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  • 6502 Emulator for CP/M

    From Nils M Holm@21:1/5 to All on Sun Mar 10 15:09:39 2024
    To offer some content in a hopefully not dead group:

    I have written a 6502 simulator for CP/M (and DOS and Unix). With
    limited (simulated) RAM, of course, and only about 3000 instructions
    per second on a 4MHz Z80, but maybe it is still useful to someone.

    Here it is: http://localhost/t3x.org/t3x/0/sim65kit.html

    --
    Nils M Holm < n m h @ t 3 x . o r g > http://t3x.org

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    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From me@21:1/5 to Nils M Holm on Mon Mar 11 00:12:40 2024
    Cool!
    Obviously the correct link is: https://t3x.org/t3x/0/sim65kit.html
    Congrats for this 25+ years work.
    iss

    On 3/10/24 17:09, Nils M Holm wrote:
    To offer some content in a hopefully not dead group:

    I have written a 6502 simulator for CP/M (and DOS and Unix). With
    limited (simulated) RAM, of course, and only about 3000 instructions
    per second on a 4MHz Z80, but maybe it is still useful to someone.

    Here it is: http://localhost/t3x.org/t3x/0/sim65kit.html


    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Nils M Holm@21:1/5 to me@net.net on Mon Mar 11 09:24:37 2024
    me <me@net.net> wrote:
    Cool!
    Obviously the correct link is: https://t3x.org/t3x/0/sim65kit.html
    Congrats for this 25+ years work.
    iss

    Thanks! And, yeah, this is the correct link. Oops!

    Did not work on it all the time, though, just picked it up again
    and again. Most recently when I got a KIM Uno:

    http://t3x.org/kimuno/case.html

    On 3/10/24 17:09, Nils M Holm wrote:
    To offer some content in a hopefully not dead group:

    I have written a 6502 simulator for CP/M (and DOS and Unix). With
    limited (simulated) RAM, of course, and only about 3000 instructions
    per second on a 4MHz Z80, but maybe it is still useful to someone.

    Here it is: http://localhost/t3x.org/t3x/0/sim65kit.html



    --
    Nils M Holm < n m h @ t 3 x . o r g > http://t3x.org

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Fred Weigel@21:1/5 to Nils M Holm on Sat Mar 16 14:54:44 2024
    Nils

    Not a dead grou!

    Speed is interesting... Without looking at your code, I'll propose a
    design. There is (almost) 1:1 correspondence in instructions.

    Consider not emulating, but translating. I'm thinking on this -- and my
    "first cut" has 1 6502 to 3 8080. As there are only 1 byte opcodes in
    6502, max 256 entry dispatch table - so, ldax d, inx d, lxi h,t, mov c,a,
    mvi b,0 dad b, dad d, mov a,m, inx h, mov h,m, mov l,a, pchl, 3
    instructions, jmp dispatch. a bit more overhead, so 20 instructions per.
    At 4Mhz, we expect around 20,000 6502 instructions per second.

    If we remove the dipatch loop (for sequences of code with no branch we
    could achieve 4 times that. Yes, dispatch dominates. But, unfortunately we
    do not have the memory to keep track of instructions counts. If I were
    doing this in an emulator this would be easy. Doing it ON the hardware
    will be tricky. Flags only need proper calculation on certain events --
    looking at them and branching. We can go "back in time" to the previous instruction if needed. Slows us down a bit (we will need to store the
    last instruction location).

    I think I am going to play with this a while -- before looking at you
    code. On the backburner.

    And I am sorry -- interesting idea. Rambling a bit.

    -Fred
    On 10 Mar 2024 15:09:39 GMT, Nils M Holm wrote:

    To offer some content in a hopefully not dead group:

    I have written a 6502 simulator for CP/M (and DOS and Unix). With
    limited (simulated) RAM, of course, and only about 3000 instructions per second on a 4MHz Z80, but maybe it is still useful to someone.

    Here it is: http://localhost/t3x.org/t3x/0/sim65kit.html

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Nils M Holm@21:1/5 to Fred Weigel on Tue Mar 19 10:24:12 2024
    Fred Weigel <fred_weigel@hotmail.com> wrote:
    Speed is interesting... Without looking at your code, I'll propose a
    design. There is (almost) 1:1 correspondence in instructions.

    This is very interesting, but the approach is completely different from
    mine. The code in SIM65KIT tries to be easy to understand rather than
    clever, let alone optimal. Over the years the programs I am writing
    have become more and more simple and obvious. Why would I make things
    more difficult than they need to be?

    Consider not emulating, but translating. I'm thinking on this -- and my "first cut" has 1 6502 to 3 8080. As there are only 1 byte opcodes in
    6502, max 256 entry dispatch table - so, ldax d, inx d, lxi h,t, mov c,a,
    mvi b,0 dad b, dad d, mov a,m, inx h, mov h,m, mov l,a, pchl, 3
    instructions, jmp dispatch. a bit more overhead, so 20 instructions per.
    At 4Mhz, we expect around 20,000 6502 instructions per second.

    If we remove the dipatch loop (for sequences of code with no branch we
    could achieve 4 times that. Yes, dispatch dominates. But, unfortunately we
    do not have the memory to keep track of instructions counts. If I were
    doing this in an emulator this would be easy. Doing it ON the hardware
    will be tricky. Flags only need proper calculation on certain events -- looking at them and branching. We can go "back in time" to the previous instruction if needed. Slows us down a bit (we will need to store the
    last instruction location).

    I think I am going to play with this a while -- before looking at you
    code. On the backburner.

    And I am sorry -- interesting idea. Rambling a bit.

    -Fred
    On 10 Mar 2024 15:09:39 GMT, Nils M Holm wrote:

    To offer some content in a hopefully not dead group:

    I have written a 6502 simulator for CP/M (and DOS and Unix). With
    limited (simulated) RAM, of course, and only about 3000 instructions per
    second on a 4MHz Z80, but maybe it is still useful to someone.

    Here it is: http://localhost/t3x.org/t3x/0/sim65kit.html


    --
    Nils M Holm < n m h @ t 3 x . o r g > http://t3x.org

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)