njm@cel (10/23/90)
I'm in the market for a modem capable of the following speeds / modulation /
compression modes: v21, v22, v22bis, v32, v42, MNP 5. For space reasons I would
prefer to be able to fit the modem inside my PC-AT. Having looked through
various brochures, I like the look of the Dowty Mayze 96 PC.
(Now the million $ questions. ;-))
Has anyone had any experience, good or bad, of this modem?
Are there similar but better modems available?
Are there any very strong reasons for not getting an internal modem?
Thanks in advance,
Nick.
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-
Name: Nick Mann. E-Mail: nmann@cel.co.uk nmann@cel.uucp
V-Mail: +44 442 230000 ext 3537 ..!{mcvax,ukc,uunet}!cel!nmann
"Sorry to interrupt the festivities", said Hal, "but we have a problem."
*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-ronald@robobar.co.uk (Ronald S H Khoo) (10/23/90)
In article <6758@suns401.cel.co.uk> njm@cel.uucp () writes: > I'm in the market for a modem capable of the following speeds / modulation / > compression modes: v21, v22, v22bis, v32, v42, MNP 5. Why MNP 5 ? Or more to the point, why don't you specify V.42bis ? Specifying MNP 5 rather than V.42bis is probably a mistake. Specifying both might be reasonable if you absolutely need compatibility, though. > Are there similar but better modems available? The one which comes to mind is the Hayes Ultra which *does* have V.42bis as well. > Are there any very strong reasons for not getting an internal modem? Yes. Many. They are a mistake. 1) it can be damn near impossible to debug difficult connexions without the blinkenlights 2) Their serial interface is builtin, so 2a) You are at the mercy of whatever serial chips, etc they use, and its compatibility with the software you're driving it with. 2b) It's a "dumb" serial interface, so you lose significant amounts of CPU power if you're driving it at the kind of speeds that V.42bis over V.32 can give you. 2c) It uses up a whole interrupt by itself which you will curse when you come to want to add more peripherals to the PC. 2b is probably only important if you are multitasking, and together with 2c, only a disadvantage if you ever exercise the option of getting an intelligent serial card, and I suppose that's normally only an option for multiuser PC applications. But 1) is VERY important. Don't underestimate it. -- ronald@robobar.co.uk +44 81 991 1142 (O) +44 71 229 7741 (H)
bob@MorningStar.Com (Bob Sutterfield) (10/23/90)
In article <1990Oct23.063532.21901@robobar.co.uk> ronald@robobar.co.uk (Ronald S H Khoo) writes: In article <6758@suns401.cel.co.uk> njm@cel.uucp () writes: Are there any very strong reasons for not getting an internal modem? Yes. Many. They are a mistake. Your list is a good one. But if a laptop/portable user doesn't want to lug around the extra box, cabling, and power supply brick, then the convenience of an internal modem may become a more important factor. For a machine that sits on a desk, get a good serial interface card and a separate modem. For a machine that hangs from a shoulder, an internal may make sense.
pete@Octopus.COM (Pete Holzmann) (10/24/90)
ronald@robobar.co.uk (Ronald S H Khoo) writes: >In article <6758@suns401.cel.co.uk> njm@cel.uucp () writes: >> Are there any very strong reasons for not getting an internal modem? > >Yes. Many. They are a mistake. >1) it can be damn near impossible to debug difficult connexions without > the blinkenlights But on a PC, there are freebie TSR programs available that simulate the lights! >2) Their serial interface is builtin, so > 2a) You are at the mercy of whatever serial chips, etc they use, > and its compatibility with the software you're driving it with. > 2b) [Restating the same thing] True! Although (2) below sometimes eliminates this problem. Seems to depend on how the modem hardware is set up. On the other hand, there are a few significant advantages to internal modems, in certain situations: (1) Cabling is rather easy [nice for novice users] (2) [On certain modems] No hassles about hardware handshaking. The modem *knows* whether or not your program has grabbed the data. If you have a high-speed modem with end-to-end flow control, this completely eliminates the need for a fancy serial chip. (3) [Most important of all, if it applies] There are no power supply hassles. Your PC's power takes care of the modem as well. The nicest thing about a laptop is that it has a built-in UPS! Add an internal modem and you have a PC that won't go off-line when the power goes out. You also won't be stuck when you travel overseas. Rather nice. Pete -- Peter Holzmann, Octopus Enterprises |(if you're a techie Christian & are 19611 La Mar Ct., Cupertino, CA 95014 |interested in helping w/ the Great UUCP: {hpda,pyramid}!octopus!pete |Commission, email dsa-contact@octopus) DSA office ans mach=408/996-7746;Work (SMI) voice=408/985-7400,FAX=408/985-0859
cec@cup.portal.com (Cerafin E Castillo) (10/25/90)
Nick,
I would have to agree with all of the negative
reponses on internal PC-modems. I'd like to add one more
gripe--the lack of on-board non-volatile memory. This only
gets worse in the following situations:
1) The modem is ONLY dip-switch settable.
