home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
ftp.whtech.com
/
ftp.whtech.com.tar
/
ftp.whtech.com
/
Geneve
/
mdos
/
geneve_manual&mdos_docs
/
horizon.txt
< prev
next >
Wrap
Text File
|
2006-10-19
|
4KB
|
116 lines
Ok, here's how to make a Horizon over 800K
bootable.
The boot eprom on the Geneve only has routines
for up to Quad density disks, so we will have to "fool"
it when reading our "High Density" ramdisk so
it can find the proper sectors where SYSTEM/SYS
is located.
Format the ramdisk with Form3meg, choose Y for
"Set disk to boot MDOS" and Y for "Load SYSTEM/
SYS from disk to ramdisk" and go ahead and load
the file on the ramdisk.
Now that SYSTEM/SYS is on the Ramdisk, you will
need to find the File Descriptor Record for it. Load up
"Disk Utilities" or some other sector editor. The sector
will begin with the filename and will probably be sector
>4 or >8. Write this sector down.
You'll also need to find the first actual data sector of
SYSTEM/SYS. This sector includes the string
"reassembling". Write this sector down also.
It will probably be >200.
Now for the thinking part. We will be editing bytes
>1C, >1D, and >1E of the sector with the FDR (either
>4 or >8, you DID write that down, did'nt you?)
We will be interested in the 6 nybbles, or digits, of these
three bytes. Let's number them 1 through 6 starting at the
left digit of byte >1C.
Here's what the Nybbles mean:
Nybbles 4, 1, and 2, in that order, are the starting sector
of the file.
Nybbles 5, 6, and 3, in that order, are the number of sectors
of actual data in the file.
So if bytes >1C, >1D, and >1E are >40, >F0, and >1F,
the FDR is telling us we have a file that starts at sector
>040 and the data in it is >1FF sectors long (for any MDOS
over version 2.50, at least). Well the length is ok, but the
Geneve will load the wrong data, because it thinks the file
starts at sector >040 instead of sector >200! You'll get a
lock-up, because the wrong data was loaded in ram where
SYSTEM/SYS is supposed to be.
So lets fix it. If we edit Bytes >1C, >1D, and >1E to be
>00, >F2, and >1F, the we are telling the eprom that the
file starts at sector >200 and is >1FF sectors of data
in length, where the eprom will find the correct data.
If you've done everything right, the Geneve will now boot
from the ramdisk! If not, you'll have to disable the ramdisk
via the on-off switch, reboot from floppy, turn the ramdisk
back on, then start over and do it correctly the next time.
It DOES work, I've been doing it for years.
For a 1.44m floppy, copy SYSTEM/SYS onto a "clean"
disk. The FDR will be at sector >4. Edit Bytes >1C, >1D,
and >1E to be >00, >F2, and >1F (again, this is for MDOS
version 2.50 and greater).
WARNING! Do not perform any file operations such as
copy, move or delete on the SYSTEM/SYS file after you
have made these changes! You can copy other files to
or from the disk, but file operations on SYSTEM/SYS will
corrupt all sorts of things on the disk, just don't do it!
The information which enabled me to come up with this
procedure can be found on pages 61 through 63 of the
HFDC manual, "File Descriptor Records".
If you don't understand the above instructions, just ask
and I'll try and address any problems you may have in this
procedure.
Tony Knerr
72070.573@compuserve.com
------------------------------
I apologize for forgetting about LOAD/SYS in my
previous instructions for making a bootable 1.44m
floppy. Here's what you need to do for that file.
Copy LOAD/SYS onto the floppy after you have
copied SYSTEM/SYS.
Make the changes to the SYSTEM/SYS FDR as
stated in my previous message.
The first six bytes of the data for LOAD/SYS are:
>0000, >06DC, >A000. You'll find these at the start
of sector >400.
The FDR for LOAD/SYS will be at sector >8.
Bytes >1C, >1D, >and >1E will need to be changed
from >00, >71, >00 to >00, >74, >00 per the information
in my previous message.
Now the floppy is bootable. Do not do any file
operations on these two files as you will not be
reading or writing to the proper sectors and you'll
also mess up the bitmap. It's ok to add or remove
other files on the disk, just don't do anything to
SYSTEM/SYS or LOAD/SYS.
Again, if you need further assistance, feel free to
contact me.
Tony Knerr
72070.573@compuserve.com