Date: Mon, 16 May 94 19:03:59 -0400
From: dj AT ctron DOT com (DJ Delorie)
To: iclone!ctm AT cs DOT unm DOT edu
Cc: djgpp AT sun DOT soe DOT clarkson DOT edu
Subject: Re: Serial Port status?

> First off, I assume the reason for the dedicated TSR is one of  
> performance.

Nope.  asy was done long ago, before you *could* trap real-mode
interrupts in protected mode.  You can now use the DPMI services to
trap all interrupts, real and protected, with your own 32-bit handler.

>              With DJGPP 1.11, I should be able to use INT 14 and get  
> serial port access directly, but presumably I won't get as good  
> throughput as I would by using aeasy.

Int 14 is NOT interrupt driven, and you will lose characters under
heavy load.  If you spend most of your time in protected mode
(i.e. most interrupts happen there), trapping them yourself in
protected mode will provide the best response time.

>                                       However, aeasy appears to only  
> affect reception, not transmission.

Correct.  Transmission does not need to be interrupt-driven to prevent
character loss.

> Q1:  Does that mean that using aeasy will allow very fast  
> transmission, but slower reception?

No.  The purpose was to provide an interrupt-driven interface.
Performance was not a concern, and I don't think performance will
differ much, except that interrupt-driven systems will not lose
chracters.