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felix86 is a new open source Linux emulator to run x86-64 Linux programs on RISC-V processors
(www.gamingonlinux.com)
this post was submitted on 02 May 2025
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So, when I think "emulation" I usually consider it to be software emulating a hardware device (e.g. the original Gameboy, audio cards for legacy programmes that required audio cards, etc.). What they're describing in the article is what has been described to me as being an abstraction/compatibility layer. So my questions are: 1.a. Is that really what this is or is it actually an emulator? b. If the latter, what makes it an emulator rather than a compat layer? 2. In general, how much do the two concepts interact? E.g. separate concepts entirely, ends of some continuum, etc.
To me it sounds like what Java or .NET JIT does. I doubt it falls strictly into emulation 🤷♂️
Yes, JIT is used for both, but we don't call JITing of Java/.Net bytecode "emulation" because there is no hardware that natively runs bytecode that we are emulating. Unlike x86_64 asm, bytecode is designed to be JITed. But yes, JITing is the defacto strategy for efficiently emulating one piece of hardware on another.
In Java or .NET, the JIT is still going from a higher level abstraction to a lower one. You JIT from CIL (common intermediate language) or Java Bytecode down to native machine code.
When you convert from a high level language to a low level language, we call it compiling.
Here, you are translating the native machine code of one architecture to the native machine code of another (x86-64 to RISC-V).
When you run code designed for one platform on another platform, we call it emulation.
JIT means Just-in-Time which just means it happens when you “execute” the code instead of Ahead-of-Time.
In .NET, you have a JIT compiler. Here, you have a JIT emulator.
A JIT is faster than an interpreter. Modern web browsers JIT JavaScript to make it faster.