Date: Mon, 14 Apr 1997 13:36:20 +0800 (GMT)
From: Orlando Andico <orly AT gibson DOT eee DOT upd DOT edu DOT ph>
To: John Beppu <beppu AT rigel DOT oac DOT uci DOT edu>
cc: djgpp AT delorie DOT com
Subject: Re: HELP: vesa 2 & linear framebuffering
In-Reply-To: <5ieqiu$m9t@news.service.uci.edu>
Message-ID: <Pine.SGI.3.93.970414133438.16352A-100000@gibson.eee.upd.edu.ph>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII

On 9 Apr 1997, John Beppu wrote:

>   I also have a dx2/66 and a vlb cirrus logic 5428.  If you have
>   more than 16MB of RAM, your cirrus logic will turn stupid on
>   you and won't know how to map its memory to a linear frame
>   buffer for your use.  According to the documentation from
>   XFree86 (an X Server for Linux), the cl5428 likes to map its
>   LFB at somewhere around 14MB or 16MB.  I'm not sure about the
>   exact details, but the main point was that system memory
>   overlapped with where the LFB was mapped to, and that's apparently
>   not a Good Thing.

Most (all I've seen) Cirrus VLB cards map their LFB to somewhere high --
78MB for some, 4000+MB (near the 32-bit limit) for others. True, there are
Cirrus cards that map to 14MB, but those are generally ISA cards.

You could try running UniVBE, it prints out where the LFB is mapped to. If
it indeed maps to somewhere overlapping your main memory, tough luck --
you'll have to disable the LFB and live with VESA 1.2 only..


-----------------------------------------------------------------------
Orlando Andico                               IRC Lab/EE Dept/UP Diliman
email: orly AT gibson DOT eee DOT upd DOT edu DOT ph          http://gibson.eee.upd.edu.ph
   "There's an obvious attraction to the path of least resistance.."