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Conference hydra::amiga_v1

Title:	AMIGA NOTES
Notice:	Join us in the NEW conference - HYDRA::AMIGA_V2
Moderator:	HYDRA::MOORE

Created:	Sat Apr 26 1986
Last Modified:	Wed Feb 05 1992
Last Successful Update:	Fri Jun 06 1997
Number of topics:	5378
Total number of notes:	38326

5145.0. "Zmodem.... SSSSmoke'n" by CSSE32::SMITH (Reality, just a visible imagination?) Thu Oct 24 1991 21:16

    I had the opportunity to take home a 9600 baud modem.  Boy, I'm I
    impressed with the Zmodem transfer rate...
    
    Sending straight, uncompressed files I can sustain a 1700 byte/sec
    transfer rate.  With LZH files I see about a 1000 byte/sec.
    
    The modem is a CODEX 9600 baud MNP5 with a DTE rate set to 19.2K
    dialing into the same on my VAX.  I sure hope I get to keep this baby
    for a while!
    
    I did find a few problems with the way I had VLTjr Zmodem set up that
    was slowing things down at first that I thought may be of interest to
    others.  First I bumped the "I/O Buffer Size" from a setting of 16KB to
    256KB.  This prevents access to the disk until the end of most files. I
    also changed the "Frame Size" from 1024 to 0.  This made quite a
    difference, not having to ACK after each 1024 bytes.  Not sure why I
    had it set tp 1024 in the first place.
    
    
    Cheers,
    
    ...Ed

T.R	Title	User	Personal Name	Date	Lines
5145.1	Close, but no cigar	ALLVAX::TERELLA	!Mike Terella DTN 287-3083 CTC2-1/C14	`Fri Oct 25 1991 09:30`	10
	I've been using Zmodem at 9600 on a DEC V32 modem. So far using VLTjr the best speed I've seen is about 920 bytes/sec. I (finally) have sufficient memory to boost the buffer size to 1024 (holds a fish disk then some!) but I haven't tried messing around with the frame size. Whatever the defualt is, that's what I'm, using. I'll have to check it and see. It would be nice to break the 1K barrier on .lzh files! -mt
5145.2	I have to use a non-zero value...	XSNAKE::WILSONTL	Lead Trumpet (Read that...LEED!)	`Fri Oct 25 1991 09:53`	9
	Re .0 and the 1024 frame buffer... The Zmodem component on XPRZmodem.library on my 3000 doesn't seem to want to work unless I change the frame buffer to something other than zero (1024 is the value I use now). I also have the prospect of taking home a 9600 and I will probably bump that value up to 4096 or some-odd value. Tony
5145.3	More on 9600 baud	CSSE32::SMITH	Reality, just a visible imagination?	`Sat Oct 26 1991 19:00`	33
	re .1 At 9600 baud 1 kbyte/sec is about tops. The MNP5 compression has little to no effect since the files are already compressed. 9600 baud / 10 bits per char = .96 kbytes per sec. With the DTE rate set to 19.2K and the MNP5 doing compression on regular files, much higher rates can be achived. re .2 If I understand the frame buffer correctly it has to do telling the sender to wait for an ACK every frame buffer size. The problem occurs when using floppy's because of their slow access time. This can cause the sender to timeout with large buffer sizes. In short what I get from reading the docs is if you use a floppy or have a problem when you set your buffer size large, you should set your buffersize and framesize the same. eg: If you set your buffer size to 64k you should set your framesize to 65536 bytes. This will cause the sender to wait for a ACK every 64Kb, thus preventing the timeouts. A setting of zero assumes you will be able to complete the buffer size write to disk before the sender times out. One other nice thing I just discovered about MNP5. My wife just picked up the phone to make a call, heard the computer chatter and came running in here saying sorry. Except for a short delay in echoing my typing, I would not have noticed ;').