JerryK@cup.portal.com (Jerry E Kindall) (06/19/89)
Zmodem is a very fast protocol, which doesn't require acknowledgement of each block sent. Blocks that aren't correctly sent are NAKed and sent again. Actually, the protocol isn't quite that simple (look at Chuck Forsberg's specs for Zmodem sometime for a real thrill) but that's about the gist of it. The protocol will work fine with Apples because it has a convention for indicating the "buffer size" on the receiving machine. In other words, if ProTERM can only receive 15K of data before it has to save it to disk, the sending computer will only send 15K at a time, then wait for the go-ahead before sending the next chunk. The problem seems to be in ProTERM's implementation of Zmodem. ProTERM's Ymodem is flakey on GEnie as well, but I've personally never had problems with it. In any case, Greg Schaeffer is working with GEnie to get the problems ironed out. By the way, I've used Zmodem here on Portal, and on a local MS-DOS BBS, and ProTERM handles both of those hosts fine. I suspect that the Zmodem Portal and this MS-DOS BBS use differs in some subtle way from Forsberg's specifications. ProTERM probably is off-base in the same direction, which would explain why its Zmodem works with those hosts but not on GEnie. /\ Jerry Kindall JerryK@cup.portal.com \/ Death to COBOL GEnie: A2.JERRY ALink: A2 Jerry
userDBUG@ualtamts.BITNET (Dan Berry) (06/20/89)
In article <8906171926.aa28625@SMOKE.BRL.MIL>, mitchellr@UV4.EGLIN.AF.MIL writes: >TO: _WINS% ( _DDN[INFO-APPLE@BRL.MIL] ) > I was perusing GEnie last night, and saw that they now >support "ZMODEM" protocol. Can anyone on the net fill me in on >the advantages of this protocol? I also read in the A2 >Roundtable that this protocol doesn't work with any current >terminal software for the Apple //. Does anyone have any idea on >who IS going to support it? Well, rumor has it that ProTerm v2.1 (if it's officially out) supports Zmodem file transfer. Zmodem is what is called a "streaming" protocol, as compared to a "packet" protocol. All it really results in is computer A sending the data in a continuous stream, and computer B telling A when it detects an error. Sortof. There's just one catch to it - if you have a noisy phone line, it REALLY sux. However, in this age of error-correcting modems (such as MNP-style modems; the newer 2400 & all 9600's that I know of) it should prove to be beneficial. Hope this helps! +-----------------------------------+ DAN BERRY ! "Violence is the last ! University of Alberta ! refuge of an incompetent." ! Computing Systems +-----------------------------------+ (Network and DataCom)
mitchellr@UV4.EGLIN.AF.MIL (World's Semi-Greatest Fighter Pilot) (07/22/89)
E G L I N A F B
I N T E R O F F I C E M E M O R A N D U M
Date: 17-Jun-1989 06:18pm CDT
From: MAJ RICHARD S MITCHELL
MITCHELLR
Dept: USAFTAWC Air-Air Weapons
Tel No: 904-897-5502
TO: _WINS% ( _DDN[INFO-APPLE@BRL.MIL] )
Subject: ZMODEM/EASYLINK
I was perusing GEnie last night, and saw that they now
support "ZMODEM" protocol. Can anyone on the net fill me in on
the advantages of this protocol? I also read in the A2
Roundtable that this protocol doesn't work with any current
terminal software for the Apple //. Does anyone have any idea on
who IS going to support it?
Different subject: AE's "EASYLINK". I saw it advertised
in this month's Incider, and it looks interesting. Any
experience or comments? It appears from the ads that this may
give Mousetalk a run for the money.
Last subject: How do you make those spiffy little info
footers that I keep seeing tacked on to the ends of messages?
(Just interested....)
