Subject: Re: FW: 2 Problems
To: Gunnar Helliesen <>
From: Brian D Chase <>
List: port-i386
Date: 11/15/1998 00:43:04
On Sun, 15 Nov 1998, Gunnar Helliesen wrote:

> FYI, in case some of you don't follow port-i386.
> Those of you who have opinions on this better voice them now...


> -----Original Message-----
> From:
> [] 
> Sent: Thursday, November 12, 1998 9:00 PM
> To:
> Cc:; port-i386; tech-install;
> Subject: Re: 2 Problems 
> said:
> > Charles noted to me a while back that wscons was slow because it only
> > processes one character at a time.
> I remember a mail from Charles where he blamed slowness to two things:
> -one character at a time, as you say
> -scrolling by copying
> Some profiling showed that the scrolling did indeed use up a significant
> fraction of CPU time (not top-ranking, still less than bz^H^Hmemset, but
> worth optimizing). Character output was much less.  So I changed the
> scrolling to use offset registers on VGA.  The reason that the character
> output is done this way is that the terminal emulation module interprets
> the incoming (8-bit)  characters and spits out indices (32-bit) into a
> potentially larger character set, keeping state about charset switching
> control sequences.  It has to touch every incoming character anyway, and
> even if it did try to cache a row it would have to transform each
> character into the 32-bit font index and put it into a separately
> allocated array.  I'm not convinced this is worth the effort. 
> > Any idea if we can fix that problem? 
> For me, this is not a problem. As long as the vax people don't
> complain...

Well, we may if the wscons performance is abysmal.  We don't have a lot of
spare processing power laying around to deal with inefficiencies.  Based
on the above, it seems that scrolling is the greater of the two issues to
be addressed.  Is there anything which can be done to optimize scrolling
in a machine independent way?

Brian "JARAI" Chase | | VAXZilla LIVES!!!