2) the modem is software programmable.
If you have dip-switches and need to re-configure your modem
for some modulation, flow control, or feature change, you're
stuck taking your PC apart to get at the dip-switches.
If your modem is software programmable such as the TELEBIT modems,
They so populate the PC modems that there is no room left for
non-volatile memory to save the modem configuration. This means
re-initializing the modem on boot each time. Easy for software,
but not so easy if this means your UUCP system dies every night
of a power glitch which erases the modem.
If you are considering an external modems with all the goodies
you've mentioned, give the TELEBIT T2500 or T1500 a try. V.32
with 2400/1200/300, V.21/V.23, V.42/V.42bis, MNP 4/5, UUCP-
Kermit-Xmodem-Ymodem Protocol Support in PEP AND V.32(!!! :-),
also TELEBIT PEP modulation for 18,031 bps data rates.
Give me a call if you would like more info...
===============================================================================
Cerafin E. Castillo || //\\ ||\\ ||
Network Consultant || //__\\ || \\ || Los Altos
Los Altos Networks || // ---\\|| \\|| Networks
340 Second St. #6 ||___// \|| \\|
Los Altos, CA 94022
(415) 941-8031 UUCP: {apple,sun,uunet}!portal!cup.portal.com!cec
NTERNET: cec@cup.portal.com
"...No hay mal que por bien no venga..."
===============================================================================
=bill@bilver.UUCP (Bill Vermillion) (10/27/90)
In article <1990Oct24.142824.23134@Octopus.COM> pete@octopus.COM (Pete Holzmann) writes: >ronald@robobar.co.uk (Ronald S H Khoo) writes: >>In article <6758@suns401.cel.co.uk> njm@cel.uucp () writes: >>> Are there any very strong reasons for not getting an internal modem? >>Yes. Many. They are a mistake. (reasons 1 & 2 about lights and interface omitted - wjv) Reason # 3) - (for not using an internal modem) You are giving that mean old lady, Ma Nature, direct access to your data bus. A nice lighting hit anywhere in a mile or so can just zip down the phone line, into the modem, onto the bus, and from then on anywhere it wants. In Lightning World, that entertainment center that completely surrounds Disney World, FL, I have lost 3 modems to lightning. All external. The died fighting to save the cpu. On the other hand I know a person who had an internal modem. The lightning entered his computer through the phone connection, got onto the bus through the modem, destroyed the modem, the video display card, and the motherboard. The power supply and the case survived. He was lucky the printer didn't get taken out with the lp port on the video card. And you can always keep lightning out of the computer if you spend enough money. The only way I can see to keep it out when connected to phone lines would be some units with opto-isolation. Are those made.? An interesting sidenote. Most mfrs. will not warrant their equipment for lightning damage. However at one time (I don't know if this still is true) anyone in this area who had a Hayes get hit, sent it back, and typically Hayes repaired it free of charge. Sold a LOT of modems that way. Fix one or two, and sell 100 more. Last Hayes I bought however was $650 for a 1200 BPS back in 1982. That was only a couple of hundred more than the first Hayes modem I had. 300 bps S-100 card, that I think Dennis made in a garage type operation. I had a lightning strike about 50' feet away last year, that tore the bark from a 100' pine tree down to the ground. My Trailblazer stopped answering the phone. Actually it answere, and went thtough all the motions, except picking up the line. Line relay appeared to be hung. TB fixed it but said next time there would be a charge as it was a non-warranted type problem. Anyway - the $50 or so premium you pay for an external buys you enough chips willing to sacrafice their lives for your computer to make it a must for me. Think of an external modem as a fairly expensive lightning supressor. ;-)/2 -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP
shwake@raysnec.UUCP (Ray Shwake) (10/29/90)
bill@bilver.UUCP (Bill Vermillion) writes: >A nice lighting hit anywhere in a mile or so can just zip down the phone >line, into the modem, onto the bus, and from then on anywhere it wants. >In Lightning World, that entertainment center that completely surrounds >Disney World, FL, I have lost 3 modems to lightning. All external. The >died fighting to save the cpu. Were any of these modems "protected"? A number of power conditioners (like my C/A Power Director) provide isolation for RJ11 devices as well as those running off the AC. I would venture that this provides at least as much protection (though feeding an internal modem) for my CPU as an external modem. Experience has taught that all computer equipment of any value should have *some* protection against line irregularities, though there's *no* protection against *all* such irregularities.
