Bug(?) with the linux console

Bug(?) with the linux console

Post by Ra » Wed, 29 Nov 1995 04:00:00



This is just something I noticed somewhere around 1.3.2x, but never got
around to mentioning it. It was the release where basically all the
console routines were re-written and for some people, XFree86 was broken.
I'm using 1.3.45 and it still occurs.

I don't know if this is a bug, but if text is scrolling very quickly, it
will occasionally "jump" to the right and then back into place.

The following program displays this... just watch it run for a few
seconds.

#include <stdio.h>
#include <stdlib.h>

void main(void)
{
  while(1)
    printf("Hello World!\n");

Quote:}

Paul Fisher

 
 
 

Bug(?) with the linux console

Post by B. James Phillipp » Fri, 01 Dec 1995 04:00:00


Good, I'm not alone.

        I was going to post something about it.  Happens to me too.  When text is
scrolling along, there are occasional "wipes" of text at near light speed along
the right side of the screen.  I'm using 1.2.13 and an S3 card.  Console is on
80x25 mode.

--

Kickin' it since 1.1.59  =1B[1;35m  [www.ecst.csuchico.edu/~bryanxms]  =1B[0m
/* This message is not to be distributed across the Microsoft(tm) Network */

 
 
 

Bug(?) with the linux console

Post by Frodo Looijaa » Fri, 01 Dec 1995 04:00:00



Quote:>This is just something I noticed somewhere around 1.3.2x, but never got
>around to mentioning it.
>I'm using 1.3.45 and it still occurs.
>I don't know if this is a bug, but if text is scrolling very quickly, it
>will occasionally "jump" to the right and then back into place.

Happens to me too, but with kernel 1.2.13 and an OAK 067 video-card.
I too thought it was a hardware problem (OAK cards are not known
for their high quality). It is not a very big thing, but it isn't
as it should be either.
--
-----------------------------------------------------------------------
| Frodo Looijaard                   | It's better to burn out,        |
| University of Nijmegen            | Than to fade away.   (N. Young) |

 
 
 

Bug(?) with the linux console

Post by Michael F Gord » Fri, 01 Dec 1995 04:00:00



Quote:>I don't know if this is a bug, but if text is scrolling very quickly, it
>will occasionally "jump" to the right and then back into place.

I've seen this occasionally as well, but I just assumed it was a hardware
glitch with my cheap and * video card (Trident TVGA8900CL).  Which
video card are you using?

Michael Gordon
--
Politicians are like nappies, both should be changed regularly
and for the same reason - graffito on a wall in Yeovil.

 
 
 

Bug(?) with the linux console

Post by liuy » Fri, 01 Dec 1995 04:00:00



Quote:>Good, I'm not alone.
>    I was going to post something about it.  Happens to me too.  When text is
>scrolling along, there are occasional "wipes" of text at near light speed along
>the right side of the screen.  I'm using 1.2.13 and an S3 card.  Console is on
>80x25 mode.

Yup, same here.  Kernel 1.2.13 and a ET4000 card.  In 80x25 mode.
 
 
 

Bug(?) with the linux console

Post by Paul Fish » Fri, 01 Dec 1995 04:00:00



: I've seen this occasionally as well, but I just assumed it was a hardware
: glitch with my cheap and * video card (Trident TVGA8900CL).  Which
: video card are you using?

It's definately a software glitch. :) ... I'm using an ATI Mach32 VLB with
2MB vram.. it wasn't exactly an el-cheapo card when I purchased it. ;)

Paul Fisher

 
 
 

Bug(?) with the linux console

Post by Andries Brouw » Fri, 01 Dec 1995 04:00:00



when scrolling a lot of short lines one sometimes sees an image on the
right hand side of the screen):

: It's definately a software glitch. :) ... I'm using an ATI Mach32 VLB with
: 2MB vram.. it wasn't exactly an el-cheapo card when I purchased it. ;)

If I am not mistaken it is the phenomenon that the Start Address Register
is 16 bits long, of which first the high order part is loaded.
While scrolling, it is incremented by 80 for each line, assuming
you are using 80-char lines.
But 3*80 = 256-16. This means that if the high order part changes, and
the video hardware reads the SAR between updates of high order and
low order parts, then everything will be shifted back by 16 positions.

A bug? Maybe - it can be avoided by synchronizing with the vertical
retrace. But that would put a lot more knowledge about video hardware
in the kernel - generally a bad idea. Often such improvements break
on less standard hardware.

 
 
 

Bug(?) with the linux console

Post by Colten Edwar » Sat, 02 Dec 1995 04:00:00



: : I've seen this occasionally as well, but I just assumed it was a hardware
: : glitch with my cheap and * video card (Trident TVGA8900CL).  Which
: : video card are you using?
:
: It's definately a software glitch. :) ... I'm using an ATI Mach32 VLB with
: 2MB vram.. it wasn't exactly an el-cheapo card when I purchased it. ;)
:
: Paul Fisher

I've seen this as well with ATI Mach32 ISA with 2mb ram

                                                Colten Edwards

 
 
 

Bug(?) with the linux console

Post by Theofilu Andre » Sun, 03 Dec 1995 04:00:00




Quote:>I don't know if this is a bug, but if text is scrolling very quickly, it
>will occasionally "jump" to the right and then back into place.

It happens to me too. I'm using a SPEA-V7 VEGA PLUS card (ali2301 chipset)
and Linux 1.2.11. I noticed this also with older versions of Linux. This
behavior is not specific to Linux. I had an old XENIX on an i286 with a
Hercules graphic card (monochrome) and it did the same. Maybe this depends
realy on the hardware, not the software.
--
Theofilu Andreas

               -------------------------------------------------
                           Enjoy the science of Linux!
                       Genie?e die Wissenschaft von Linux!
               -------------------------------------------------

 
 
 

Bug(?) with the linux console

Post by Daniel Sim » Thu, 07 Dec 1995 04:00:00


I have a very similar problem on a much older kernel than yours (1.2.13)...

The other glitch that is reallly annoying is how the cursor displayed on the
screen doesn't match the actually cursor position. (Thus editing becomes
quite the exercise in dead reconing.) I thought this was only annoying but
then I started noticing that when the bad scrolling happened, it seemed to
be related to where the cursor was.

Anyway, it's still only a theory.

In case you care, I've got a Dell Lattitude XPI with the Cirrus Logic 7543
and some TFT display, and another XPi user has the same problem. But a
friend of mine with an Ascentia 950, which also has the 7543 and a similar
display does not have these problems (older kernel though, 1.2.8).

Any ideas?

Thanks a bunch,
--
Daniel Simms      "A common mistake that people make when trying to design

(415) 617-1258    ingenuity of complete fools" -Ford Prefect