Re: [OT]Modem speed
On 4 Jul 2005, at 23:32, don cole wrote:
>
>
> posted by: don cole <doncole at pacbell.net>
>
> I misstyped I meant to say,
>
> > Which is faster a 28800 modem with a 500 mhz clock.
> >
> > or
> >
> > a 56k modem with a 266 mhz clock?
Well, your question answers itself. 56k is faster than 28.8k, obviously.
The cpu clock doesn't matter at all, as long as the cpu isn't so busy that it
doesn't have time to answer the modem. BUT if the cpu is too busy, the
modem can go unanswered, and the line get dropped (especially true for
winmodems (or other software modems)). Also, it's normal for modems to
"retrain" in the presence of noise/errors, typically dropping to lower and lower
speeds until there's a tolerable level of correctable errors (or no errors). I
know of no modems that will attempt to retrain *up* in speed. This is also
why a 28k modem *can* outrun a 56k modem, if the 28k has error correction
and hardware compression turned on. The type of connection matters too, for
instance, is it full duplex, is it set to echo everything back to the sender (or
just the crc value), is it a true hardware modem or a winblowsmodem, does
your isp support everything the modem can do, etc?
Some of the advanced settings your modem may support for speed might
not be supported by your isp. Some may not be supported by the telco, like
full 56k, which requires cleaner lines and higher drive from the modem. If
there is an a/d convertor in a substation between you and the central office
(the telco will often digitise every line and stuff them down a channelised T1
line, saving them wire and money), you may get only 10k no matter what you
do, because you will be limited to 1/2 the highest voice frequency the a/d
operates at (see: Nyquist).
To make matters worse for measuring, if you set windoze to connect only at
a certain speed, it *may* simply disconnect if there is a burst of noise which
drops the speed down below your forced setting, or it may attempt retrain,
and stay in retrain mode forever. And setting any setting in modem/dialup
setup has no bearing on the actual speed of the connection. Mine reports
115K on both win95B (233 mhz) and on winXP (2.8 ghz), because it's a
external serial port modem (cheaper and easier to replace when lighting
destroys them), and i certainly don't get 115k on a 56k modem connected to
a 10k dialup line.
Best bet: download a huge file and time it. Wget on verbose will do that for
you. Don't even bother with Eu libs for internet downloads, they are too slow
and erratic. Many years ago (man, i feel old), i suggested improvements for
Eu (not gotten any of them) and internet connectivity was one suggestion. I
use only wget for http anymore.
Kat
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