i learnt how cpu work on spim
nah, you only learnt how to use them ;)
Is MIPS Dead? Lawsuit, Bankruptcy, Maintainers Leaving and More
51–60 of 95 posts
Re: Is MIPS Dead? Lawsuit, Bankruptcy, Maintainers Leaving and More
#52Earlier quoted context omitted.
It’s nice until you get to its annoying and fairly irrelevant pipelining model.
The ubiquitous delay slots in MIPS are one instruction-set feature that has aged really badly. RISC-V actively got rid of it in their design because it ends up being such a hindrance to, e.g. out-of-order implementations.
It's also a hindrance to in-order implementations that have a different number of branch delay cycles (e.g. different number of pipeline stages or instructions taking a variable number of cycles) than the original implementation.
Branch delay slots were a somewhat clever solution to reduce the complexity of the original implementation, but they baked implementation details into the ISA and became problematic when the implementation details changed.
Re: Is MIPS Dead? Lawsuit, Bankruptcy, Maintainers Leaving and More
#53Earlier quoted context omitted.
The ubiquitous delay slots in MIPS are one instruction-set feature that has aged really badly. RISC-V actively got rid of it in their design because it ends up being such a hindrance to, e.g. out-of-order implementations.
It's also a hindrance to in-order implementations that have a different number of branch delay cycles (e.g. different number of pipeline stages or instructions taking a variable number of cycles) than the original implementation. Branch delay slots were a somewhat clever solution to reduce the complexity of the original implementation, but they baked implementation details into the ISA and became problematic when the…
> they baked implementation details into the ISA and became problematic when the implementation details changed.
Same reason why stuff like VLIW has failed to catch on. These things are so dependent on specific hardware implementation details that one can hardly call them general-purpose ISA's anymore.
Re: Is MIPS Dead? Lawsuit, Bankruptcy, Maintainers Leaving and More
#54Earlier quoted context omitted.
Licensing?
My experience is that MIPS and ARM licensing are equally bad. As an anecdote, I have personally switched a MIPS core to an ARM core in an SoC revision specifically because ARM gave us better licensing terms than MIPS. It was a pain because MIPS big endian and ARM big endian are not directly compatible with each other.
Maybe it has changed, or maybe it depends on what level of IP you're licensing. The company I worked at in 2006-2009 had gone with MIPS because they were incorporating that with all sorts of other logic (from third parties plus custom) and the cost for that type of license from Arm would have bankrupted them instantly.
Re: Is MIPS Dead? Lawsuit, Bankruptcy, Maintainers Leaving and More
#55https://en.wikipedia.org/wiki/Loongson
Relevantly, Richard Stallman used to use a Lemote YeeLoong (notebook with a Loongson MIPS CPU) before he switched to a librebooted ThinkPad T400.
Re: Is MIPS Dead? Lawsuit, Bankruptcy, Maintainers Leaving and More
#56I don't think MIPS is going to completely disappear as long as Linux works on it. Someone somewhere in some country will keep making them as long as the licensing situation is more favorable for whatever use than ARM or x86. If the owning company is going bankrupt that means making MIPS CPUs will be cheaper than ARM or x86.
Hardly. It means the IP will be sold off to someone else, who might just make it more expensive to milk some profit from the deal while pushing customers to their own platform.
[deleted]
Re: Is MIPS Dead? Lawsuit, Bankruptcy, Maintainers Leaving and More
#57It's already been bought+sold a few times.
(Stanford)
MIPS Computer Systems
SGI
Spun off, IPO
Imagination
Tailwood
Wave
Re: Is MIPS Dead? Lawsuit, Bankruptcy, Maintainers Leaving and More
#58Please help me remove some of my ignorance: ARM = RISC? Intel = CISC? ? = MIPS? What else is out there in large amounts?
MIPS is sort of the original RISC, since one of the two originators of the RISC concept (Hennessy) was a founder of MIPS Computer Systems in 1984. POWER is also RISC, but basically doesn't have any traction beyond IBM itself. SPARC lives on only in radiation-hardened form for the European space agency. Various others never even achieved that level of commercial significance. So it's basically "less RISC than it used…
> SPARC lives on only in radiation-hardened form for the European space agency.
Worth noting that POWER similarly lives on in radiation-hardened form for NASA; the RAD750 (and its predecessor, the RAD3000) both have a long history of interplanetary use.
MIPS also sees some use here, too; for example, the MIPS-based Mongoose-V is what New Horizons uses, and the KOMDIV-32 ostensibly is designed for Russian spacecraft use (but I don't know of any specific examples).
Re: Is MIPS Dead? Lawsuit, Bankruptcy, Maintainers Leaving and More
#59I don't think MIPS is going to completely disappear as long as Linux works on it. Someone somewhere in some country will keep making them as long as the licensing situation is more favorable for whatever use than ARM or x86. If the owning company is going bankrupt that means making MIPS CPUs will be cheaper than ARM or x86.
I was under the impression what MIPS was open sourced, in which case "owner" company should be irrelevant?
Re: Is MIPS Dead? Lawsuit, Bankruptcy, Maintainers Leaving and More
#60Earlier quoted context omitted.
I assume that all modern CPUs are CISC-ish opcodes running in microcode on a RISC-ish core, and it’s been a few decades since those were useful labels.
There's nothing much that's CISC-like about ARM, MIPS or RISC-V. Even many μC architectures are closer to "RISC" than "CISC", though there's at least some room for exceptions there.
> There's nothing much that's CISC-like about ARM,
I struggle to think that ARM can really be called reduced-instruction after neon or so.