Category : Communication (modem) tools and utilities
Archive   : PC-VCO22.ZIP
Filename : SPATCH.TXT

The speech driver used by PC-VCO does not work as it stands for clock
speeds other than 4.77 Mhz. This problem can be corrected as follows:

Using debug, change the bytes at offset 2a1 and 2a2 hex in the file SPEECH.COM.
The values for a 4.77 Mhz clock are 08 and 08. Change the value accordingly:

Value at 2a1 Value at 2a2 Clock speed
------------ ------------ -----------

8 8 4.77 Mhz
0Dh 0Dh 8 Mhz
11h 11h 10 Mhz
14h 14h 12 Mhz

The values above are scaled proportionately to the ratio of the desired
clock speed to 4.77 MHz. For example, 12 Mhz yeilds: 12/4.77*8 => 20.125
which I've taken as 14H. Experiment will allow you to change the value
according to your particular cpu speed, as well as the ration of clock speeds.
Both bytes should contain the same value (the on/off period for one cycle).

The following example session with debug will change the values:

Enter
copy speech.com speech-8.com
debug speech-8.com

where means the enter key. Debug will display a "-" prompt. Then enter

e2a1.

Debug will display something like "xxxx:02a1 08.". The xxxx value will
vary from computer to computer. Debug should display the number 08 as
above. If this value is not 08, then you do not have the correct SPEECH.COM
(there are several floating around) and should not continue. This patch only
works for this particular version.

To change the value for an 8Mhz clock, enter

D

Similarly, enter

e2a2.
D

followed by

w

and then

q.


The result should appear similar to:

A>debug speech-8.com
-e2a1
xxxx:02a1 08.d
-e2a2
xxxx:02a2 08.d
-w
-q
A>