Falcon 030 software switches

All 680x0 related coding posts in this section please.

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EstTeeEfEm
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Falcon 030 software switches

Postby EstTeeEfEm » Fri Apr 01, 2016 4:51 am

On the falcon you can (apparently) read $ff8007 to show whether the system is in 8mhz from 16mhz.. now this may seem a bit n00b like but can this be written to in order to force a system to run at 8mhz instead of 16mhz? and are there any other requirements for this other than just changing one bit that I should be aware of? I DID try it but it just crashed in Hatari...

Thanks guys.. my game is running FAR too fast on the Falcon and its a bit ridiculous at 16mhz ;)

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AdamK
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Re: Falcon 030 software switches

Postby AdamK » Fri Apr 01, 2016 7:05 am

Yest, you can write there. It is used for better compatibility with ST/E software.
Atari: FireBee, Falcon030 + CT60e + SuperVidel + SvEthlana, TT, 520ST + 4MB ST RAM + 8MB TT RAM + CosmosEx + SC1435, 1040STFM + UltraSatan + SM124, 1040STE 4MB ST RAM + 8MB TT RAM + CosmosEx + NetUSBee + SM144 + SC1224, 65XE + U1MB + VBXE + SIDE2, Jaguar, Lynx II, 2 x Portfolio (HPC-006)

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shoggoth
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Re: Falcon 030 software switches

Postby shoggoth » Fri Apr 01, 2016 7:06 am

-------+-----+-----------------------------------------------------+----------
##############Falcon030 Processor Control ###########
-------+-----+-----------------------------------------------------+----------
$FF8007|byte |Falcon Bus Control BIT 5 . . 2 . 0|R/W (F030)
| |STe Bus Emulation (0 - on) ---------------' | ||
| |Blitter (0 - 8mhz, 1 - 16mhz) ------------------' ||
| |68030 (0 - 8mhz, 1 - 16mhz) ------------------------'|


It's supposed to work, just make sure you're in Supervisor mode.

I wouldn't recommend this approach to slow the game down however; better synchronize to some timer or VBL. There are bus speeders, accelerators etc, and those won't be affected by the settings in this register.
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