1237a55379a4
tech



Hello Jim - 

--8<--cut 

JH> You say your 486 had a fast UART and the Pentium only has
JH> an 8250? I'm surprised. I think before I tried doing a UART
JH> chip-swap (if I could even _find_ a separate UART chip),
JH> I'd consider looking for a serial card with 16550 UART(s),
JH> and disabling the mainboard Serial ports. 

If the machine had an internal modem orginally I can imagine
how they decided the serial ports did not need a true 16550A. I
would go with an internal modem myself even though it is nice
to have an external around for testing etc. of other systems. 

JH> In any event, if what the Pentium board has is only 8250 or
JH> compatible/emulated, I think no need to hurry to buy an
JH> external 56K serial modem, as TBOMK the 8250 won't support
JH> that speed. Corrections welcomed, if I'm wrong. 

Seems like 'baiting' here to me but ... 

At the speed of that CPU I would guess at the very least the
UARTs are 16450s or even 16550s (no 'A')? This would be shabby
business practices IMO but I can imagine some manuf did try to
sneak the plain 16550s through to save that 'nickel' they
squeeze so very tightly. :-\ 

AFAIK the 8250, 16450, and 16550 (no 'A') are more or less the
same in terms of performance. 

MSD.EXE from Wayne's W31 OS should tell him what they are? 

I've tested both the 8250 and 16450 and they will support 57600
using a null modem cable between the serial ports and GSZ as
the application software doing the transfers with zero resends.
If, as is the prevailing wisdom, a locked 115200 was attempted
then all bets are off as these UARTs might error out frequently
which means any compression to achieve random speed 'bursts'
wouldn't happen for the 56k modem which is never really at 56k
anyhow. We all know that the FCC has limited us to 53k at most
and typical connects are 40-44k to the ISP using POTS lines? 

When using a browser these speed bursts are handy for the HTML
(text) portion of the webpages, for downloading files not so.
Most application software files are compressed into an archive
and maintain a certain average speed thoughout the entire
download. 

This slight variation when browsing may not be significant? 

Judging by server stats from my music webpage almost 50% of all
who frequent that webpage are on DSL connects which is another
excuse for neglecting to put in 16550As? Serial ports are
dropping in significance lately. 

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