Terry Bohning
11851 NW 37 Place
Sunrise, FL 33323

Compuserve [71036,1066]
original: 11/4/88


Rev. 1: 11/8/88
Corrected an error in the DEBUG source
was:
or byte ptr [0411],16 ;game port indicator is bit 4 of high byte
changed to
or byte ptr [0411],10 ;game port indicator is bit 4 of high byte
since DEBUG uses hex, not decimal.

Note that JOYFORCE.COM was OK, just the doc was wrong.



Force System Recognition of Joystick

Recently I fired up my AT clone's game port for the first time since
I purchased it and discovered that Striker, one of my favorite
public domain games, would not work with a joystick.

After quite a few hours of work, I found that the DOS
Equipment Check Call (INT 11H) was saying that there was
no game port! I examined my old XT BIOS source code and
found that the equipment flag is a word stored at 00:0410.
Bit 12 of the word signifies whether there is a game port
or not.

The BIOS sets this at power up based upon whether there is a
stick attached to the port or not. So if you boot up without
your stick attached, you don't have a game port.

Well, in my case, it didn't seem to matter whether the stick
was there at power-up or not, it just didn't work.

I keyed the program shown below in under DEBUG (minus
the comments of course) , saved it as JOYFORCE.COM
and now Striker works fine.

C>DEBUG
-a100
xor ax,ax ;equipment flag is in segment 0
mov ds,ax ;set Data Segreg to 0
;high byte of equipment flag is at 0x411
or byte ptr [0411],10 ;game port indicator is bit 4 of high byte
int 20 ;terminate program

-rcx
CX 0000
:0b
-njoyforce.com
-w
Writing 000B bytes
-q
C>
/********************* EOF *************************/