Bryan_Jones_Woodworth@cup.portal.com (06/01/91)
I am planning on buying a modem supporting mnp5 and v.42bis, which allow it to transfer at speeds up to 9600 bps. My question: Will this really go at 9600bps? Will it connect at 9600 with USR HST modems? With any modem that supports v.42bis? Help. I've seen some v.42bis modems that support 9600bps (like the one I want), others that support 19.2K (v.32), 19.2k (v.32/v.42), 38.4k (v.32/v.42bis).. HELP!! How do I know which modem to buy? Is $232 a good deal for a modem that supports MNP5 / V.42BIS compression?? (MNP5 at 4800bps, v.42bis at 9600) I am worried that I won't get fast speed with modems.. I don't know which modems will connect with it at 9600.. help? (i am a novice..) thanks!! Bryan_Jones_Woodworth@cup.portal.com
root@zswamp.uucp (Geoffrey Welsh) (06/02/91)
Bryan_Jones_Woodworth@cup.portal.com wrote: >I am planning on buying a modem supporting mnp5 and v.42bis, >which allow it to transfer at speeds up to 9600 bps. I presume you mean a 2400 bps modem with V.42bis, right? >Will this really go at 9600bps? No. It's a 2400 bps modem, and 2400 bps is exactly how fast its *physical* carrier will go. The advertisement "up to 9600 bps" is based on data compression, which is useless in the vast majority of situations. Still, in an effort to find out exactly how accurate the ads are, I've often sumbitted new V.42bis modems to the test of feeding it a megabyte of nulls and determining how fast it can move them using YMODEM-G... even with ideally compressible data, it never approaches 960 CPS. >Will it connect at 9600 with USR HST modems? Fact #1 (and don't you ever forget it): There is only one modem on Earth that will connect at 9600 (or 14400) bps with a USRobotics Courier HST... and that's the USRobotics Courier HST. This is unlikely to change. USR's Courier HST Dual Standard (sometimes referred to as just "Dual Standard") will also speak to V.32 modems at 9600 (and, with USR's latest models, with V.32bis modems at 14400 bps). No, V.42 doesn't have anything to do with V.32; V.42 is a protocol to packetize data and correct errors, while V.32 describes how bits are to be turned into signals that can be transmitted over the phone line. They perform different jobs, so don't even as if they're compatible (it would be like asking if a Porsche was compatible with orange paint). >I've seen some v.42bis modems that support 9600bps (like the >one I want), They're really 2400 bps modems, but you talk to them at 9600 bps so that the extra throughput (typically 280 CPS for compressed files, much higher on text) can be realized. They don't actually move real data at 9600 bps. >others that support 19.2K (v.32), 19.2k (v.32/v.42), 38.4k >(v.32/v.42bis).. V.32 means 9600 bps full duplex. Again, the modem will speak to the computer at a speed of 19,200 bps (or, for optimistic manufacturers, 38,400 bps), but the modem itself is 9600 bps and typical throughput for compressed files is around 1160 CPS. V.32bis and the 14.4 kbps HST are 14,400 bps modems, and they will move compressed data around 1750 CPS. >I am worried that I won't get fast speed with modems.. Your first worry should be that manufacturers are taking advantage of the general ignorance of the public to make their products sound faster than they really are. Lean back and read this conference for a while, and you'll get a better feel for what all the fancy words mean and what a particular brand of modem can do for you. -- Geoffrey Welsh - Operator, Izot's Swamp BBS (FidoNet 1:221/171) root@zswamp.uucp or ..uunet!watmath!xenitec!zswamp!root 602-66 Mooregate Crescent, Kitchener, ON, N2M 5E6 Canada (519)741-9553 "He who claims to know everything can't possibly know much" -me
rdippold@cancun.qualcomm.com (Ron Dippold) (06/04/91)
In article <42831@cup.portal.com> Bryan_Jones_Woodworth@cup.portal.com writes: >I am planning on buying a modem supporting mnp5 and v.42bis, which allow it >to transfer at speeds up to 9600 bps. My question: > >Will this really go at 9600bps? Will it connect at 9600 with USR HST modems? >With any modem that supports v.42bis? Help. > >HELP!! How do I know which modem to buy? Is $232 a good deal for a modem >that supports MNP5 / V.42BIS compression?? (MNP5 at 4800bps, v.42bis at 9600) If the files you are sending are already compressed, you will get 2400 bps, period. (Actually, about 2800 due to other things MNP5 does for you, but...) If they are not compressed already you can expect maybe 2:1 with text files using V.42bis and maybe 1.5:1 with text files using MNP5. A packing program would do much better. However, it WILL speed up text communications between you and the BBS. Not up to 9600 bps (that's a theoretical maximum), but probably around 4800 bps. $232 seems a bit high for this. -- Standard disclaimer applies, you legalistic hacks. | Ron Dippold