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joncampbell123 / dosbox-x

DOSBox-X fork of the DOSBox project
GNU General Public License v2.0
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Alpha Waves (infogrames) has VGA flickering #197

Closed ghost closed 6 years ago

ghost commented 8 years ago

See here: https://github.com/joncampbell123/dosbox-x/blob/master/NOTES/Alpha%20waves%20%28infogames%29.txt

Seems related to timing issue since vmemdelay=4000 led to no noticeable flickering under limited testing.

joncampbell123 commented 8 years ago

Ah, forgot about that one.

I think the best way to determine whether to work on the problem is to run the game on actual 386SX hardware (with the turbo switch off and on) and see if the flickering happens on real hardware.

Another change I suggest is to adjust the vmemdelay option to see if making video RAM slower helps the game avoid flickering.

joncampbell123 commented 6 years ago

Coming back to this later...

Running the game again, I notice that at cycles=10000 the time in the upper right hand corner runs way too fast.

It only runs at a normal speed if you slow it down to cycles=1230, but then that brings the framerate down.

I'm guessing that this game was written for really slow old PCs.

Also, found the source code: http://cc3d.free.fr/Alpha-Waves.zip

joncampbell123 commented 6 years ago

The remaining task here is to run it on an old 386SX and see if the flickering is just as bad

joncampbell123 commented 6 years ago

I can definitely confirm that on a Packard Bell 386SX at 20MHz, the game flickers as well.... and that the PC speaker music is hard on the ears.

I can stop the flickering if I toggle the turbo switch, at the cost of the frame rate.

sikthehedgehog commented 6 years ago

It does seem like the flickering is really that bad: https://www.youtube.com/watch?v=bF_a6qMeWP8

From description:

Produced using a 486 DOS system - not an emulator.

I know you said 386 but hopefully a 486 is close enough for this.

joncampbell123 commented 6 years ago

It seems like anything faster than a 8MHz 386 causes the game to flicker.

joncampbell123 commented 6 years ago

https://www.youtube.com/watch?v=WahsflP4mcc