Internal modem faulty?

Our cursed "late 2004" G5 has a replacement modem (the original one had been lost during repair), and now I notice massive problems with the internet connection. An old external, serial Elsa modem on a G3 works fine at the same telephone socket.

The symptoms:
While the Elsa connects with usually 42k up to 46k, the internal one tries to connect with 45k to 50k.

In case it had connected with 50k, the connection is fast and stable for about 30 seconds, then the modem disconnects.

In case of 46k the transfer rate is slow (about 3kByte/s), and it goes down or totally stalls after about 1 minute.

In case of 45k the transfer rate is fine for the first 1-2 minutes (about 4kBytes/s), then falls to 1-2k and finally to 1k -0.5k. So the internet connection is usable for about 1 to 2 minutes.

I do not know if this behaviour has been the same before, i.e. with the old modem. It could result from the modem trying to connect with a too high speed. Can that be limited in some way, i.e. to maybe 40k/s? Or does anybody have another idea?

Mac OS X (10.4.3)

Posted on Dec 30, 2005 5:32 AM

Reply
1 reply

Mar 6, 2006 8:05 AM in response to Andreas Kromke

Addendum:

Limiting the modem to V.90 instead of V.92 did not improve the situation.

Exchanging the modem may have improved the situation a little bit, but not really. The transfer rates are still low , compared to those of the old Elsa modem.

It seems that the internal G5 modem is called "UbiSurf SM56 Software Modem"; this kind of modem is also known as "Win-Modem".

See http://manuals.info.apple.com/AppleSupport_Area/Manuals/other/UbiSurf_AT_CommandSet.pdf for a description of the AT command set.

By editing the modem script it should be possible to limit the modem connection. Unfortunately only the limit to 33,6 kbps worked, so there are only two alternatives, maximum speed or 33,6 kbps.

With 33,6 kbps the transfer speed and the connection seemed to be a little bit more constant resp. stable, but 33,6 kbps is not really a nice speed.

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Internal modem faulty?

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