exxos's Atari, Amiga & retro forum

Whilst developing PiStorm for Atari, I have noticed a couple of problems with EMUTos and AltRAM
1. if emulating a 68000 CPU, EMUTos does not recognise AltRAM (defined at 0x01000000)
2. I can assign a maximum of 32MB to AltRAM (68020, 30 and 40). Anything more, results in EMUTos reporting the AltRAM size = AltRAM + available system RAM - which then causes a Bus Error and EMUTos to abort loading.
eg. AltRAM defined as 64MB and Atari has 4MB of RAM, EMUTos reports AltRAM = 68MB

Does anyone know if these are known limitations?

dad664npc wrote: 02 Aug 2023 11:31 1. if emulating a 68000 CPU, EMUTos does not recognise AltRAM (defined at 0x01000000)

68000 is 24bit address bus so is limited to 16Mb address space.

Does your EmuTOS build have the correct MMU flags? Have you tried a custom build?

custom build

Just a long shot idea - I'm no expert on the matter :)

I can never successfully build on that website - can you?
/home/www/usr/bin/../lib64/gcc/m68k-atari-mint/4.6.4/cc1: error while loading shared libraries: libmpfr.so.4: cannot open shared object file: No such file or directory

Looks like someone didn't set their LD_LIBRARY_PATH. :-)

maybe invoke @czietz the expert on EmuTOS :)

DaveC wrote: 02 Aug 2023 12:11

dad664npc wrote: 02 Aug 2023 11:31 1. if emulating a 68000 CPU, EMUTos does not recognise AltRAM (defined at 0x01000000)

68000 is 24bit address bus so is limited to 16Mb address space.

That was a physical hardware limitation of the 68000 chip. I don't think emulated 68000 need to have that limitation. But you'd need to check the coding of the emulator.

dad664npc wrote: 02 Aug 2023 13:21 I can never successfully build on that website - can you?
/home/www/usr/bin/../lib64/gcc/m68k-atari-mint/4.6.4/cc1: error while loading shared libraries: libmpfr.so.4: cannot open shared object file: No such file or directory

never tried :lol:

Just did - same error

dad664npc wrote: 02 Aug 2023 13:21 I can never successfully build on that website - can you?
/home/www/usr/bin/../lib64/gcc/m68k-atari-mint/4.6.4/cc1: error while loading shared libraries: libmpfr.so.4: cannot open shared object file: No such file or directory

Maybe you can copy and paste the 'make' command (i.e. the comp. flags) to your own local build

As far as the TT-RAM question is concerned, I can confirm (personally from my TT) that EmuTOS runs fine with 256 MiB TT-RAM. Therefore, I like to rule out any general issue with EmuTOS. This must be a problem specific to the PiStorm; which I have no experience with.

For the "fake" 68000 with TT-RAM, you should check whether IS_BUS32 (32 bit bus) is set to 1, otherwise EmuTOS will not try to detect TT-RAM: https://github.com/emutos/emutos/blob/a ... C14-L36C31

Regarding the custom build website: This is generously provided by @thorsten.otto; he would have to look into the error message.

Feel free to continue the discussion on the EmuTOS-devel mailing list in case you have more technical questions: https://sourceforge.net/p/emutos/mailman/emutos-devel/.