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machines: repeat 4 MB ROM in 16 MB mapped space - #241
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Per the Hammerhead ERS the ROM region is 0xFF000000-0xFFFFFFFF. We were only mapping the ROM at the uppermost 4 MB of that (0xFFC00000). The fact that copies are returned at other addresses in that range is not explicitly stated in the ERS, but it does appear to be emprically true. It's also corroborated by the 9600 wiring diagram, which shows only enough address bits for 4MB being used for the ROM. Also does the same fix for Platinum/7200, which has the same mapping and address bits, and adds some notes about this to the documentation. Fixes SheepShaver in BeOS guests, which was using 0xFF000000 to get at the hardware ROM (see https://github.com/cebix/macemu/blob/96e512bd6376e78a2869f16dcc8a9028bce5ee72/BasiliskII/src/BeOS/SheepDriver/sheep_driver.c#L454).
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Picks up dingusdev/dingusppc#241 which fixes SheepShaver running under BeOS guests. For #237
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Per the Hammerhead ERS the ROM region is 0xFF000000-0xFFFFFFFF. We were only mapping the ROM at the uppermost 4 MB of that (0xFFC00000). The fact that copies are returned at other addresses in that range is not explicitly stated in the ERS, but it does appear to be empirically true. It's also corroborated by the 9600 wiring diagram, which shows only enough address bits for 4MB being used for the ROM.
Also does the same fix for Platinum/7200, which has the same mapping and address bits, and adds some notes about this to the documentation.
Fixes SheepShaver in BeOS guests, which was using 0xFF000000 to get at the hardware ROM.