IMGRUN - Image file runner

Purpose is to make easier running of software (mostly games) from diverse floppy image files. Most common formats for Atari ST are ST and MSA. Such images are intended for usage with emulators.

Owners of Atari machines with hard disks want to run games from hard disk, but it is not possible with most of games in current form. Wether game is in some floppy image (menu disk), wether is in Atari files, but wont start from hard disk.

This small program will allow above for many (we will see how many %-ually by time) Atari ST games - to run them from floppy image files on real Ataris, without need to write images on floppies.

Version 5 - improved memory handling - no need for hard reset when mount new
image. Program will care to place it at top of real physical RAM.

ST and MSA images can be mounted .After selecting ST image with fileselector program will load it in RAM and set CHS values by bootsector of image.
If you get there some strange values (20 sides, 0 sides and similar) you need to enter correct CHS values before clicking GO! button. With MSA images editing is not necessary in any case (they hold CHS for all weird formats).
While loading image file you will see couple of small flashes - (program moves video RAM down). For starting click 'GO! '. Machine will reset - hold down ALT key - stays for most of hard disk drivers, to avoid load of them. It is important because of data safety on hard disks and memory usage.
Now executable bootsector from floppy image will be executed if 'Boot FI' (boot from image) is checked. Because some images have there code which blocks mounting (false virus detection, destroying of RAMdisk) it is initially turned off. For most, it will be OK. Smaller part of images starts from bootsector, most has start from AUTO folder - AUTO programs execute from RAMdisk (mounted as floppy A). Load is of course much faster.
So mounted image will survive reset in most cases (depends from games started), so you can play another one from same image without mounting again. Just press alt after reset again, to prevent hard disk driver.
When want to back on hard disk usage you need to remove mounting - ALT+Right Shift+CTRL+Del will do hard reset. It will work on TOS 1.4 and above. Shortly after pressing reset button you can always do it (except few games). Or write ImgRun on floppy and click on Hard Reset button after starting prg.
It should now work with all TOS versions. But using hard disk with TOS 1.0 is not recommended.
Program installs (maps) (logical) drive B (whether it is present or not) to real drive A - may be good for saving and keeping positions. 
Min 2MB RAM is required for usual floppy images of 720-800KB. With 1MB can run only single sided floppy images.

Notes about reasons why many game will not run:
If game or it's loader uses any direct floppy access (hardware access) it will not run.  In such cases you need to write image on floppy, and run from. Most success may expect with cracked and FILED games. If you see floppy LED activity after reset or game start for longer time, no help, must write on floppy.

Setting (checking) '16MHz MSTE' has sense only for Mega STE machine. Other STs will crash after reboot if is checked. 16MHz means faster run (graphic) for games, but not all will like it.

This concept is good for single floppy games (even better for multi games on single floppy), but not for games on more floppies. In theory, it is possible too, but is complicated to code and usage, and many of such games is ready for run/installing from/on hard disks.

Send test results, comments on this mail:

pp@ppest.org 
