On Thu, Sep 13, 2001 at 12:12:40PM +0800, Daniel O. Escasa wrote:
> ** Sabi ni Dido noong Mon, 10 Sep 2001 17:21:31 +0800
>
> > An external modem has a far better chance of working with Linux than
> > any internal modem of any kind ever will. Your particular internal
>
> But still not 100%. I also thought at first that external modems were not
> dependent on Windows until I read about one on another mailing list, and
> actually saw another at a shop in Cybercity@Shang. Price was too good to be true
> -- less than PhP2,000 -- and when I checked the box, I found that it *required*
> Windows. Had to resort to a Diamond Supra at a 66% premium but at least I was
> sure it worked. While the software was Windows-based, the modem itself didn't
> require Windows.
If I understand the way these software modems work, its that the only
real hardware they contain is A/D and D/A converters that operate in
full duplex over the phone line. The computer's CPU has the
responsibility for interpreting those signals and generating the
appropriate responses. That work's usually done by a custom DSP chip
on a real modem. In order to make a software modem, you need a high
bandwidth bus that will allow the computer's CPU to receive these
signals and send back its responses in time. For 56K operation,
you'll need a considerable amount of bandwidth; the 115.2k bandwidth
of standard RS-232 is way too low, even the 12mbps provided by USB is
still not sufficient.
This is why writing a generic driver for software winmodems is very
difficult to do for Linux. Some of the algorithms to make a software
modem are patented by the hardware manufacturers, all in all it's a
complicated issue.
If a serial modem is actually stated to REQUIRE windows, then that
probably means either 1. the modem does not follow the Hayes/AT
command set that is standard for all modems, or 2. you *will* be able
to use the modem under Linux, just that some spiffy features will be
unavailable, or 3. the manufacturer is just completely ignorant of any
other operating systems (this is by no means uncommon) and the Windows
required label is just a lot of smoke. I don't see how (1) is
possible; even USB modems actually use the AT command set, and AFAIK
there are no patents or other IP restrictions on it.
By the way, I bought a 56k external modem by CNet for less than PhP2k,
however it was not much less than PhP2k, and yes, the box stated that
Windows was required. But it's happily chugging along with Linux
anyway, and I've been using it for more than a year. I've also never
inserted the CD that came along with it; maybe my sister's using it as
a coaster :)
The situation is different for USB modems however. There's a standard
for controlling USB modems, called the abstract control model (ACM),
and all of these ACM-compliant modems will work with Linux. But there
are a lot of other USB modems that use proprietary methods for
control, and these are definitely going to be dependent on proprietary
drivers that won't exist for Linux.
--
Rafael R. Sevilla <[EMAIL PROTECTED]> +63(2) 8177746 ext. 8311
Programmer, InterdotNet Philippines +63(917) 4458925
http://dido.engr.internet.org.ph/ OpenPGP Key ID: 0x5CDA17D8
_
Philippine Linux Users Group. Web site and archives at http://plug.linux.org.ph
To leave: send "unsubscribe" in the body to [EMAIL PROTECTED]
To subscribe to the Linux Newbies' List: send "subscribe" in the body to
[EMAIL PROTECTED]
