A82: Re: Game Speed

To: <assembly-82@lists.ticalc.org>
Subject: A82: Re: Game Speed
From: "Dines Justesen" <dines@resnet.gatech.edu>
Date: Sun, 15 Nov 1998 14:30:09 -0500
Delivered-To: assembly-82-outgoing@towerguard.unix.edu.sollentuna.se
Reply-To: assembly-82@lists.ticalc.org

Normally setting the interrupts to its fastest wont increase the speed of
your game, since this increses th enumber of clock cycles spend on
interrupts, but if you need faster interrupts this is definately a way to do
it.

I do not think any one has look at what happens when you change the
interrupt speed of the calc, so you can be 100% sure of what happens.
However based on the discription of the display controller, this is what I
think happens.

The display controller has two inputs which are used to control the
frequency used to update the display (FS1 and FS2). Writing to port 4 sets
these two values, there by affecting the frequency of the display
controller. One of the output of the display controller is normally used to
control the speed of other controllers (slaves), this output is connected to
the interrupt lines on the TI82. So changing the interrupt speeds will make
the display controller use a faster frequency, and give faster interrupts.

What effect the faster frequency has on the display controller is unknow,
but you will probably ba able to use it as normal.

The CrASH people once claimed that using TURBO mode will mess up your ti82,
and the only solution was to reset the calc. I have however seen no evidence
of this, and I think the problem was that they where sending data to the
controller too fast, while it was running on the high frequency.

To test how the controller works in turbo mode, try to see if you can see
any difference in how long time the busy flag is set in normal and fast
operation. Based on this you can see if you can make your graphics routines
faster, or whether they have to be slowed down.

I do not think that you should have any problems using the fastest possible
interrupt mode, so if you need it in your game use it. However before
releasing it it would probably be a good idea to do test your program on
several different calcs, to make sure that it works.

Dines
----- Original Message -----
From: Evil Sam <evil_sam@hotmail.com>
To: <assembly-82@lists.ticalc.org>
Sent: Saturday, November 14, 1998 11:54 PM
Subject: A82: Game Speed


>
>I would like to know if this has any negative side effects. I want to
>increase the speed of a game, so I put this at the beginning of the
>code:
> LD A,$00
> out (4),a
>
>  which will put the calc interrupt speed to it's fastest.
>
>Then I put this at the end:
> LD A,%00000110
> out (4),a
>
>   which will put the calc interupt speed to normal.
>
> Basically, using "TURBO" mode only within the program. I can't think of
>a reason why this would be bad. Dines? Or anyone else know? I know this
>would be really beneficial in Mega Man 82.
>
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