modem speeds and external modems and 386sx/8
On Thu, 14 May 1998, Bob Nielsen wrote:
> On Thu, 14 May 1998, Breathnach, Proinnsias (Dublin) wrote:
>
> > c) If you have a 386SX and an external 56K Modem you will NOT get a
> > better connect than 9600bps due to the fact that the computer will only have
> > an old INS 8250 UART. - even if the modem had a UART (which would be a
> > redundancy) you will only get the throughput of the *slowest* part of the
> > system.
> > As always I'm open to contradiction on any points made here :)
>
> Well, as long as you asked--
>
> I've never seen a 386sx with an onboard serial port, but have successfully
> used serial cards with 16550A uarts at rates above 9600 baud in a 386sx,
> as well as a 286. IIRC, only 8086/8 types are limited to the 8250, and
> that is only because of a bug in the chip design which was corrected in
> the PC and XT bios, making them incompatible with the 16450 or 16550.
we have a 386sx/8mHz (AT class machine). we are currently using a
"2serial/1par" (16550A UARTs on /dev/ttyS0 and /dev/ttyS1) with 2 USR
Sportster 33.6kbps modems. They are connecting at 31.2kbps DCE and
115.2kbps DTE. And we have had no problems with line speed at all. we
do tell setserial to set the device flag spd_vhi tho? we think the 1
step down is due to GTE's lines. we also have a 4 port serial card
with 16550A's and have on /dev/ttyS2 a 14.4kbps USR Sportster external
that connects at 14.4kbps DCE and 57.6kbps DTE (its setserial uses the
flags irq 10 port 0x3E8 ^fourport spd_hi), /dev/ttyS3, serial mouse
(port 0x2E8 irq 10 ^fourport), /dev/ttyS4, dedicated vt220 serial
terminal (port 0x1A8 irq 10 ^fourport) and /dev/ttyS4, serial port for
apc BackUSP Pro 1000, (port 0x2A8 irq 10 ^fourport). these all work
fine for us.
Fuzzy
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