6 ms·

Spock levels of fascinating from me. I want to learn how to compile a pdp11 emulator on my mac.

by digitalsushi 2y ago

snovymgodym 2y ago
https://opensimh.org/ https://opensimh.org/ Works great on Apple Silicon
- haunter 2y ago
  What’s the difference between an emulator and a simulator in this context?
  - bityard 2y ago
    There is LOADS of gray area, overlap, and room for one's own philosophical interpretation... But typically simulators attempt to reproduce the details of how a particular machine worked for academic or engineering purposes, while emulators are concerned mainly with only getting the desired output. (Everything else being an implementation detail.) E.g. since the MAME project considers itself living documentation of arcade hardware, it would be more properly classified as a simulator. While the goal of most other video game emulators is just to play the games.
    - deleted 2y ago
      [deleted]
    - anthk 2y ago
      Not the case at all. Tons of emulators are near 100% accurate.
      - bityard 2y ago
        Huh? I didn't mention anything about accuracy. And "accuracy" (an overloaded and ill-defined term on its own) doesn't have anything to do with the differences between simulators and emulators.
      - Imustaskforhelp 2y ago
        exactly. makes you wonder , is it all just philosophical. Calling the same thing a different name.
      - Brian_K_White 2y ago
        Irrelevant to the concept being expressed, and does not invalidate. The goals merely overlap, which is obvious. Equally obviously, if two goals are similar, then the implimentations of some way to attain those goals may equally have some overlap, maybe even a lot of overlap. And yet the goals are different, and it is useful to have words that express aspects of things that aren't apparent from merely the final object. A decorative brick and a structural brick may both be the same physical brick, yet if the goals are different then any similarity in the implimentation is just a coincidense. It would not be true to say that the definition of a decorative brick includes the materials and manufacturing steps and final physical properties of a structural brick. The definition of a decorative brick is to create a certain appearance, by any means you want, and it just so happens that maybe the simplest way to make a wall that looks like a brick wall, is to build an actual brick wall. If only they had tried to make it clear that there is overlap and the definitions are grey and fuzzy and open to personal philosophic interpretation and the one thing can often look and smell and taste almost the same as the other thing, if only they had said anything at all about that, it might have headed off such a pointless confusion...
    - Imustaskforhelp 2y ago
      I don't want to offend you , but this has made me even wonder more what the difference is. It just feels that one is emulator if its philosophy is "it just works" and simulator if "well sit down kids I am going to give you proper documentation and how it was built back in my days" but I wonder what that means for programs themselves... I wonder if simulator==emulator is more truer than what javascript true conditions allow.
      - kragen 2y ago
        It's fuzzy.
  - o11c 2y ago
    In theory, an emulator is oriented around producing a result (this may mean making acceptable compromises), whereas a simulator is oriented around inspection of state (this usually means being exact). In practice the terms are often conflated.
    - codr7 2y ago
      The difference is about as crystal clear as compiler/interpreter.
      - Imustaskforhelp 2y ago
        compiler creates a binary in elf format or other format which can be run given a shared object exists. Intepreter either writes it in bytecode and then executes the bytecode line by line ? Atleast that is what I believe the difference is , care to elaborate , is there some hidden joke of compiler vs intepreter that I don't know about ?
