🚀 go-pugleaf

Justin Hawkins <jhawkins@tardis.apana.org.au> wrote:
 >I recently upgraded to a DX2/66 (from a 386SX-25). This was a
 >motherboard only upgrade, so I still have the (crappy) old IO card
 >installed (with 8250 UARTS). In DOS I find that now file transfers
 >at any speed have errors, whereas before, I didn't. I tracked it
 >down, it turns out that whenever disk IO occured, the file transfer
 >would get an error. In OS/2 this does not occur. Downloading to a
 >RAM disk under DOS allows error free transfers.
 >
The 8250 is a pretty simple UART and doesn't do any buffering in hardware - if
your application doesn't read an incoming character out of the read buffer
before the next character is complete, you get an overrun error.  Usually low
speed transfers work OK, but the 8250 just can't hack today's high speed coms
(I think 9600 bps was the limit for an 8250 on the original PC bus).  The 16450
and 16550 both have hardware receive and transmit buffers (I think the 16450
has 8 character buffers - don't know about the 16550).  This gives the software
more time to do other things between interrupts.

I can't explain why it doesn't happen under OS/2 - I can't believe OS/2 has
better interrupt latency than DOS!

 >I shrugged it off as a peculiarity of my motherboard+controller (it
 >didn't bother me since it didn't manifest itself under OS/2) until
 >my friend upgraded his motherboard (from a 386DX-40) to a DX2/66 as
 >well, and the same thing happens.
 >
 >What causes this? I suspect it has something to do with the way DOS
 >does it's disk IO. Is there any way of curing this under DOS, as my
 >friend won't be able to upgrade his OS for a while yet.

Try getting a serial port card with 16550s installed.