DOS 2.5 FOR AXLON RAMDISK
Enhanced disk density plus 128K
by Patrick Dell'eraNow owners of the Axlon RAMdisk and the Atari 800 can take advantage of DOS 2.5 and its enhanced density storage. The following program will create a new RAMDISK.COM file compatible with the Axlon 128K RAMdisk, DOS 2.5 and a 1050 disk drive.
When Atari came out with the vastly improved, and fully compatible, DOS 2.5 that supported enhanced disk density plus the Atari 13OXE's RAMdisk, I found myself "on the horns of a dilemma."
I didn't want to give up my good ol' Atari 800 with its Axlon 128K RAMdisk board – even though neither of these classic products is still in production. However, I did want to be able to use enhanced density on my 1050 disk drive. Also, the 130XE's bank-selected memory is but 64K, while the Axlon board provides 128K.
What to do? Buy a new computer? Give up that extra RAM? No way! A little programming here, a few fiddled bytes there...
I set to work and altered the original RAMDISK.COM so it will allow ATARI DOS 2.5 to handle the Axlon 128K RAMdisk board. (RAMDISK.COM is a file on the original DOS 2.5 disk which, when residing on your boot disk, will create the 130XE RAMdisk).
THE PROGRAM
Listing 1 is a BASIC program that will create a binary file called RAMDISK.COM. Type it in with TYPO II and SAVE a copy before you RUN it.
Now, load Listing 1, place a disk with DOS 2.5 in drive 1, and RUN the program. When finished, the new RAMDISK.COM should reside on your disk.
RAMDISK.COM
On boot-up, DOS 2.5 will look for a file named RAMDISK.COM. If found, it will load and run it before beginning its search for an AUTORUN.SYS file.
Our Axlon RAMDISK.COM checks to find the Axlon 128K RAM board. If found, it checks to see if the board has already been formatted. If not, Axion RAMDISK.COM initializes DOS to indicate that D:8 is a RAMdisk, the RAMdisk is formatted, DUPSYS is copied to it, and finally MEM.SAV is written to it.
You now have the same capabilities of the 130XE RAMdisk with one exception: instead of 412 sectors free (499 minus what DUP.SYS and MEM.SAV use), you have 710 sectors free! Going to DOS takes only seconds because DUPSYS is loaded from RAMdisk. When you return from DOS to the cartridge, any program listing will be just as you left it, thanks to the RAMdisk MEM.SAV
WARNINGS AND CAVEATS
As with any modification, there are a few things to keep in mind:
Axlon RAMDISK.COM does change DOS 2.5 in memory. If you then write DOS to a disk, the changes will be written also. To remind you that you are using a modified DOS, the menu of DOS has been changed slightly. The top line is highlighted in inverse characters. The only problem with writing a modified DOS is that the modified version won't work on a 130XE with the original RAMDISK.COM. There are no other problems presently known.
If you find you need to create DOS on a new disk while you have Axlon RAMDISK.COM installed, simply use the copy function to copy DOS.SYS to the new disk. NOTE: You must use a different name than DOS.SYS for the destination. After the DOS.SYS file has been copied, you may then rename it on the new disk to DOS.SYS without any problems.
If you inadvertently delete D8:DUPSYS, you won't be able to go to DOS unless you first POKE 5439, ASC("1") – assembler users need to alter location $153F to $31 – and then put a disk with DUP.SYS into drive 1. Unless MEM.SAV is already on the disk, you will lose any program in memory.
Whenever you go to DOS with D8:MEM.SAV active, DOS will create another MEM.SAV file of as many as 45 sectors. If RAMdisk 8 does not have 45 sectors free, no problem. There is extra space in the Axlon board that DOS can't normally use. MEM.SAV uses this memory for any overflow. If you never call DOS, MEM.SAV will never take any sectors that DOS can address.
Should you inadvertently delete MEM.SAV, you can re-install MEM.SAV by simply saving a file to "D8:MEM.SAV". In BASIC, for example, SAVE "D8:MEM.SAV". Then you can again safely go to DOS without losing anything in memory.
With this new RAMDISK.COM, owners of the Axlon Ram Disk board and the classic Atari 800 computer need not feel left out. With 710 disk sectors free, perhaps we can even feel a little smug!
Machine language maven Patrick Dell'Era last appeared in Antic in December 1985 with the spectacular DISKIO Plus.