Biosutil V1.1
InfoMatrix Bios utilities for the AT BIOS.
Brad Gibson Copyright (C) 1990 by Secret Software
A division of InfoMatrix
InfoMatrix
1515 Hogansville Rd #83
Lagrange, GA 30240
InfoMatrix BBS:404-845-1714

______________________________________________________________
NOTE
The use of all trademarks, copyrights or other protected
names or symbols in this document are for reference only, and
contain no inference.
______________________________________________________________

Biosutil is Copyrighted (C) 1990 by Secret Software, a
division of InfoMatrix, it is not in the public domain and
it is not free. This is a shareware product, registration is
$12.00 and should be mailed to the address above if you find
the program useful. It is not crippled in any way, and we're
not going to send you anything if you register it, but if you
use it and want shareware to continue, then send the
registration. We will offer technical support and guidance to
all users who call us with a registration number.
______________________________________________________________

INFOMATRIX WILL NOT ACCEPT LIABILITY FOR ANY DAMAGE DONE TO
HARDWARE OR SOFTWARE AS A RESULT OF THE USE OF OR INABILITY
TO USE THIS PROGRAM OR INFORMATION IN THIS DOCUMENT, NEITHER
WILL WE BE HELD LIABLE FOR DAMAGE THAT OCCURS INCIDENTAL TO THE
USE OF OR INABILITY TO USE THIS PROGRAM, OR THE INFORMATION
IN THIS DOCUMENT.

Many of the changes and modifications suggested are very
technically detailed, and working at that level always
entails a certain amount of risk. We have tried to make
this as error-free and safe as possible, but anything you do
to your own computer is your own responsibility.
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What the BIOS utilities will do:

These BIOS utilities will perform three functions critical
to the duplication or modification of the AT BIOS:
1.) Copy the BIOS from ROM to a file. (BIOS.FIL)
2.) Re-calculate and update the checksum of a modified BIOS.
3.) Prep the file for burning to new EPROMS.
It will also allow you to view the built-in drive table parameters
in your BIOS once you have copied the BIOS to a file, and you may
also add your own custom drives to the file's drive table before
burning the new BIOS EPROM.


Why would you want to do this?

Let's state for the record that WE DO NOT INTEND FOR THIS
PROGRAM TO BE USED TO MAKE BOOTLEG BIOS COPIES!!! To do so
would be illegal and unethical. So why would you want to use
this software? Well, we have found that the old AT's still
have a lot of life left in them and that they can be brought
into the modern world through the addition of a few nifty

mods which we will discuss in detail later, the most
important of which is a bigger hard drive. The original AT
had a full-high 30 MB clunker in it and the new 40 - 80 MB
drives, and even the SCSI's and ESDI's would make an AT
faster and a lot more useful. One big problem you run into is
that the old AT BIOS does not support the new, large drives
in their setup drive tables. Those numbers are easy to add to
the 'BIOS.FIL' file that Biosutil creates for you. You may
then re-calculate and update the checksum, prep the files for
EPROM and burn new, more capable BIOS chips very
inexpensively! Of course there are alternatives to this: you
can just buy new BIOS chips from somebody like AMI (they make
VERY nice ones.) or you can use something like Ontrack's Disk
Manager to format the drive and use the config.sys driver,
but God be with you if you have to boot from a floppy and
forget to include the driver! The portion of the drive
partitioned above 32 MB will be inaccessable until you boot
with the driver. We think this way is much more economical,
and was much more fun for us. You can also make BIOS copies.
In case your BIOS PROMS ever crap out someday, you can just
pop the copies in and be back in business.


A brief rundown on the AT BIOS:

The AT BIOS is a unique little beastie, with a couple of cute
tricks and traps set for the intrepid BIOS-buster. First off
the basic structure of the bios is very strange. The BIOS
inhabits two 32K PROMS in your AT motherboard, component
reference designators U27 and U47. The total size of the BIOS
is 64K, but it is dispersed among the two PROMS in a
staggered arrangement where U27 contains the EVEN addresses
and U47 contains the ODD addresses. You can see this if you
run DEBUG then type D F000:0000. You will see something
like this "CCOOPPRR. IIBBMM 11998844" which is the copyright
notice, and can be seen intact in the even set as well as the
odd set.
The next item of interest is the ROM checksum. The last
byte of the BIOS is a checksum value of all the bytes added
together MODULUS 100H (which means that if you add all the bytes
plus the checksum the result will be evenly divisible by 256.
The tech manual said "MOD 100h" but we figured it out anyway). The
problem this causes is that the checksum is wrong if you have
modified some part of the BIOS and not the checksum. The second
sub-test of the first POST (Power On Self Test) test is a ROM
checksum check, and if the checksum is wrong is sends an HLT
(halt) instruction to the processor without so much as a
fare-thee-well to the user.

