🚀 go-pugleaf

Tod Masters (masters@ozemail.com.au) wrote:
> 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!


In general it does.  DOS software tends to disable interrupts excessively.

--
Best regards,
John  <JNavas@Netcom.com>