Re: High-speed serial link problems

[Petr Stehlik <stehlik@cas3.zlin.vutbr.cz>]

On Wed, 11 Jun 1997, Mario Becroft wrote:

> Hello,

Hi Mario,

> I have been following the recent discussion regarding high speed serial
> ports under MiNT, but none of it seems to relate exactly to a problem that
> I am having.

After reading your long mail I must tell you that I have experienced the
same problems - low transfer speed @ 115200 bps, serial problems with
N.AES.

> I have my TT030 running MiNT connected via a null modem cable a IBM
> compatible (with DOS). The IBM compatible is intended to act as a terminal
> for the TT

I have my Falcon040 connected with Linux on an IBM. I've tried just ftp. I
wanted to set up nfs, but with the serial problems it was not possible,
unfortunately.

> Data would transfer across the link without any noticable problems at
> 115k2, but soon I discovered that things went wrong when large amounts of
> data were being transferred.

yep. Ping works here, but ftp stops.

> fast as it should. For example: transfering data from the TT to the DOS
> machine via zmodem (using sz) I got 2199CPS, which is clearly too low.

yep, similar situation here.

> 9230CPS - much closer to what you would expect. I then started N.AES on
> the TT, and was surprised to find that TT->IBM transfers dropped to
> 1944CPS and transfers IBM->TT went wrong badly, with many errors
> appearing. 

exactly the same here.

> It seems that at this speed the TT just could not keep up, when
> N.AES was running. But surely the TT should be able to handle transfers 10
> times faster, or more, than the ones I am attempting.

Yes, I agree. BTW, my machine is about 7 times faster than a TT, but has
the same problems - quite strange, isn't it?

> How could the AES,
> using (according to top) under 4% processor time, cause the TT to become
> unable to handle 9000CPS throughput? Also, when doing this transfer, I
> found that the TT responded extremely slow, as though the transfer was
> taking up all the processor time.

yes, and yes, and yes. Still the same story.

> Questions:
> 
> * Why do I get only 2200CPS throughput sending from the TT? (While I get a
> better, but not perfect, 9200CPS receiving.)
> 
> * Why does the TT seem to struggle to cope with 9200CPS, and fail
> altogether when I have a simple thing like N.AES using only 4% or so CPU
> time?

I ask myself the same questions. I don't know the answers. I just hope
somebody will answer them.

Petr
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