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Old 11 May 2019, 11:27   #1
Zosite
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Join Date: Feb 2011
Location: Moonlightshadow
Posts: 23
Strange CD32 + Cycle-exact (Full) issue

I'd like to report a VERY strange issue I'm currently facing and, as usual with these kind of not-so-buggy ones, leave to our gurus to decide whether it's something to be worked on or just some expected behaviour coming from a troublemaker hack.

Using CD32 Quickstart (Cycle-exact settings) + Disposable Hero (BIN/CUE) image fails to detect the CD when also enabling "CD32 turbo CD read speed", directly entering into the classic no-CD animation.

I'd really like to try with other CD images but that's the only CD32 one I have. I've other AmigaCD games but obviously the settings are quite different (Workbench installation) and "turbo read" works with them.

Why does it matter to me? Well, because it was NOT happening before...

Regression version (last one without the issue): WinUAE 4.2.0 beta3; beta4 was the 1st one showing this and I've also tried 4.2.1 latest beta, with no luck.

Possible ways to currently fix it:

- Disable "turbo CD read" (yeah, well...)
- Disable Cycle-exact (Full)
- Leaving Cycle-exact (Full) but choosing any other CPU Frequency EXCEPT "4x (A1200)": True story! Even leaving this as "Custom" with default "14.187580" frequency it works...

I'm attaching my config with the issue but then again, it's just standard default CD32 except for the "turbo mode" and CD image selection.

And finally, a quick one out of curiosity: why 14.187580 MHz? Isn't the CD32 a 68EC020@14.28 MHz?
Attached Files
File Type: uae DHero.uae (12.7 KB, 14 views)
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Old 11 May 2019, 12:35   #2
Toni Wilen
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Join Date: Aug 2001
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Age: 44
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I guess this game has "too many" TOC entries and if they transfer too quickly, something breaks in ROM code. I changed it to only "accelerate" actual CD reads, all other transfers (toc etc) are using standard speed.

Otherwise this is "normal" behavior, even tiny timing changes can cause major side-effects when doing non-standard things.
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Old 11 May 2019, 15:38   #3
Zosite
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Thank you so much, Toni! But I'm still puzzled by the fixing by changing the CPU speed to "Custom" with exactly the same speed of 4x or even choosing 8x which also works...

BTW, sorry to insist but: what about the CD32 68EC020 real speed? Was it 14.187580, 14.28 or something else? I've even read 14.32 somewhere.
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Old 11 May 2019, 18:18   #4
Toni Wilen
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Join Date: Aug 2001
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Age: 44
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Because manually set CPU speed makes CPU clock async (separate clock crystal in real world), 1x, 2x, 4x etc.. = sync mode (CPU clock is multiple of main crystal)

Main difference is that async clocked CPU read/write access to mainboard adddress space can have extra delays if CPU needs to wait until mainboard is ready for transfer (clocks are out of sync).

Most common side-effect is slower chip ram access even if CPU is (much) faster.

PAL = 28.37516/2=14.18758MHz
NTSC = 28.63636/2=14.31818MHz
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Old 12 May 2019, 03:43   #5
Zosite
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Aaaaaand... it works with last winuae.7z! Thank you so much, Toni.

And about your quick reply to my other questions, it definitely explains a few things and, what can I say?

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