Now here are some facts that Big (blue) Brother does not
want you to know about your AT:
* There is a "speed bump" in the BIOS that detects whether
the processor is running faster than they intended for it to (as
in somebody installed a speedup kit...) and it will actually shut
down the processor if it's running faster than the BIOS says it
can. Naughty computer!
* There was a field replacement unit for the full-high AFH
controller in the AT that was actually an upgrade, but it was only
being installed when the service reps had complaints about the old
ones not working so well.
* There is an "AT UPGRADE" BIOS that has never been
released. With it you could install a few parts, and run the
machine much faster. It eliminated the "speed bump", provided for
bus settle time at the higher clock rate, included drive table
entries for some of the more popular large drives, allowed booting
from drive B, and other features that an AT sure could use. This

'turbo at' required the use of the newer floppy/hard drive
controller mentioned above in order to work properly. This
upgrade deal was supposed to come out right before the PS/2 hit
the market, but apparently somebody thought that the upgraded AT's
might sink the new products (like the AT technology (ISA) and EISA
clones are going to).
* There is an new "ADVANCED DIAGNOSTICS" that was not
released at the same time the upgrade kit wasn't released. It
helped handle all the improvements.

How to use Biosutil:

Ah, here's the fun part. In order to use this program to
create your very own BIOS chips you are going to need an

EPROM programmer ("EPROM burner" to you streetwise hacker
types), and some EPROMS (32Kx8 28 pin dip, the part number is
usually 27256 or 27C256 or some variant of that). The EPROMS
are pretty easy to find. The EPROM burner can be had from
lots of computer suppliers, for example JDR microdevices has
one for about $130.00, if you don't have access to one.
I will make the next statement one time: THIS PROGRAM HAS
ONLY BEEN TESTED WITH THE AUTHENTIC AT BIOS's, IT MIGHT WORK ON
OTHER BRANDS, AND IT MIGHT NOT. EITHER WAY INFOMATRIX WILL NOT BE
LIABLE FOR ANYTHING YOU DO WITH THIS PROGRAM, OR ANYTHING IT DOES
TO YOUR COMPUTER. USE IT AT YOUR OWN RISK.
The first step in the process is to copy the bios from the
existing ROM into a file. The first part of the program will
create a file called "BIOS.FIL", which will contain the BIOS data.
This is the file you can play with if you like. The only really
useful and safe changes you can make to the BIOS is to add drive
parameters to the fixed disk tables. The Biosutil Menu has two
options that will allow you to view the drive tables for the BIOS
file you have created and then add another drive type with your
custom parameters (if whoever wrote your BIOS hasn't used them
all).
The second phase of the process is the updating of the
BIOS checksum IF you modified the BIOS! If you didn't, you may
skip this step. IF you did modify the BIOS, this step should
properly update the BIOS checksum. Here is where some
incompatability problems may arise. I have run this on several
kinds of BIOS, and the fact is that not everyone uses the same
process for the checksum. For that matter, some developers may not
use the checksum at all. The AMI BIOS that I ran came out wrong,
and a couple of other kinds. I know for a fact that it works on
the genuine AT BIOS, beyond that your on your own. Hey, they're
Eproms, you know? experiment and figure out how to make it work if
this program doesn't get it right!
Finally the third section will create the split files for
you, which will be the actual data that is burned into the
EPROM's. Depending on your EPROM programmer, you may have to
convert the files to another format. We have included a formatter
that will creat Intel Hex object format files, which are very
popular for EPROM programmers. Most of them will use this or
straight binary (the raw files).

In summary, remember that you may modify the BIOS file, or
just use it to make copies of the BIOS ROM. That is a simple
process of letting Biosutil run through all three of it's copying
processes sequentially, then formatting the EVEN.FIL and ODD.FIL
for your eprom programmer, and burning the chips.

I hope this program is of some use to somebody, as much hard
work, blood, sweat, and failed attempts to copy the BIOS
went into it's creation. Once again, don't use the program
to make illegal copies of your BIOS, but rather as a tool to
help you upgrade your machine, or safegaurd against a PROM

deteriorating.

The IBM technical reference manual was invaluable in doing the
research for this program, and contains the entire BIOS code for
the AT, if you get the right one. You should try to get a copy of
it for your BIOS if you intend to make extensive changes to your
BIOS.

Special note for monochrome users: starting the program with
"BIOSUTIL MONO" will disable the annoying color effects on
monochrome monitors.

Biosutil V1.1
InfoMatrix Bios utilities for the AT BIOS.
Brad Gibson Copyright (C) 1990 by Secret Software
A division of InfoMatrix
InfoMatrix
1515 Hogansville Rd #83
Lagrange, GA 30240
InfoMatrix BBS:404-845-1714