[mdlug] old machine modem question..

[Adam Tauno Williams]

On Sun, 2012-05-06 at 14:01 -0400, Aaron Kulkis wrote: 
> Carl T. Miller wrote:
> > *****-otakurider wrote:
> >> Anyone have stuck deep in there brain the setup notes for a ThinkPad T22
> >> WinModem setups?  Did some goggling and the links seems to be broke to
> >> configure it
> > My only notes for WinModems consist of the suggestion
> > to purchase a USB modem.  Keep that in mind for plan B.
> Yes.  External modems  *must* be real modems, so they are always
> a good value.

For a laptop PCMCIA modems can be found at the scrap yards really cheap.
I have a single-slot height Dell 28.8k PCMCIA modem I bought for ~$5
several years ago.  It works great and is a traditional serial device.

> The only problem with USB stuff is that it is all done
> by polling, rather than interrupt driven -- i'm not sure
> which as the worst CPU overhead -- polling on USB or
> the CPU having to play DSP(digital signal processing)
> games because lose-modems don't have proper DSP chips
> inside them.

Eh, this isn't really true.  USB is polling and half-duplex.... but it
is polling and half-duplex *in hardware*.  The system CPU does not
necessarily have to be involved in the polling.  And while some latency
is introduced it is introduced on the USB bus and in everything but the
most ancient of chip-sets the latency is still far below what would
effect a buffered UART even when operating at very high speeds.
Software can subscribe to interrupt's for USB attached devices.
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