INT9FIX DOCUMENTATION Published by: PC Enterprises 2400 Belmar Blvd, Wall NJ 07719 Author: P. Joseph Calabria A known incompatibility exists with the PCjr's INT 9 routine. This is the routine used by all IBM PC's to handle keyboard information. The problem occurs with a variety of software. Anytime your PCjr keyboard will not work correctly there's a good chance INT9FIX will solve the incompatibility. Note: If you are using PC-DOS 2.10, and a program "hangs" or "crashes" without warning, this could be a different problem. Notice whether the problem always seems to occur when you press (or release) a key. If yes, install the DOS 2.10 NMI patches (found on Utility Diskette #1), or for a more effective solution consider purchasing a PCE Enterprises Compatibility Cartridge or Game-Master sidecar. When the INT 9 problem shows up programs often act as though you are pressing each key twice. (You press the letter A and AA appears on the screen.) This problem also shows up in other ways. A program may act as though you never released a key, or it may respond as though you are holding down the Shift, Alt, or Ctrl key. Note: If a program acts as though you never released a "Function Key" then may be due to a bug in the INT48 routine. As of the date this document was written, we do not have a disk-based solution for this problem, although the PC Enterprises full size keyboard and keypad, as well as the Compatibility Cartridge and Game-Master, all solve this problem. Full size keyboard used with the Racore keyboard adapter do not correct this problem. To understand the incompatibility you must first know most other IBM computers came with an 83-key keyboard, and that INT 9, when run on other IBM computers gets its information (keyboard scan codes) from a port. The PCjr came with a 62-key keyboard. Even though the PCjr's keyboard has fewer keys, the computer can still generate all the keys you'll find on an 83-key keyboard. To do this, a special BIOS routine must be run before control is passed to INT 9. This routine is called INT 48. It's INT 48's job to evaluate each key that you press, then send the correct information to INT 9. For example, lets say you want to press Function key 10. The PCjr does not have an F10 key. Instead, you press the Fn key, followed by the zero key. INT 48 receives these keys, then sends the keyboard code normally associated with the F10 key to INT 9. Here's the problem (and we can't blame this one on INT 48). Even though INT 48 writes the correctly translated 83-key keyboard code to the same port as the keyboard information would be found on a other computers, INT 9 never reads the port! Instead, INT 9 assumes the scan code is still in the AL register. This is always the case when INT 9 is run immediately after INT 48, however, if an application program prevents INT 48 from passing control directly to INT 9 a problem will show up if the program changes but does not restore the AL register. Here's another good example of why PCjr users need to let their voice be heard. The fix is so simple, it's hard to believe any software publisher would ever permit any of their programs to remain incompatible with the PCjr for this reason. All an incompatible programs needs to do is restore the AL register before passing control back to INT 9! When you install the INT9FIX program it will run just before INT 9. It simply reads the "keyboard port," puts the correct value in the AL register, then passes control to INT 9. This way, if another program that you run has changed the AL register, INT 9 will still get the correct keyboard scan code. The INT9FIX utility is one of the most important PCjr utilities on our PCjr Utility Disk. The INT 9 problem seems to show up as often as all the other incompatibilities combined. PCjr users who have not added hardware to correct this problem should be sure to execute INT9FIX each time they use their PCjr. If you do have a PCE Compatibility Cartridge or Game-Master sidecar installed you do not need to run INT9FIX. For more information on the PCE Compatibility Cartridge contact: PC Enterprises "The jrProducts Group" Customer Service: 1-908-280-0025 Order and Catalog Hotline: 1-800-922-PCjr The PCjr Lives. There is a Reason! Important Notice!!! Several software manufacturers have already contacted PC Enterprises concerning how to correct compatibility problems with their software. Dynamix, for example, has provided a new INSTALL program for Dynamix titles. The new program (available on PCE UTILITY DISKETTE #2), permits PCjr's to select Tandy modes. Previously, if you used a PCjr and tried to select the Tandy Graphics or Sound mode, you would have received the "Hardware not available" message. Please continue writing to software publishers. Always tell them how much memory your PCjr has, and about all the other hardware you are using. Tell them you're not going to continue purchasing their software if they don't respond to your needs. Your effort will be well work while!