There's a few things here.exxos wrote: ↑Thu May 05, 2022 2:07 pm Just a sanity check here that TOS206 does actually run from alt-ram without any crazy-ass patching ? as I was sure that PP's program which loads TOS into alt-ram did a lot of crazy patching to get it to work ?
But in this particular case I don't think there is any point in ROM running in alt-ram. The physical ROM can be accessed at 16Mhz anyway.
* Firstly, you're still running normal ROM. Don't play with AltROM.PRG until you're happy with AltRAM.PRG. AltROM.PRG is just a cool hack.
* Next, with AltROM.PRG (which we're not using), TOS isn't running from system RAM anyway.
As far as it's concerned it's running from memory at 0xE00000, just as normal. No patching required. That we allow it to be written to as well is besides the point -- we could elect not to and it would be utterly indistingishable from an external ROM chip (like yours on the ST536).
With AltROM.PRG, it's not that the system sees 4MB ST-RAM and 8MB of AltRAM and the OS is running from a reserved block within that allocation. The system only has 4MB ST-RAM and 7MB AltRAM.
You follow?
BW
PS The next evolution of AltROM, once you're happy with AltRAM, is to load the ROM image from disc instead of from phsyical ROM. This would allow you to do away with decoding logic altogether...