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SubjectRe: Winmodem support, some performance tradeoff estimates
On Sun, Aug 16, 1998 at 12:34:36PM -0700, Adam J. Richter wrote:

> I have seen a number of less technical linux advocates get
> defensive about the fact that the only soft modem drivers for the
> Linux kernel are currently the binary only driver for some 2.0.x
> kernel on the US Robotics web site and the radio sound modem drivers.
> [ ... snip ... ]
> The latest revision of WebTV runs on a 56k soft modem in the
> background on an 8MHz MIPS R4000 processor. Let's say that this
> means the performance of using a soft modem is about 8 Pentium MHz,

The problem may be more one of latency than of raw CPU power. If the
DSP calculations only require a relatively few cycles but require them
nearly immediately and at frequent intervals, this would boost the CPU
requirements. Add in the delay caused by, e.g., a disk driver that
leaves interrupts masked for a considerable length of time, and the
danger of sync loss increases.

> The situation is likely to tip even more in favor of soft
> modems in the future, since CPU prices have been on a much faster
> downward curve, and we can expect fewer economies of scale and less
> intense competition for future market for hard modems.

I'd expect the price of DSPs and related modem parts to continue to
drop, if not so quickly as Pentiums. Once the price of a DSP drops
low enough, i.e., to less than the cost of the cardboard box that the
modem gets packed in, there should be less motivation to sell
marginally functional half-of-a-modems. As soon as a large number of
folks start returning these things for lack of proper Linux or NT
drivers, the cost of a DSP chip could well become less than the cost
of handling returned merchandise.

-- John Kodis.

PS: interesting analysis, in spite these quibbles.

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