exxos's Atari, Amiga & retro forum

There is a new 680x0 accelerator has just been announced called the PhantomX that *should* support Atari ST.

Like PiSTorm it is based on a Raspberry Pi running a 680x0 emulator but unlike PiSTorm it supports all the 680x0 I/O required by the Atari that were not used by Amiga (e.g. FC0-3 and BR/BGACK etc.)

http://retropc.net/gimons/phantomx/index.html

It's not open-source but looks interesting.

Hmm, interesting..

Another option, good.

alexh wrote: 21 Mar 2022 09:03 There is a new 680x0 accelerator has just been announced called the PhantomX that *should* support Atari ST.

Thanks for the link Alex. Always good to find an Atari booster.

However, unless Google translate has got it badly wrong, this line:

'Phantom X was designed exclusively for X68000. Performance is improved by optimizing for the hardware structure of X68000. Therefore, it is not a general-purpose accelerator that can be used with other models.'

...doesnt sound too promising. :(

mrbombermillzy wrote: 21 Mar 2022 12:08 However, unless Google translate has got it badly wrong, this line:

'Phantom X was designed exclusively for X68000. Performance is improved by optimizing for the hardware structure of X68000. Therefore, it is not a general-purpose accelerator that can be used with other models.'

...doesnt sound too promising. :(

There are indeed two points that make or break the fitness as a drop-in replacement : 

* the Raspberry part that emulate the CPU (Xero). This is my understanding that this part may be lacking starting from the 68030 (mmu, dummy devices for not enough IO pins). It use an internal custom cache system taylored for the X68000, and attuned to the memory management of the computer, so this part may prevent or misbehave on a ST. For the 68000 I stay quite optimistic, though.

* There is a CPLD, I infer that it is used to get proper timings of signals critical to the bus arbitration and management, but this is just a wild guess. Maybe at this point too there may be problems

sporniket wrote: 21 Mar 2022 13:14

On top of that, the CPU in the majority of these models is the Hitachi HD68HC000. Is this an exact replica of the MC68000 version or are there differences or 'enhancements' (as there is with the various clones of the 6502)?

mrbombermillzy wrote: 21 Mar 2022 12:08 'Phantom X was designed exclusively for X68000. Performance is improved by optimizing for the hardware structure of X68000. Therefore, it is not a general-purpose accelerator that can be used with other models.'...doesnt sound too promising. :(

I have bugged the developer on Twitter over the last week or so since his announcement. He did make it sound hopeful but I am guessing it has probably already specialised to X68000 to the point of no return.

sporniket wrote: 21 Mar 2022 13:14 This is my understanding that this part may be lacking starting from the 68030 (mmu, dummy devices for not enough IO pins).

Pins should be irrelevant as the 680x0 MMU is implemented in FW?

sporniket wrote: 21 Mar 2022 13:14It use an internal custom cache system taylored for the X68000, and attuned to the memory management of the computer, so this part may prevent or misbehave on a ST. For the 68000 I stay quite optimistic, though.

Yeah I imagine that timing wise and SW wise the caches might work quite differently to the normal 680x0. It kind of makes sense because the 680x0 cache and the RPi's DRAM controller are probably quite different beasts.

mrbombermillzy wrote: 21 Mar 2022 13:38 On top of that, the CPU in the majority of these models is the Hitachi HD68HC000. Is this an exact replica of the MC68000 version or are there differences or 'enhancements' (as there is with the various clones of the 6502)?

You saw them in some Megadrive/Genesis consoles which normally had Motorola so I imagine the difference is so small it is negligible.

Any accelerator will not be compatible with Atari SW that requires precise instruction timing. If you're using an accelerator on an ST you've effectively abandoned compatibility in this area.