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Thread: π for the Altair 8080

  1. #11

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    Ok cool, I will PM you. lets get the bug communicated to the main author Ken.
    Looks like you have made some programs for use with standard Model 100. Easy to run. Will do.
    The CP/M variant can use an external LCD display which takes care of scroll, and so will be faster.
    If you want you can tell me what file in VirtualT has the change and I can submit it.
    I can also send you what I am using to operate CP/M on Virtual T. again - PM.
    Steve

  2. #12

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    Quote Originally Posted by smp View Post
    I'm working with PI-80G on my Altair 8800c.

    Yesterday, I successfully ran 100, 200 and 500 digits, and I notice that the program takes a bit longer to get started printing out the 4 digit sequences, and longer in between sequences, for more requested total digits. Then, I decided to try for the maximum 7232, as indicated by the input message. The program took quite a while to print out the first 4 digit sequence, and then slowly prints out subsequent sequences. I manually stopped the program after letting it work for over 4 hours.

    Question: If the program is running, attempting to print out the maximum number of digits allowed, does that mean that given enough time the program will successfully finish? I would hate to let the program churn away for 6 or 8 hours and then have it crash because for whatever reason it cannot actually finish.

    TIA

    smp
    Thank you very much.
    It should work for all the digits it claims. The time of calculation depends quadratic on the number of digits. Therefore if 1000 digits require 400s then 7000 digits require 19600s ≈ 5h30m.

    Quote Originally Posted by Twospruces View Post
    Ok cool, I will PM you. lets get the bug communicated to the main author Ken.
    Looks like you have made some programs for use with standard Model 100. Easy to run. Will do.
    The CP/M variant can use an external LCD display which takes care of scroll, and so will be faster.
    If you want you can tell me what file in VirtualT has the change and I can submit it.
    I can also send you what I am using to operate CP/M on Virtual T. again - PM.
    Steve
    Hope to get results soon. I have fixed file `do_instruct.h', ASHR (SRA HL) instruction code. I have changed line
    Code:
    i = L & CY;
    with
    Code:
    i = L & 1;
    .

  3. #13

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    For the development of a version for CP/M, I need to know are timer interrupts active with CP/M? Do they use RST to 0x003C?

  4. #14

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    looks like it does.. keyboard scan runs there.
    3c.JPG

  5. #15

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    So, you would make a correction to this document? It disagrees-
    arhl.JPG

  6. #16

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    Pi calculation times for TRS-80 Model 100:
    100: 3.25391
    300: 27.09375
    1000: 291.57813
    3000: pending

    Running in BASIC, 32k RAM, 80C85@ 2.4576MHz

  7. #17

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    Quote Originally Posted by Twospruces View Post
    So, you would make a correction to this document? It disagrees-
    It agrees. The lowest bit of L becomes CY after SRA HL. The buggy code uses value of CY before the shift.

  8. #18

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    Quote Originally Posted by Twospruces View Post
    Pi calculation times for TRS-80 Model 100:
    100: 3.25391
    300: 27.09375
    1000: 291.57813
    3000: pending

    Running in BASIC, 32k RAM, 80C85@ 2.4576MHz
    Thank you very much. The number for 3000 digits is very important. Did use CLR before RUN? The Tandy 100 scrolling is fantastically slow.
    You know I also gather screenshots of results. So if it is possible please make one for me. Thank you

  9. #19

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    Quote Originally Posted by vol.litwr View Post
    Thank you very much. The number for 3000 digits is very important. Did use CLR before RUN? The Tandy 100 scrolling is fantastically slow.
    You know I also gather screenshots of results. So if it is possible please make one for me. Thank you
    I did use CLS:RUN...

    Pi calculation times for TRS-80 Model 100:
    100: 3.25391
    300: 27.09375
    1000: 291.57813
    3000: 2563.17188

    Running in BASIC, 32k RAM, 80C85@ 2.4576MHz

    TRS80mod100_1.jpg
    TRS80mod100_2.jpg

  10. #20

    Default

    Quote Originally Posted by Twospruces View Post
    I did use CLS:RUN...
    Pi calculation times for TRS-80 Model 100:
    100: 3.25391
    300: 27.09375
    1000: 291.57813
    3000: 2563.17188
    Running in BASIC, 32k RAM, 80C85@ 2.4576MHz
    Thank you very much.
    I have checked screenshots - all digits are correct. This also proves that my emu correction has been right.
    The tables - https://litwr2.github.io/pi-spigot-b...benchmark.html - are updated.
    The results show that for the 8085 is about 15% faster for pi-spigot than the 8080 but the Z80 is faster than the 8085 for about 20%. Maybe this Z80 noticeable advantage caused by slow scrolling of the Tandy 100. So I have attached files `PINT.BA' and `CAPINT.CO' which don't print digits of the π, they print just timing. Please run it for 100, 1000 and 3000 digits (maybe only 100 and 1000 will be enough) - no CLS required.
    I also have some doubts about timings. The emulator is very inaccurate here. Could you check with a stopwatch the timings for 300 digits (it is better to use a version which outputs digits)?
    Meanwhile I have made a version for the Tandy 100 CP/M (pi-8085.com). I can't test it so it can crash the system. It uses a vector at 3eh for the interrupt redirection. Indeed I am waiting for results (100, 1000, 3000 digits; max number of digits; a screenshot) if it works properly. It is also worth to use a screen clear before its run. Please check also timings with a stopwatch for 100 or 300 digits: documentation says that it is possible to set the timer with different frequency...
    Attached Files Attached Files

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