        dpassens 2y ago
        I assume GP meant that a lot of compilers also interpret and interpreters also compile. For compilers, constant folding is a pretty obvious optimization. Instead of compiling constant expressions, like 1+2, to code that evaluates those expressions, the compiler can already evaluate it itself and just produce the final result, in this case 3. Then, some language features require compilers to perform some interpretation, either explicitly like C++'s constexpr, or implicitly, like type checking. Likewise, interpreters can do some compilation. You already mentioned bytecode. Producing the bytecode is a form of compilation. Incidentally, you can skip the bytecode and interpret a program by, for example, walking its abstract syntax tree. Also, compilers don't necessarily create binaries that are immediately runnable. Java's compiler, for example, produces JVM bytecode, which requires a JVM to be run. And TypeScript's compiler outputs JavaScript.
        codr7 2y ago
        Thank you!
  - amszmidt 2y ago
    I think it is more about design, emulation mimics what something does. A simulator replicates what something does. It is a tiny distinction, but generally I'd say that a simulator tries to accurately replicate what happens on an electrical level as good one can do. While an emulator just does things as a black box ... input produces the expected output using whatever. You could compare it to that an accurate simulator of a 74181 tries to do it by using AND/OR/NOT/... logic, but an emulator does it using "normal code". In HDL you have a similar situation between structural, behavioral design ... structural is generally based on much more lower level logic (eg., AND/NOR/.. gates ...), and behavioral on higher logic (addition, subtraction ...). "100%" accuracy can be achieved with both methods.
thequux 2y ago
Compiling an emulator is quite easy: have a look at simh. It's very portable and should just work out of the box. Once you've got that working, try installing a 2.11BSD distribution. It's well-documented and came after a lot of the churn in early Unix. After that, I've had great fun playing with RT-11, to the point that I've actually written some small apps on it.
- colechristensen 2y ago
  From the link: > It's somewhat picky about the environment. So far, aap's PDP-11/20 emulator (https://github.com/aap/pdp11 https://github.com/aap/pdp11) is the only one capable of booting the kernel. SIMH and Ersatz-11 both hang before reaching the login prompt. This makes installation from the s1/s2 tapes difficult, as aap's emulator does not support the TC11. The intended installation process involves booting from s1 and restoring files from s2.
  - aap_ 2y ago
    good luck though. my emulator is not particularly user friendly, as in, it has no user interface. i recommend simh (although perhaps not for this thing in particular).
    - colechristensen 2y ago
      So what mechanism do you have set up to reply 4 minutes after being mentioned? :)
      - aap_ 2y ago
        Compulsively checking HN i suppose :D
        lanstin 2y ago
        Also looking at threads view first before actual news helps with that.
nonrandomstring 2y ago
Yep, this is a metal-detectorists finding religious relic moment.
boznz 2y ago
Too easy! Going to build one with NAND gates.
- wglb 2y ago
  Or you could go the way of this quite impressive project: http://fpgaretrocomputing.org/ http://fpgaretrocomputing.org/
- mycall 2y ago
  Have fun with that https://hackaday.com/2017/01/03/make-logic-gates-out-of-almost-anything/ https://hackaday.com/2017/01/03/make-logic-gates-out-of-almo...
  - ForOldHack 2y ago
    You can make logic gates out of almonds???

