"7-planes" feature and more..

[StingRay]

Originally Posted by coyote

So I was not the only one that found this?!?
I must check it!

It is one of Brainwalker's best intros IMHO, then again, I liked all of his stuff. =)
He's coding mobile games these days btw. =)

Originally Posted by coyote

No.
I intentionally put 7 in bplcon0 and tested the behavior.
Here is my original announcement which was somewhat later put on the internet by a friend (Kristijan Zibreg) because at that time I didn't have the internet.
http://groups.google.co.uk/group/com...0073c7a1342b56

Nice. I just wonder what made you put $7200 in BPLCON0. I did not even think of trying something like that back in the day.

Originally Posted by coyote

StingRay,

I just watched the Brainwalker's intro but can't say that I understand...
Do you by any chance know for what exactly the 7bpl trick is used in that intro?

There is some kind of "noise layer" above the analyzer in the lower part of the screen. That's what the trick is used for (thanks to Toni for checking the intro!).
(See this thread)
Check the intro on an AGA Amiga and you can clearly see where the trick is used then.

[coyote]

Originally Posted by andreas

I know that standard-established EHB mode works on A500, so there's no point in (re)testing that.

No-one said anything about standard-established EHB mode. I thought we were talking about 7bpl mode all along.

Originally Posted by andreas

However, that special way by which EHB is (automagically) invoked e. g. in your demo (using the aforementioned software trick), ought to undergo a test IMHO.

I tested it back in 1993. In one of my previous posts you will find the link to the original text I wrote in 1994 about this.

And I believe that Toni also tested it before implementing it in WinUAE.

[coyote]

Originally Posted by StingRay

There is some kind of "noise layer" above the analyzer in the lower part of the screen. That's what the trick is used for (thanks to Toni for checking the intro!).
(See this thread)
Check the intro on an AGA Amiga and you can clearly see where the trick is used then.

So I am not the only one who found about 7bpl. Not even the first one. Sigh... Well, it was nice while it lasted...

Btw, the scroller part also must use something peculiar to a500 since it also doesn't work on aga.

[StingRay]

Originally Posted by coyote

So I am not the only one who found about 7bpl. Not even the first one. Sigh... Well, it was nice while it lasted...

I am sorry to have ruined your day. I gotta ask Brainwalker how he found this trick once I'm gonna meet him again. =)

Originally Posted by coyote

Btw, the scroller part also must use something peculiar to a500 since it also doesn't work on aga.

Probably the usual "no need to wait for the blitter" thing.

[Toni Wilen]

Originally Posted by coyote

Can't you do on aga similar to what can be done on ocs/ecs?

In other words: turn on the HAM bit but turn on only 4 bitplanes. This will initiate the HAM mode in which 4 dma channels will be used for bpldat1-4 while bpldat5 and bpldat6 will be used as a pattern. Simply fill them once and that's it.

If I remember it correctly I did something similar in B2 for the morphing globe routine. I used HAM with 5 bpls activated and filled the bpldat6 with a pattern. This way I saved some dma accesses. I used HAM to fill the horizontal lines.

I think HAM with 4 bpls will also work. Maybe HAM works even with fewer bpls, but this gives you nothing speed wise because 4 channel dma is always dedicated for screen. (Toni feel free to correct me if I am wrong...)

You remember wrong because that does not work.

Denise ignores all disabled planes. HAM5 = 6th plane is always zero, BPL6DAT is ignored. HAM4 = both BPL5DAT and BPL6DAT are ignored.

[coyote]

Originally Posted by Toni Wilen

You remember wrong because that does not work.

Denise ignores all disabled planes. HAM5 = 6th plane is always zero, BPL6DAT is ignored. HAM4 = both BPL5DAT and BPL6DAT are ignored.

Sorry...
And thank you for correcting me!

[Toni Wilen]

Originally Posted by coyote

I intentionally put 7 in bplcon0 and tested the behavior.
Here is my original announcement which was somewhat later put on the internet by a friend (Kristijan Zibreg) because at that time I didn't have the internet.
http://groups.google.co.uk/group/com...0073c7a1342b56

Copper strobe/blitter problem: time to do some logic analyzer tests soon

ADDED: I can confirm this weird "feature". COPJMP2 also does the same. (COPLC2 gets copied to BLTDPT)

[Toni Wilen]

More about COPJMP+Blitter problem..

It can be triggered very easily without multiple strobes if bitplanes are disabled. Only need to access COPJMP1 or 2 while blitter is running and copper was waiting.

Interesting notes:

D-channel only: pointer changes
C-channel only: pointer also changes
A or B channel only: blitter works as expected

(A,B, C cases checked with logic analyzer by snooping data bus)

Multiple channel combinations not yet tested.

[coyote]

Originally Posted by Toni Wilen

Multiple channel combinations not yet tested.

I see that you are thoroughly testing this bug...
Hope only that you won't decide to emulate it.

Anyway, it seems that soon WinUAE will be better than the real thing.