WinUAE blitter <-> bitplane DMA timing accuracy?

Photon · 24 November 2004, 16:24

Hi!

Getting nostalgic, so I'm coding an A500 demo in WinUAE. I'm worried because even though I've set 'Cycle Exact CPU and blitter timing' WinUAE doesn't really have any configuration settings for bitplane DMA stealing blitter cycles. At least I seem to recall that both the blitter and the bitplane DMA used even cycles, so that the more bitplanes you had on, the longer it took for the blitter toblit. Am I wrong?

However, this is not the case when I emulate my demo in WinUAE. Regardless of the number of bitplanes used, the blit takes the same amount of time. NOW: here's the problem: the point of programming A500 demos is the challenge of making the fullest possible use of the available raster time, without overdoing it so that the demo staggers.

How can I make sure that a demo developed in WinUAE won't stagger when it's transferred to Amiga? (I.e., how do I stop WinUAE from telling me that I have all this time available, when on a real Amiga, I don't?)

I have WinUAE 0.9.91.

Thanks for any help

Photon · 24 November 2004, 18:06

Having removed all irrelevant vblank code, I now notice a small difference between 1 and 5 bitplanes while blitting, about 20 raster lines for blitting that takes almost a whole frame, using 2 and 3 blitter channels. It still 'feels' like there was a bigger difference on the real Amiga, that's why you disabled as many bitplanes as you could.

Any thoughts?

24 November 2004, 16:24	#1
Photon Moderator Join Date: Nov 2004 Location: Eksjö / Sweden Posts: 5,652	WinUAE blitter <-> bitplane DMA timing accuracy? Hi! Getting nostalgic, so I'm coding an A500 demo in WinUAE. I'm worried because even though I've set 'Cycle Exact CPU and blitter timing' WinUAE doesn't really have any configuration settings for bitplane DMA stealing blitter cycles. At least I seem to recall that both the blitter and the bitplane DMA used even cycles, so that the more bitplanes you had on, the longer it took for the blitter toblit. Am I wrong? However, this is not the case when I emulate my demo in WinUAE. Regardless of the number of bitplanes used, the blit takes the same amount of time. NOW: here's the problem: the point of programming A500 demos is the challenge of making the fullest possible use of the available raster time, without overdoing it so that the demo staggers. How can I make sure that a demo developed in WinUAE won't stagger when it's transferred to Amiga? (I.e., how do I stop WinUAE from telling me that I have all this time available, when on a real Amiga, I don't?) I have WinUAE 0.9.91. Thanks for any help Last edited by Paul; 24 November 2004 at 16:25. Reason: deleted a direct signature "Henrik."

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24 November 2004, 18:06	#2
Photon Moderator Join Date: Nov 2004 Location: Eksjö / Sweden Posts: 5,652	Having removed all irrelevant vblank code, I now notice a small difference between 1 and 5 bitplanes while blitting, about 20 raster lines for blitting that takes almost a whole frame, using 2 and 3 blitter channels. It still 'feels' like there was a bigger difference on the real Amiga, that's why you disabled as many bitplanes as you could. Any thoughts?

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