Spock levels of fascinating from me. I want to learn how to compile a pdp11 emulator on my mac.

snovymgodym 2y ago

https://opensimh.org/ https://opensimh.org/ Works great on Apple Silicon

haunter 2y ago
What’s the difference between an emulator and a simulator in this context?
- bityard 2y ago
  There is LOADS of gray area, overlap, and room for one's own philosophical interpretation... But typically simulators attempt to reproduce the details of how a particular machine worked for academic or engineering purposes, while emulators are concerned mainly with only getting the desired output. (Everything else being an implementation detail.) E.g. since the MAME project considers itself living documentation of arcade hardware, it would be more properly classified as a simulator. While the goal of most other video game emulators is just to play the games.
  - deleted 2y ago
    [deleted]
  - anthk 2y ago
    Not the case at all. Tons of emulators are near 100% accurate.
    - bityard 2y ago
      Huh? I didn't mention anything about accuracy. And "accuracy" (an overloaded and ill-defined term on its own) doesn't have anything to do with the differences between simulators and emulators.
    - Imustaskforhelp 2y ago
      exactly. makes you wonder , is it all just philosophical. Calling the same thing a different name.
    - Brian_K_White 2y ago
      Irrelevant to the concept being expressed, and does not invalidate. The goals merely overlap, which is obvious. Equally obviously, if two goals are similar, then the implimentations of some way to attain those goals may equally have some overlap, maybe even a lot of overlap. And yet the goals are different, and it is useful to have words that express aspects of things that aren't apparent from merely the final object. A decorative brick and a structural brick may both be the same physical brick, yet if the goals are different then any similarity in the implimentation is just a coincidense. It would not be true to say that the definition of a decorative brick includes the materials and manufacturing steps and final physical properties of a structural brick. The definition of a decorative brick is to create a certain appearance, by any means you want, and it just so happens that maybe the simplest way to make a wall that looks like a brick wall, is to build an actual brick wall. If only they had tried to make it clear that there is overlap and the definitions are grey and fuzzy and open to personal philosophic interpretation and the one thing can often look and smell and taste almost the same as the other thing, if only they had said anything at all about that, it might have headed off such a pointless confusion...
  - Imustaskforhelp 2y ago
    I don't want to offend you , but this has made me even wonder more what the difference is. It just feels that one is emulator if its philosophy is "it just works" and simulator if "well sit down kids I am going to give you proper documentation and how it was built back in my days" but I wonder what that means for programs themselves... I wonder if simulator==emulator is more truer than what javascript true conditions allow.
    - kragen 2y ago
      It's fuzzy.
- o11c 2y ago
  In theory, an emulator is oriented around producing a result (this may mean making acceptable compromises), whereas a simulator is oriented around inspection of state (this usually means being exact). In practice the terms are often conflated.
  - codr7 2y ago
    The difference is about as crystal clear as compiler/interpreter.
    - Imustaskforhelp 2y ago
      compiler creates a binary in elf format or other format which can be run given a shared object exists. Intepreter either writes it in bytecode and then executes the bytecode line by line ? Atleast that is what I believe the difference is , care to elaborate , is there some hidden joke of compiler vs intepreter that I don't know about ?
      - dpassens 2y ago
        I assume GP meant that a lot of compilers also interpret and interpreters also compile. For compilers, constant folding is a pretty obvious optimization. Instead of compiling constant expressions, like 1+2, to code that evaluates those expressions, the compiler can already evaluate it itself and just produce the final result, in this case 3. Then, some language features require compilers to perform some interpretation, either explicitly like C++'s constexpr, or implicitly, like type checking. Likewise, interpreters can do some compilation. You already mentioned bytecode. Producing the bytecode is a form of compilation. Incidentally, you can skip the bytecode and interpret a program by, for example, walking its abstract syntax tree. Also, compilers don't necessarily create binaries that are immediately runnable. Java's compiler, for example, produces JVM bytecode, which requires a JVM to be run. And TypeScript's compiler outputs JavaScript.
        codr7 2y ago
        Thank you!
- amszmidt 2y ago
  I think it is more about design, emulation mimics what something does. A simulator replicates what something does. It is a tiny distinction, but generally I'd say that a simulator tries to accurately replicate what happens on an electrical level as good one can do. While an emulator just does things as a black box ... input produces the expected output using whatever. You could compare it to that an accurate simulator of a 74181 tries to do it by using AND/OR/NOT/... logic, but an emulator does it using "normal code". In HDL you have a similar situation between structural, behavioral design ... structural is generally based on much more lower level logic (eg., AND/NOR/.. gates ...), and behavioral on higher logic (addition, subtraction ...). "100%" accuracy can be achieved with both methods.

thequux 2y ago

Compiling an emulator is quite easy: have a look at simh. It's very portable and should just work out of the box. Once you've got that working, try installing a 2.11BSD distribution. It's well-documented and came after a lot of the churn in early Unix. After that, I've had great fun playing with RT-11, to the point that I've actually written some small apps on it.

colechristensen 2y ago
From the link: > It's somewhat picky about the environment. So far, aap's PDP-11/20 emulator (https://github.com/aap/pdp11 https://github.com/aap/pdp11) is the only one capable of booting the kernel. SIMH and Ersatz-11 both hang before reaching the login prompt. This makes installation from the s1/s2 tapes difficult, as aap's emulator does not support the TC11. The intended installation process involves booting from s1 and restoring files from s2.
- aap_ 2y ago
  good luck though. my emulator is not particularly user friendly, as in, it has no user interface. i recommend simh (although perhaps not for this thing in particular).
  - colechristensen 2y ago
    So what mechanism do you have set up to reply 4 minutes after being mentioned? :)
    - aap_ 2y ago
      Compulsively checking HN i suppose :D
      - lanstin 2y ago
        Also looking at threads view first before actual news helps with that.

nonrandomstring 2y ago

Yep, this is a metal-detectorists finding religious relic moment.

boznz 2y ago

Too easy! Going to build one with NAND gates.

wglb 2y ago
Or you could go the way of this quite impressive project: http://fpgaretrocomputing.org/ http://fpgaretrocomputing.org/
mycall 2y ago
Have fun with that https://hackaday.com/2017/01/03/make-logic-gates-out-of-almost-anything/ https://hackaday.com/2017/01/03/make-logic-gates-out-of-almo...
- ForOldHack 2y ago
  You can make logic gates out of almonds???