Thanks,
Ricknazgul@obsolete.UUCP (Kee Hinckley) (07/22/89)
> support "ZMODEM" protocol. Can anyone on the net fill me in on > the advantages of this protocol? I also read in the A2 > Roundtable that this protocol doesn't work with any current > terminal software for the Apple //. Does anyone have any idea on > who IS going to support it? I've heard ZMODEM as being touted (sp?) as very fast because it doesn't require acking the packets. You only nak ones that don't make it correctly. If true this would make it much faster on high speed modems that have problems with turnaround (Telebit T1000 for instance). However it would also give Apple ][s problems because disk accesses turn off interrupts, and you would lose characters. Maybe you could get around this, but you'd probably have to deal with losing packets and resending them every time you wrote a bunch to the disk. Home: obsolete!nazgul@bloom-beacon.mit.edu Work: nazgul@apollo.com BBS: obsolete!pro-angmar!nazgul@bloom-beacon.mit.edu or nazgul@pro-angmar.cts.com (somewhat slower though) 617/641-3722 (300/1200/2400) -------
gwyn@smoke.BRL.MIL (Doug Gwyn) (07/22/89)
In article <8906180052.AA20316@obsolete.UUCP> nazgul@obsolete.UUCP (Kee Hinckley) writes: >However it would also give Apple ][s problems because disk accesses >turn off interrupts, and you would lose characters. This isn't an inherently insoluble problem, because virtually all UARTs, ACIAs, or whatever in use today are at least double-buffered, giving the operating system one character assembly time to deal with inputting the buffered character. At 2400bps, that's 1/240 seconds, i.e. more than 4 milliseconds. If interrupts are disabled only for shorter duration than that, no received characters need be lost. I don't know how long ProDOS or GS/OS disables interrupts during I/O for the various kinds of supported disk drives, but all of them should be able to transfer a sector in less than 4 msec.
mitchellr@UV4.EGLIN.AF.MIL (World's Semi-Greatest Fighter Pilot) (07/22/89)
E G L I N A F B
I N T E R O F F I C E M E M O R A N D U M
Date: 17-Jun-1989 10:04am CDT
From: MAJ RICHARD S MITCHELL
MITCHELLR
Dept: USAFTAWC Air-Air Weapons
Tel No: 904-897-5502
TO: _WINS% ( _DDN[INFO-APPLE-REQUEST@SMOKE.BRL.MIL] )
Subject: ZMODEM/EASYLINK
I was perusing GEnie last night, and saw that they now
support "ZMODEM" protocol. Can anyone on the net fill me in on
the advantages of this protocol? I also read in the A2
Roundtable that this protocol doesn't work with any current
terminal software for the Apple //. Does anyone have any idea on
who IS going to support it?
Different subject: AE's "EASYLINK". I saw it advertised
in this month's Incider, and it looks interesting. Any
experience or comments? It appears from the ads that this may
give Mousetalk a run for the money.
Last subject: How do you make those spiffy little info
footers that I keep seeing tacked on to the ends of messages?
(Just interested....)
Thanks,
Rickpaul@athertn.Atherton.COM (Paul Sander) (08/03/89)
In article <10417@smoke.BRL.MIL>, gwyn@smoke.BRL.MIL (Doug Gwyn) writes: > This isn't an inherently insoluble problem, because virtually all UARTs, > ACIAs, or whatever in use today are at least double-buffered, giving the > operating system one character assembly time to deal with inputting the > buffered character. At 2400bps, that's 1/240 seconds, i.e. more than 4 > milliseconds. If interrupts are disabled only for shorter duration than > that, no received characters need be lost. > > I don't know how long ProDOS or GS/OS disables interrupts during I/O for > the various kinds of supported disk drives, but all of them should be > able to transfer a sector in less than 4 msec. True, they _should_ be able to transfer a single sector in 4ms. The problem is that most communication programs (all of the ones I've ever used, and all of the ones that people I know have used) tend to buffer up the data and write many sectors at once. Worse, for those who transfer to floppy, the drive has a 1-second spin-up time. I don't know about anyone else, but I wouldn't count on interrupts being enabled during that time, at least not when using a Disk ][. -- Paul Sander (408) 734-9822 | If a machine is powerful enough paul@Atherton.COM | to have a DWIM button, why bother {decwrl,sun,pyramid}!athertn!paul | with the button? -- Eric Black
JerryK@cup.portal.com (Jerry E Kindall) (08/03/89)
It's true, no terminal program currently works with GEnie's ZMODEM. However, ProTERM's ZMODEM works fine here on Portal for me, and also works fine on a local MS-DOS BBS. Greg Schaefer, the author of ProTERM, is reputedly working on making ProTERM compatible with GEnie -- no word on when that'll be do though. As for EasyLink: I've heard it's a pretty darn good terminal program. Its main competition won't be MouseTalk, though, it'll be ProTERM. EasyLink is the only terminal program I'd consider giving up ProTERM for, basically because of its excellent macros. /\ Jerry Kindall JerryK@cup.portal.com \/ Death to COBOL GEnie: A2.JERRY ALink: A2 Jerry