ao486_MiSTer
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| ao486_MiSTer | VexRiscvBPluginGenerator | |
|---|---|---|
| 21 | 1 | |
| 235 | 14 | |
| 1.3% | - | |
| 5.8 | 0.0 | |
| 7 days ago | over 1 year ago | |
| Verilog | C | |
| GNU General Public License v3.0 or later | MIT License |
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ao486_MiSTer
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Reverse engineering the Intel 386 processor's register cell
How about a 486 instead? :)
https://github.com/MiSTer-devel/ao486_MiSTer
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Issues with AO486
Have you checked all the details in https://github.com/MiSTer-devel/ao486_MiSTer ?
- Ao486_MiSTer: i486 core for the MiSTer FPGA gaming system
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Recently, I came across a video on Youtube by Linus Tech Tips about the PCEm emulator that I found to be cringy and ill-informed. As a computer engineer by education let me explain few core concepts on how emulation works.
You mention "Pentium MMX CPU" a few times in your post, but fail to mention any FPGA solution that can emulate a machine of that class. MiSTer can't do that, the best it can do is a 486 (not just missing MMX, doesn't even have an FPU).
- Exact 486 CPU Performance in Smallest Form Factor
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Emulate Any ISA Card With A Raspberry Pi And An FPGA
It has already happened: https://github.com/MiSTer-devel/ao486_MiSTer
- Are there FPGA cores for SB16/ET4KW32/NE2K?
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KEYBCS2
The last processor generation it worked on is the 486, but on a Pentium or newer it always fails with a “Debugging is not allowed” message.
I guessed the reason for that correctly - prefetch queue. Mentions of CUP386 in the comments also brought back more memories of the cracking scene in the late 80s/early 90s. There's some very interesting discussion on SMC vs CPU behaviour here --- in the context of an open-source 486-level SoC core:
https://github.com/MiSTer-devel/ao486_MiSTer/issues/33
VexRiscvBPluginGenerator
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What is your take on ISA architectures for FPGAs (x86, arm, risc-v)?
I'd say beyond availability, the primary advantage for embedded use it the adaptability of the ISA. If you just need a small microcontroller, the core can be very small; if you need some specific performance point, you can use a bigger core, some extensions (or part thereof) could help, and you can always roll your own instructions in the 'custom' opcode space to reach your goals.
What are some alternatives?
dosbox-x - DOSBox-X fork of the DOSBox project
microwatt - A tiny Open POWER ISA softcore written in VHDL 2008
PCem-ROMs - This is a collection of requiered ROMs files for PCem emulator. RIP PCem 2021
vISA
elks - Embeddable Linux Kernel Subset - Linux for 8086
libi86 - Attempt to reimplement non-standard C library facilities (e.g. <conio.h>) used in MS-DOS programs, for IA-16 GCC & ACK ― mirror of https://gitlab.com/tkchia/libi86 • Ubuntu packages for cross-compilation at https://launchpad.net/%7Etkchia/+archive/ubuntu/build-ia16/ • DJGPP/MS-DOS binaries at https://github.com/tkchia/libi86/releases
NyuziProcessor - GPGPU microprocessor architecture
gcc-ia16 - Fork of Lambertsen & Jenner (& al.)'s IA-16 (Intel 16-bit x86) port of GNU compilers ― added far pointers & more • use https://github.com/tkchia/build-ia16 to build • Ubuntu binaries at https://launchpad.net/%7Etkchia/+archive/ubuntu/build-ia16/ • DJGPP/MS-DOS binaries at https://gitlab.com/tkchia/build-ia16/-/releases • mirror of https://gitlab.com/tkchia/gcc-ia16
winevdm - 16-bit Windows (Windows 1.x, 2.x, 3.0, 3.1, etc.) on 64-bit Windows
chipyard - An Agile RISC-V SoC Design Framework with in-order cores, out-of-order cores, accelerators, and more