Tried searching for the answer but perhaps I didn't Google the right query.

Say you have an A500 plus with a battery installed for the clock on the motherboard, then you buy a RAM expansion with a battery backed RTC on. Which one does the system use? Do both get written to when you save the time?

I need to know... Don't know why I do but I think it's interesting.

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Amiga A1200, 3.1 ROMs, Blizzard 1230 MKIV 64MB & FPU, 4GB DoM SSD, Workbench 3.1

@A1200

It depends on how the "device" is implemented. If it is a proper "Amiga" I/O hardware, then it will be auto-configuring. Thus the MB clock and the add-on clock will be two separate devices, situated at two separate bus addresses.

The device driver will only know about one of them, the first one it comes to (it is possible, but most unlikely, that it might support more than one), so only one of the two clocks will be read/written to.

Which one it is depends on which comes first in the auto-configure chain. That is likely to be the MB clock, leaving the add-on clock unused.

On the other hand, if the add-on clock is just a non auto-configure device at a fixed bus address, it will have its own device driver supplied as add-on software (as we used to do with home-brew clocks etc in the A1000 days). In that case, there is the possibility that the add-on software would patch the built-in commands like "SetClock" to use its own device.

In either case, it is most unlikely that both clocks would be read or written to.

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cheers
tony

Hyperion Support Forum: http://forum.hyperion-entertainment.biz/index.php

@tonyw

Thanks Tony, I knew there must have been some logic when they designed it or else people would have been complaining about the clock all over the Internet. Gotta love that old HW.

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Amiga A1200, 3.1 ROMs, Blizzard 1230 MKIV 64MB & FPU, 4GB DoM SSD, Workbench 3.1

@A1200

If I recall the Commodore spec on the A500 expansion port, the RTC on the add-on card will override the motherboard RTC. The OS will only see it.

Drrelio77