From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <38DA42E5.2B80E717@ncal.verio.com> Date: Thu, 23 Mar 2000 08:14:29 -0800 From: Henry Worth MIME-Version: 1.0 To: linuxppc-dev@lists.linuxppc.org Subject: Re: PB2000 (pismo) install feedback Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: This is the old RAMDAC problem of trying to write to the pallete registers too soon after setting the index, complicated by an integrated chipset and probably PCI I/O write posting as well. It results in the display having about 8 vertical bands and a big bright spot alternating between them. It also makes the bubbles in the layers of film making up the LCD show through so that it looks a bit like when a frame of motion picture film burns in the projector. It's very timing sensitive, a slight rearrangment of the code eliminated the "burnout", but didn't fix the ongoing offb colormap problems. Adding a small delay between writing the index and the palette value fixed the colomap problem. I rearranged the code to just set the index once and then use the palette index register's auto-incrementing to avoid the index write and delay in the loop, and that worked as well. I think Ben is planning to use a read back of the index register to ensure the write is posted and and give enough of a delay. Does anyone know if any of the ATI chips don't have autoincrementing of the palette index? That's been a fairly standard feature of RAMDAC's for a long time. So I was a bit surprised to see the frame buffers explicitly setting the index on every iteration, especially since the race between writing the palette index and the data has been a common problem for a long time. Henry ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/