BIOS extension for serial console?

Hi folks, sorry for the repost but I could not get help in any of the fora
I've tried so far.

F'up set to myself, I'll followup accordingly.

[ This is a repost of the following article: ]
[ From: Harald Milz <> ]
[ Subject: BIOS extension for serial console? ]
[ Newsgroups: comp.lang.asm.x86 ]
[ Message-ID: <br41mu$isp$> ]

Hi,

I have been doing some research on the topic, mainly because I would
like to add a serial console to my servers running Linux. As soon as
the boot loader takes over, they provide serial access themselves but I
would like to be able to fiddle with the BIOS setup or see if a server's
RAID adapter barfs at his harddisks. We're talking about older legacy
machines here which can't be upgraded to AMIBIOS8 for example. In my case,
it's a Tyan S1590S and an Asus A7V.

Research shows that there appears to be nothing available. Sooooo -
before I write something myself I would like to get some better idea how
the most popular BIOSes (AMI, Award/Phoenix) actually boot. This effort
makes only sense if legacy adapter BIOS extensions at C800 are found
and initialized very early in the boot process, in particular before
the BIOS enters the setup screen if requested.

I am a little bit confused about various sources which I've found. Some
say, adapter ROMs are found and initialized very early, e.g. before the
serial ports (!) (like <807hq7$kc1$>#1/1 posted here
in 1999i). Others like http://www.bioscentral.com/postcodes/awardbios.htm
say something completely different. And none of them clearly say whether
it's before or after the entry point for the setup. I would expect that
all BIOSes use the same or a very similar sequence of events because
they need to accomodate each and every add-on card with its own BIOS, and
they can't know if the extension cards need the serial port for example.

Ideally, I'd like to see everything including the memory check.

The question is whether a C800 ISA BIOS extension is the Right Thing
at all. Looking at various BIOS images with CBROM shows that there
are some more blocks in a compressed BIOS image. Can I add something
which will be initialized earlier than block C800, directly after the
VGA BIOS and the serial ports? The "master BIOS" of size 128k (Award)
seems to be the same in all cases. Modifying the BIOS proper would be
easy if one had the source code but ... ;-) Yes I know there's LinuxBIOS
but my boards are not supported by the project, and I don't want to dive
into the topic _that_ deep.

Any insight is appreciated...

Ciao,
Harald

 

On Wed, 10 Dec 2003 14:58:13 +0000 (UTC), Harald Milz

Wouldn't any number of KVM technologies available solve your problem
much more easily than fiddling with the BIOS?

RM

 

It is a question of bandwidth and cost. Serial can easily
be converted to TCP/IP with a cheap/old PC or sent over a modem.
Video/Kbd can be sent over TCP/IP, but the cheapest solutions are
in the 2000 Euro price range. Cheaper maybe with vga->TV->TV-grabber,
but what about the keyboard? Modem is out of the question.

I recently had some similar taks to solve (Linux CLuster), and
decided to do without remote BIOS access. Now it is KVM switch
for on-site debugging, booting via etherboot and remote power
switch for one test machine.

Arno

 

That's one thing that makes Sun gear so nice.

 

It's also a question of what your time is worth. The card I cited in
a post that went only to one newsgroup costs about $700US.

http://www.startech.com/ststore/itemdetail.cfm?ProductID=SV1105IPPCI&topbar=topbark.htm

I'm sure VAT would make it significantly higher in Europe, but I don't
know how much. To get power-on and reset access to an important
server in a closet somewhere as compared to paying that price, I know
*I* wouldn't be fiddling ROM code or jury rigging the VGA.

RM

 

which is far out of reach for my home network, as is the PC Weasel. AMI and
Intel have addon cards for that purpose as well but these are also above
$750. For a customer wanting to revive a legacy machine this may well be
more than what the machine itself is worth.

As far as the Startech card is concerned - thanks for the hint, I wasn't
aware of that. Unfortunately, the only distributor that is active in Europe
is Ingram Micro, and their web site is a closed dealers' community so that
I can't check whether they have it over here or not. If not, this is
not an option for corporate customers due to cross-atlantic support and
warranty issues.

And then, a new mainboard which does have serial console support per se
will be cheaper in many cases. The business case for such a card is flaky
at best. The PC Weasel at $350 for the PCI version is a borderline case
as far as price (and there isn't a European distributor either). What
I intend is a low-cost solution that admittedly will not cover all cases.
If you can or would use LinuxBIOS, you could use such a solution as well.

Well that's a matter of taste. Hacking is fun. Otherwise things like
Unix or Linux would never have existed. )

But anyways - I would rather not dive into philosophical discussions. I am
looking for technical help

While we're at it - I had a look at the BIOS of my Matrox G200 card. In
DOS DEBUG, I could "d c000:0" or "u c000:3" just fine. But - I could
not write the block c000:0 32K to a floppy directly using INT 21h,
AH=40h. Strangely, all that came up were FFh bytes, and 32K of them. I
could, though, copy the block to another memory location using lodsw,
stosw, and write it to a floppy from there. Any idea why this is so? I
mean we're talking about x86 real mode here, and the idea that there
may be some sort of copy protection seems very weird to me.

Legacy PCI cards with socketed DIL ROMs are ten a penny on Ebay - many AGP
cards have socketed PLCC ROMs instead. Which is also fine if you buy or
make a DIL-PLCC adapter. I'd use EEPROMs for the job because they can be
reprogrammed without UV erase...

Without hving looked at other VGA cards - is it safe to assume that their
BIOS chips are 32K only, and real mode, or do they play dirty tricks like
compressed images etc.? The card's I've seen on photos have 28pin DIL
sockets, and the maximum for 28 pins is 1Mx8 (27C801) AFAIK.

 

You can't put a dollar (or euro) sign on those rewards. We all have
different skill sets and time constraints.

RM

 

The floppy controller is one of the last devices using legacy dma, and the dma
controller simply cannot access expansion roms on your machine.

For development a 62256 ram chip would be a better choice. Load it, reset and
try. If your computer hangs, turn off and on an try again.

Bios extensions can be up to 64k and start with 55 aa (length/512) on a 2k
boundary. VGA biosses aren't compressed.

I've got a Powrtwell comunication appliace which has a bios with a serial
console. I don't know how they do it - it also works with direct video ram
access.

Mit freundlichen Grüßen

Dipl.-Ing. Frank-Christian Krügel

 

With a 3V Li cell or so, yes. I've still got some of them left.