bert@helix.nih.gov (Bert Tyler) (12/01/90)
> Initially, I was very pleased. It was plug and play. It supports V.32, > V.42, V.42bis, MNP2-4, and MNP5. I had no difficulty at all dialing up > the University's V.32 modems (MNP5). 9600 bps was sure a lot nicer than > 2400 bps. I played with the registers allowing Data Compression and > Error Correction. I found that _disallowing_ Data Compression yielded > higher data transfer rates! This was true both for compressed files > (.ZIP) and for text files. This was suprising, especially in the case > of text files. > ... > Conclusions: > > Disallow Data Compression for higher data transfer rates, > on ALL types of files! Data compression on text files works fine for me and everybody else I have heard from. It sounds like something was wrong with your setup or modem. Did you have your modem <-> PC connection set at a higher connect rate than 9600 bps (say, 19200 or 38400)? Was the modem on the other end set up the same way? If *either* of the modems is connected to its computer at 9600 bps, then there is no way that they will be able to transfer information at a data rate faster than 9600bps, and in fact the extra overhead of both handling modem<->modem data compression and constantly telling the modem on the other end to slow down *could* lower your effective transfer rate. Think of it as pumping water through a series of pipes - the final flow rate is going to be determined by (among other things, I know) the smallest section of pipe in the sequence.
kjh@pollux.usc.edu (Kenneth J. Hendrickson) (12/02/90)
In article <696@nih-csl.nih.gov> bert@helix.nih.gov (Bert Tyler) writes: >> I found that _disallowing_ Data Compression yielded >> higher data transfer rates! This was true both for compressed files >> (.ZIP) and for text files. This was suprising, especially in the case >> of text files. >> ... >> Conclusions: >> >> Disallow Data Compression for higher data transfer rates, >> on ALL types of files! > >Did you have your modem <-> PC connection set at a higher >connect rate than 9600 bps (say, 19200 or 38400)? Was the modem on the >other end set up the same way? I don't know about the modem at the other end, but my modem was set up at both 9600 bps and 19200 bps for these tests. The results were the same for both computer<->modem rates. This probably indicates that the connection at the other end was at 9600 bps. The compression used was MNP5, since the modem at the other end doesn't have V.42bis. What bothers me the most about this modem is that it doesn't work at all at bit rates <= 2400 bps. This is on clean local lines that another modem (Avatex 2400) has absolutely no problem with. Since there are many modems out there at <= 2400 bps, and many systems without >= 9600 bps modems yet, this is unacceptable. I am currently using the modem at 9600 bps to read the news, and construct this reply. It works reasonably well at 9600 bps. Still, it's not acceptable, cuz it won't work at <= 2400 bps. ("This modem" is a Practical Peripherals PM9600SA rev. 1.05) -- favourite oxymorons: student athlete, military justice, mercy killing Ken Hendrickson N8DGN/6 kjh@usc.edu ...!uunet!usc!pollux!kjh
burris@highspl (David Burris) (12/02/90)
From article <28557@usc>, by kjh@pollux.usc.edu (Kenneth J. Hendrickson): > What bothers me the most about this modem is that it doesn't work at all > at bit rates <= 2400 bps. This is on clean local lines that another > modem (Avatex 2400) has absolutely no problem with. Since there are > many modems out there at <= 2400 bps, and many systems without >= 9600 > bps modems yet, this is unacceptable. > > I am currently using the modem at 9600 bps to read the news, and > construct this reply. It works reasonably well at 9600 bps. Still, > it's not acceptable, cuz it won't work at <= 2400 bps. > > ("This modem" is a Practical Peripherals PM9600SA rev. 1.05) I just picked up one of these. I don't have it working on the UNIXPC yet but in my trials on another computer (no UUCP) I was able to connect at both 1200 and 2400 without compression or correction. I have it working to dial out at 1200 baud on the UNIXPC and am working on the modem settings to get highs to work correctly. If I have problem wiht this modem, you can bet I'll be vocal about it. -- ================================================================ David Burris Aurora,Il. burris@highspl {att | uunet}!linac!highspl!burris ================================================================