| From: | Matt |
| Date: | 26 Jul 2001 at 23:50:47 |
| Subject: | Re: Different modem performances & AA23 |
Hello Nicholaus
On 26-Jul-00, you wrote:
> Hello,
>
> Just reading through the latest issue of our favourite magazine 'AmigActive~
> and was interested in the article about the performance of different
> modems.
>
> I recently bought a 'Twister Mk2' because I was not happy with the speeds I
> was getting from my IoBlix 1200 serial card. I could not get my Amiga to
> connect to the modem at 230400 baud and thought it might the the Ioblix
> that was causing the problem.
No, it's the modem. You'll be SERIOUSLY hard pushed to find an actual
modem that has a serial connection capable of greater than 115200.
Even the higher quality (US Robotics, Pace if you caught them before
they went tits up) modems will only do 115200.
> I am using a 3Com US Robotics X2 modem but I would like to know what is the
> best modem to use. Although it connects at 50666 and miamiDX reports that
> I can get 5.6Kb/sec when listening to a Shoutcast stream, it won't use
> 32kbps+ streams without breaking up every few seconds.
Wow.. you do have quite a quick connection there. You've got to be sitting
right on top of the exchange :)
Remember that any serial port speed is HIGHLY limited by the CPU in your
machine (although larger buffers on the ioblix (than the internal port), and
on the twister (than the ioblix even..) relieve the pressure, there is a limit
to the good they can do) and therefore what else is running at the same
time: MP3 decoding is going to sap CPU time from the serial port drivers,
and Miami.. also heavy web browsing (lots of maths intensive JS, or Flash,
etc.) will also knock the transfer rates for six if they carry on for long
enough
Simple explanation and example, the JS implementation in V3 is highly
umm.. I forget the word, it's been so long, but I think it's transput-bound
(or compute-bound?) in that it never has to wait for any external i/o to
complete - so it'll suck up as much cpu as your system can give.
The serial driver is highly input-bound in that it has to wait for buffers
to fill and for interrupts to fire before it does anything - hence it'll only
get CPU as and when some other part of the system gives up the time or
a higher priority serial interrupt fires.
> Is there a specific chipset used in modems that work best?
You're getting decent enough performance anyway. There's no way
you'll get better performance other than to, say, use a PPC native
serial driver on MorphOS (obviously not available for the Twister
at present)
Thanks
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