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split charset in rasters


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#1 tebe OFFLINE  

tebe

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Posted Sun Apr 11, 2010 11:00 AM

color yellow = charset #0
color blue = charset #1

http://atariarea.kra...=108675#p108675

Atari800Win show screen OK, but Altirra no

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Edited by tebe, Sun Apr 11, 2010 11:38 AM.


#2 Tezz OFFLINE  

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Posted Sun Apr 11, 2010 12:01 PM

Whilst working on MM with the cycle counting for mid scanline changes, I've noticed a slight difference in the amount of acceptable cycles between Awin+ and Alterra. I was planning to do some tests between them and the real hardware.

#3 phaeron OFFLINE  

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Posted Sun Apr 11, 2010 2:26 PM

color yellow = charset #0
color blue = charset #1

http://atariarea.kra...=108675#p108675

Atari800Win show screen OK, but Altirra no


Yes, it looks like you've found an emulation bug -- ANTIC needs to respond one cycle later to the CHBASE change.

In general, timing accuracy in Altirra is a bit better for GTIA than it is for ANTIC or POKEY. I've fixed some of the issues in 1.5, but haven't done a full release yet, so the DMACTL and STIMER fixes are only in 1.6 test releases:

http://www.virtualdu...-1.6-test15.zip

#4 Heaven/TQA ONLINE  

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Posted Sun Apr 11, 2010 2:30 PM

can someone post a screenshot how the demo should look like?

#5 phaeron OFFLINE  

phaeron

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Posted Sun Apr 11, 2010 5:50 PM

can someone post a screenshot how the demo should look like?


Here's a picture from my NTSC 800XL. YCMV (your colors may vary).

Adding a one-cycle delay to CHBASE seems to fix the problem:
http://www.virtualdu...-1.6-test17.zip

Attached Thumbnails

  • atari800-chbase.jpg


#6 tebe OFFLINE  

tebe

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Posted Sun Apr 18, 2010 12:33 PM

disabled "badlines" (GED+ mode without badlines)

new g2f feature, but 5-th color missed and 8 first and 4 last lines from screen

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#7 Tezz OFFLINE  

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Posted Sun Apr 18, 2010 2:33 PM

disabled "badlines" (GED+ mode without badlines)

new g2f feature, but 5-th color missed and 8 first and 4 last lines from screen

interesting, so it's a software char mode via mode E? I'll go take a look at this now.

Edited by Tezz, Sun Apr 18, 2010 2:34 PM.


#8 Rybags OFFLINE  

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Posted Sun Apr 18, 2010 4:28 PM

So this uses some sort of VScrol trick?

But, what's the use of disabling badlines? That should mean you get stuck with the same 40 characters and would need to change character set every 8 lines.

#9 tebe OFFLINE  

tebe

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Posted Mon Apr 19, 2010 12:45 AM

interesting, so it's a software char mode via mode E?


yes

#10 Rybags OFFLINE  

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Posted Mon Apr 19, 2010 1:12 AM

But, what advantage does it offer over traditional G2F techniques, or Mode E?

I can visualise a situation where you might have 3 splits so you can use characters 0-119 of 8 character sets over 24 lines, but it isn't going to give any memory savings, plus you'd be stuck with whatever attributes the initial character has (bit 7).

#11 tebe OFFLINE  

tebe

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Posted Mon Apr 19, 2010 3:12 PM

But, what advantage does it offer over traditional G2F techniques, or Mode E?


nothing special, only "we can do it" :)




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