darcy@druid.uucp (D'Arcy J.M. Cain) (10/29/90)
In article <1249@bilver.UUCP> bill@bilver.UUCP (Bill Vermillion) writes:
[ suggesting external modem as lightning protection ]
There is certainly something to be said about external modems affording
more protection for the computer in a lightning storm but don't rely on
that to absolutely protect you. A bad enough strike can still go through
the external modem, down the RS-232 and fry your box. If a lightining
storm hits your only real protection is to shut down, unplug all equipment
and disconnect the phone from the phone line.
--
D'Arcy J.M. Cain (darcy@druid) |
D'Arcy Cain Consulting | I support gun control.
West Hill, Ontario, Canada | Let's start with the government!
+ 416 281 6094 |linwood@cbnewsk.att.com (linwood.d.johnson) (10/30/90)
In article <1990Oct28.175259.5849@druid.uucp>, darcy@druid.uucp (D'Arcy J.M. Cain) writes: > In article <1249@bilver.UUCP> bill@bilver.UUCP (Bill Vermillion) writes: > [ suggesting external modem as lightning protection ] > > There is certainly something to be said about external modems affording > more protection for the computer in a lightning storm but don't rely on > that to absolutely protect you. A bad enough strike can still go through > the external modem, down the RS-232 and fry your box. If a lightining > storm hits your only real protection is to shut down, unplug all equipment > and disconnect the phone from the phone line. > It is true that a lightning strike can fry a modem and the pc that is connected to the modem. But, they do make equipment for protection from that type of thing. I have never used any of this equipment though. I just thought it was appropriate interject this bit here. +===================================================================+ | Linwood D. Johnson | linwood@ihlpf.att.com | +-------------------------------------------------------------------+ | Disclaimer: Opinions expressed here are mine and mine only. | | Besides, who else would want them? | +===================================================================+ -- +===================================================================+ | Linwood D. Johnson | linwood@ihlpf.att.com | +-------------------------------------------------------------------+ | Disclaimer: Opinions expressed here are mine and mine only. |
pete@Octopus.COM (Pete Holzmann) (11/02/90)
> In article <1249@bilver.UUCP> bill@bilver.UUCP (Bill Vermillion) writes: > [ suggesting external modem as lightning protection ] If you want something to help stave off electrical surges coming in via a modem line, it is much cheaper to put a surge protector on the modem line than to use a modem for this purpose! There's a little-advertised protector made by Curtis (I believe the SPM-15) that does the trick. The nice thing about it is that it is cheap (around $10-15) and it only needs a ground line (so it works in both 120 and 240 volt environments). On the other hand: If your phone line takes a real lightning hit, you can probably say goodby to anything that was directly connected to the line! The best thing I know of to avoid this problem (other than disconnecting the line or moving to the Sahara :-)) is an opto- isolator. Haven't seen (nor investigated) availability of these things for modem lines; we've occasionally built them up by hand for various serial lines in campus settings. Does anybody know of a source for optically-isolated phone connectors and/or RS-232 connectors? -- Peter Holzmann, Octopus Enterprises |(if you're a techie Christian & are 19611 La Mar Ct., Cupertino, CA 95014 |interested in helping w/ the Great UUCP: {hpda,pyramid}!octopus!pete |Commission, email dsa-contact@octopus) DSA office ans mach=408/996-7746;Work (SMI) voice=408/985-7400,FAX=408/985-0859