) any more time to calculate than CRC-16... it
takes something like 59 cycles per byte -vs- something like 56 or 54 for
CRC-16, so transferring a file with the better error-detection mode is
just simply a better thing to do (ie, there is no performance loss at all).

Anyhow, that's the shape of things right now.  All my time is currently
consumer by working on the Finder, but I'll find some spare stuff in the
weeks ahead to get the Zmodem project finsihed and out to the folks who paid
me for it.

andy


-- 
Andy Nicholas		  GEnie & America-Online: shrinkit
Apple Computer, Inc.  	 	      CompuServe: 70771,2615    
Apple IIGS System Software		InterNET: shrinkit@apple.com

I'm doing this on my own time, so I don't speak for Apple.