Re: [9fans] What a poor VGA support !

[Agnelo de la Crotche <agnelo.geo@yahoo.com>]

Agnelo de la Crotche wrote:

> presotto@plan9.bell-labs.com wrote:
>
> > > Simple, because it is supported by the 28 other
> > > operating systems I managed to install on that machine.
> >
> > My interest is clearly piqued.  What are those 28 OS's and
> > what to you use to boot them all?
> >
>
> As long as you're asking 'how?' and not 'why?' ....
>
> - 6 DOSez : MS-DOS, PC DOS, Open DOS, DR DOS,  PTS DOS, Free DOS
>     - 6 Windozes : 95, 98 , ME, NT, 2K, XP
>     - 3 BSD : Free BSD, Open BSD, Net BSD
>     - 2 Linux : Debian, Suse
>     - 2 Unix : SCO, Solaris
>     - 1 Minix
>     - 8 others : Hurd, BeOS, QNX, OS/2, AtheOS, VsTa, Netware, Amoeba
>     - 1 Plan9
>
> on 2 IBM IDE 40 GB harddisks,  a single AMD K6-2 500 MHz CPU and 512 MB Ram.
>
> Basically I use 3 bootmanagers :
>     - xfdisk ( http://www.mecronome.de/xfdisk/ ) in the MBR of the first HD
>     - the XP bootloader in the bootsector of a primary FAt 16 partition ( <=
> 256 MB )
>     - Grub in a bootsector of some logical partition.
>
>     and some small shell scripts and batchfiles calling utilities (like dd)
> to rewrite
>     the partition tables when necessary.
>
> As a rule, I never use a floppy, emulator or virtual machine. If I cannot
> boot an
> operating system the simple way from the harddisk, I don't install it.
>
> It is not as complicated  as writing video drivers and probably much more
> useless, but
> having spent the last couple years playing around with bootsectors, hard disk
>
> partitions and 'ennemy' operating systems, I would probably have enough stuff
> to
> dedicate a website to the subject, although there are already plenty of
> those, but
> I've never heard of anybody getting as many bootable OS.  The only problem is
>
> that I need at least  3 hours of sleep.
>
> You can easily figure out that the greatest difficulty has been to get the
> widest compatible
> hardware components for all these OS.   Replacing a video card is a great big
> deal
> for me.
>
> >
> > > But , please, tell me, because I'm curious : Why is it so difficult, so
> > > impossible to add some kind of minimum VGA support  ?
> >
> > We used to have minimum support, i.e., 640x480x{1,2,4}.  Those modes are
> > standard and normally grey scale.  You can use a color map with them
> > but 16 or fewer colors doesn't make for great viewing, red letters on
> > a blue backround was my favorite headache producer.
> >
>
> Even under DOS I can get some graphic based applications working
> in a reasonnable resolution. ( which doesn't mean that I use them !)
>
> >
> > We nuked support for the standard modes because
> > a) it was very odd to implement especially after we changed
> >   graphics models.  It doesn't really fit the
> >   model of a frame buffer.  Instead you had to do odd things
> >   to write the different bits to diferent planes.
> > b) it was made clear to us that supporting 640x480x4 grey scale
> >   was so inferior to what people wanted that it wasn't worth the
> >   effort.
> >
> > All other modes are non-standard, i.e., different from card type
> > to card type.  There are a smaller number of VGA chips than cards
> > though even that number is unwieldy.  How the differenty
> > card manufacturers map the chips and plug them together varies.
> > Often the only extra info we have to know about a card is how to
> > recognize it.  PCI is helping there though in the past we had to
> > look at the onboard BIOS and look for patterns; half of /lib/vgadb
> > is just trying to figure out what's there.  If you wc /sys/src/cmd/aux/vga
> > you'll see that the ammount of code per chip type is pretty small
> > (often with an equivalent amount in the kernel to support
> > cursors and such).  However figuring out that code is hard:
> >
>
> I've already tried, read, compared, posted, modified all that ( without
> knowing what
> I was doing ) last year, with the only result of destroying a monitor.  I'm
> not
> complaining about that, I was aware of the risk.
>
> >
> > - documentation is usually poor or non-existant.  Drivers from
> >  more popular OS's (or X) are often the only documentation
> > - Some registers bits lock out other registers; just reading the
> >  settings used by windows and rewriting them back is usually
> >  impossible.
> > - setup requires writing values into MANY registers, most of
> >  which are different from chip to chip.  The values are dependent
> >  on clock speed, bit depth, screen size, and chip version.  Just
> >  getting them working on one machine doesn't ensure they'll work
> >  on another.  In some cases it takes futzing with a number of
> >  machines and board revs to get a `stable' implementation.
>
> What I found particularly annoying and frustrating is that it almost works.
> Almost !  I have already discussed that issue and probalby other people
> did as well.  You know : the problem with the overlapped screen !
> The chipset is identified,  because different ATI Xpert use the same
> chipset and so have the same BIOS signature. I was told that they run at
> different clock speed.
> Even if what I got to  see, about 2/3 of  windows is sufficient for the
> installation,
> you cannot think of starting anything  with it.
>
> >
> > Our most popular laptop is the T23 (because of a company deal with
> > IBM) and we set it up by being careful not to touch too many registers
> > since we have no idea what the LCD extension registers do.
> >
> > In our group, we have one person, jmk, who sepnds a considerable amount
> > of time just getting the cards we have working.  However, that's
> > in addition to what he's supposed to be doing, not what he's paid
> > for.  Some of the community is also nice enough to send us the /lib/vgadb
> > info + drivers to get other cards working.
>
> So did I.
>
> >  However, because the
> > Plan 9 distribution is a 'free time' effort at the Labs we can't
> > aim one person to doing full time VGA support.  If the community
> > were larger, we'ld probably get enough contributions to cover a
> > larger percentage of the cards or if Plan 9 were actually popular
> > we might be able to get manufacturers to write drivers.
> >
> > It would be useful if the manufacturers could get together and
> > come up with another VGA standard so that we would waste less
> > time and angst.  However, there's no real motivation for this.
> > To first order, there's only one OS for PC's, and to second order
> > only two.  It's not that hard for a manufacturer to put together
> > drivers for their new board for 2 OS's.
>
> Obviously if they were humanists, they won't be manufacturers.
>
> >  I'm pretty impressed that
> > there are 26 others that manage to support all cards.
>
> As I said Plan9 is the 'only' OS which doesn't work like it should.
> I've been coming so far with that operating system to write a
> bootmenu and set the default to 'no vga'. So at least, it boots
> and opens a console and I can count it as the 29th.
>
> >
>
> > Besides, if you ever got your ATI Xpert (Rage Pro) working,
> > we'ld have to go through this conversation again explaining why
> > we don't have a web browser worth using.
>
> Since I (almost) never get up, I keep trying regurarly ...

What a funny mistake ! You would have read 'give up' instead.

>
>
> agnelo.