• Jim
  • Yokemate of Keyboards
    Yokemate of Keyboards
    Posts: 4977 from 2009/1/28
    From: Delaware, USA

    Andreas_Wolf wrote:
    > Emulation COULD provide adequate performance, IF it wasn't focused
    > on low end cpus like the 603e.

    The more complex the emulated CPU, the slower the emulation.

    Not necessarily true. Cpus that feature more advanced/powerful instructions can be emulated utilizing similar advanced instructions in the target processor. Emulation could be multi-threaded to some degree (particularly when emulating out of order cpus and cpus with speculative branching) allowing for some SMP support (even in situations where the emulated cpu is running non-SMP code).
    A really fast emulated 603e is still not going to be a match for a more complex emulated PPC cpu, even with the added overhead needed to emulate the more advanced component.
    And the limitations of the earlier component WILL negatively impact its ultimate capabilities.

    Adding more advanced features to early cpus is ALWAYS a bonus.
    To give you an example, we were initially considering added HD6309 instructions to an MC6809 FGPA project I have been working on.
    This would give us two additional 8 bit accumulators, an additional 16 bit accumulator and a new 32 bit accumulator, as well as new instructions like a divide instruction (to complement the 6809's multiplication instruction).
    That's still under consideration, but I'm also looking into simply using the libraries the FPGA itself is capable of executing.

    How does this relate to software emulation?
    Pretty directly.
    Efficiency and speed ARE affected by complexity, BUT how the software initially analyses the code it is to execute, and what options/paths it takes to accomplish the emulation are affected by both what it is running on (the capabilities of the host system) AND the capabilities of that which is to be emulated.

    To simplify, I could build one heck of a emulated 6809 system, with multiple cores, very high speed...greatly improved power over the older silicon, BUT I'd always be better off emulating a 68000 (or '020, '040, '060).
    Similarly, an emulated 603e is better than an emulated 68000.
    SO, it seems fairly obvious that a more powerful PPC WOULD lead not better emulation, not necessarily slower.

    [ Edited by Jim 17.02.2018 - 11:58 ]
    "Never attribute to malice what can more readily explained by incompetence"
  • »17.02.18 - 17:55