chips
pcgeos
chips | pcgeos | |
---|---|---|
9 | 15 | |
918 | 635 | |
- | - | |
7.5 | 9.9 | |
about 1 month ago | 2 days ago | |
C | Assembly | |
zlib License | Apache License 2.0 |
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chips
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Zilog Z80 CPU – Modern, free and open source silicon clone
Because it's a software implementation in Verilog which is much closer to a software emulator and has nothing to do with the original Z80 "transistor structure".
For instance here's the LD A,(DE) "payload":
https://github.com/rejunity/z80-open-silicon/blob/974c7711b2...
And here's the equivalent in my software emulator:
https://github.com/floooh/chips/blob/bd1ecff58337574bb46eba5...
What's interesting though is that the Verilog implementation doesn't seem to update the internal WZ register, even though there are references to WZ in other places.
But in the end, if it looks and feels like a Z80 from the outside (e.g. the right pins are active at the right time) the internal implementation doesn't matter all that much.
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Getting into way too much detail with the Z80 netlist simulation (2021)
Author here, interesting to see this posted since it's more like a reference manual for Z80 instructions with 'unusual' timings. The followup blog post about the cycle-stepped Z80 emulator is probably more interesting:
https://floooh.github.io/2021/12/17/cycle-stepped-z80.html
One important note: at the start of the post I'm speculating about why I was seeing some minor differences to a 'real' Z80, it turned out that this speculation was wrong and instead the differences were caused by 'incomplete' netlist simulation code which worked fine for the 6502 but required some tweaks for the Z80, see the comments of this GH issue for details: https://github.com/floooh/v6502r/issues/2.
As far as I'm aware the netlist simulation now behaves correctly like a Zilog Z80 (but note that reverse engineered Z80 clones like the East German U880 are known to have slightly different undocumented behaviour), and the Z80 emulator in https://github.com/floooh/chips is tested against the netlist simulation for correct behaviour and timing.
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A world to win: WebAssembly for the rest of us
I simply don't see that there's a big enough difference between traditional garbage collection, refcounting and manual memory management. Each of those can already be implemented in pure WASM, just more or less awkwardly.
As for "just another ISA", there have been CPUs which had separate call- and data-stacks, with the call-stack living on the CPU and not accessible as regular data. In that sense WASM isn't much different then those esoteric CPUs.
And even though WASM might not allow free jumps, I yet have to see a noticeable performance difference between WASM and native for this type of "worst case code":
https://github.com/floooh/chips/blob/f5b6684ff6e899429544b21...
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Appler: Apple ][ emulator for IBM PC, written in 8088 assembly
Oh my, the 6502 emulation [1] has fewer lines of assembly code than my (code-generated) implementation has lines of C code [2] :D
Very nice use of a macro assembler though [3], makes the code feel very high level.
To my defense, the generated code has a lot of redundancies (such as assert(false) which were meant to catch any 'stray cycles' but which are removed in release mode.
[1] https://github.com/zajo/appler/blob/develop/src/65C02.ASM
[2] https://github.com/floooh/chips/blob/master/chips/m6502.h
[3] https://github.com/zajo/appler/blob/52aaa0f768cdf303438cd2c7...
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Ask HN: What's the best source code you've read?
I don't know if it's the best code I've ever read but this emulation library [0] of 8 bits computers is pretty well written, documented and designed: https://github.com/floooh/chips.
It's a good way to document old hardware with emulation code.
- A new cycle-stepped Z80 emulator
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Tiny Emulators
Looks like here's the source code of the emulators:
8-bit chip and system emulators in standalone C headers - https://github.com/floooh/chips
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Emulating a Parallel Memory chip at the circuit level:
There's a project on GitHub of similar nature -- it has include-able .h files emulating 8-bit computer chips on the pin level, and bus state is also held in a 64-bit value: https://github.com/floooh/chips/blob/master/chips/m6502.h
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Yet Another Eater Sap1 Is Finished
I wrote also a library of components for some complex chips (like 6502 simulation using https://github.com/floooh/chips)
pcgeos
- PC GEOS: the multitasking DOS-based GUI OS that evolved from a C64 desktop
- What OS's run over DOS other then Windows?
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Had this NOKIA-9000 communicator laying on my shelf for a long time, and I’m still amazed how cool this device was back in the day.
Runs PC-GEOS! Which recently got open sourced, if you want to write software for it... https://github.com/bluewaysw/pcgeos
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Can anyone suggest any fun to mess around with software that I can find on archive.org? I'm looking for things from old businesses or just anything fun really.
luckily we have sources now ( https://github.com/bluewaysw/pcgeos ) so that makes it much more fun. it's kinda weird to read TODO from 199x :)
- Kali Linux
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MS-DOS in Hyper-V
i was a bit joking with geos but of course, if you are curious - then try it. by now even the sources are available if you want to read some cute assembly or dive in prehistoric kernel ( https://github.com/bluewaysw/pcgeos ).
- The QNX Demo Disk: a full xNix OS, with GUI and browser, on just 1 1.4MB floppy
What are some alternatives?
wasm.cljc - Spec compliant WebAssembly compiler, decompiler, and generator
Smalltalk - By the Bluebook implementation of Smalltalk-80
s7-wasm - Example of using s7 Scheme with web assembly and emscripten
ChromeLeft4kDead - Notch's Left4kDead as a Chrome App.
makaronLab - CPU simulation experiments
Overbot - Team Overbot source code from the 2005 Grand Challenge
8086tiny - 8086tiny interpreter by Adrian Cable, taken from http://www.megalith.co.uk/8086tiny/
GladiatorPits-MUD - The source code behind Richard Woolcock's Gladiator Pits.
TypeScript - TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
mikeOS - Mirror for MikeOS 4.5 - Simple and educational Operating System written by Mike Saunders
appler - Apple ][ emulator for MS-DOS, written in 8088 assembly
webtorrent - ⚡️ Streaming torrent client for the web