Using a PC as an accelerator? Had an idea last night....

[amigaksi]

>Such a design would be totally blighted by endian conversion issues. You'd probably need to use the big-endian memory access tricks they did for amithlon.

But he is suggesting some interface hardware in between to do the CPU signal translation in real-time.

>Another problem with sticking increasingly fast cpus into a classic is the extreme latency of talking to the original hardware and handling interrupts etc raised by it. Eventually, you will have offloaded so much of the original hardware to your x86 stock kit that as bloodline says you'd wonder what it was your original system was even doing.

I think he's suggesting a pin-compatible replacement of the CPU card with a PC-interface card so as long as the timing is done in hardware (since 0x86 software won't be able handle it), it will be like adding an accelerator card.  The custom chips would have to by synced at the same 7.16Mhz using hardware so it's backward compatible (and NTSC/Pal compatible) with existing software.  Software that uses fastmem and CPU accelerators for computations currently would run faster while the chipset keeps running at the same speed.  Why would you offload sound/graphics to 0x86 hardware?  You are only making a "black-box" type replacement of the CPU.

[amigaksi]

>How does this external converter know what size element is being accessed in order to do that?

>The CPU core will perform byte/word/long/quad reads and writes on its own caches but the CPU as a whole will perform cache line transfers to/from the main memory. I can't see how any interface in between can have any way of knowing what the data being transferred is in order to to do any swapping. All it will see are long bursts of fixed width accesses.

The data/address lines (including A0) must be coming outside of the processor since the I/O ports are not cached, VGA memory is not cached, and some other areas aren't cached or configurable.  In worst case if some processor is only accessing memory via cache, you can disable the cache; at least on my Toshiba laptop, it has the option for write-through so writes are not cached.

Interesting though that people have declared in this thread:
(1) not do-able in hardware,
(2) not do-able in software (me),
(3) do-able in software, and
(4) some imagining that the entire amiga is do-able in software.