MIPS R3000

https://en.wikipedia.org/wiki/R3000

by tosh • 7 years ago

37 59 7 years ago

en.wikipedia.org

pinewurst2• 7 years ago

It's still my favorite RISC processor and the only one that I actually liked coding in assembler (SPARC wasn't fun at all).

mepian• 7 years ago

How annoying were the branch delay slots?

x0re4x• 7 years ago

You could always put NOPs into delay slots by default and replace them later with something more useful.

pinewurst2• 7 years ago

Less so than register windows :)

aap_• 7 years ago

From having read lots of disassembled MIPS code I can tell you that they become second nature very quickly.

monocasa6• 7 years ago

Alpha is bae. PowerPC is great as long as you don't look at the fever dream nightmare that is it's supervisor state.

pkaye• 7 years ago

Alpha had a weakly-ordered memory model though.

kristopolous2• 7 years ago

Want one? I've got a 600mhz sitting in the cost. Totally works. I'm in Los Angeles

segfaultbuserr• 7 years ago

Alternative history time: what if MIPS R4000 hasn't been killed by Pentium? Would we be running R10000-compatibles now?

koblas• 7 years ago

It was an interesting moment, though there was a higher chance we would have been running SPARC or POWERPC. The architecture was top notch, but the company was too focused on being "MIPS Computers" not "MIPS Technology" at the time.

snvzz5• 7 years ago

Even more fun alternative history: What if Motorola didn't end 68000 with the 68060?

68060 released earlier than the pentium, and regardless it had about twice the performance per clock. But then Motorola decided to abandon 68k to focus on PowerPC.

Going further back: What if IBM picked 68000 over the 8086 for the PC?

I'm hoping RISC-V will put an end to x86. It's about time.

0815test• 7 years ago

Even more fun alternative history: What if Motorola didn't end 68000 with the 68060?

Well, then we would all be doing our computing on Amigas, or at least on Atari Falcons. People blame C= for the downfall of the Amiga, but Motorola abandoning the 68k line was a much bigger factor, with no immediate way forward being evident at the time.

tempguy9999• 7 years ago

I thought motorola did their own RISC chips, the 88000.

protomyth3• 7 years ago

I remember there was a 68000-series with a 56000 on chip. I would love to have seen a 68000 make it into the 64-bit era with a built in DSP. I did love programming those things. I would imagine some ColdFire-style pruning of the instruction set would have happened for the 64-bit era.

monocasa6• 7 years ago

Check out the Apollo Core. FPGA soft core for an out of order 68k that they call a 68080. Even in an FPGA it's faster than any released 68k.

http://www.apollo-core.com/

pjc50• 7 years ago

I'm hoping RISC-V will put an end to x86. It's about time.

Not only is this wishful thinking and ignores the success so far of ARM, it doesn't make much sense any more - x86 is already "dead", almost all modern PCs will run amd64, with x86 as a kind of short-instruction emulation mode.

fulafel• 7 years ago

Do you mean the MIPS line vs the x86 line of processors, or the R4000 vs Pentium specifically? I don't think the R4000 was "killed" by any competitor, especially the R4400 and VR4300 versions were really successful powering many SGI machines and the Nintendo 64.

monocasa6• 7 years ago

R10k killed itself, IMO. It had so many weird bugs that sort of look like today's Spectre vulnerabilities, but were so bad normal code had problems running. Like it would speculatively write into page tables and then be unable to unwind itself.

naves2• 7 years ago

We would be all now asking ourselves: What if Pentium hasn’t been killed by MIPS R4000?

ncmncm4• 7 years ago

Nah, we would be wondering about one of the others. What if Power hadn't? What if Alpha hadn't?

No one would wonder at x86 passing, it would have seemed totally obvious and overdue. Pentium surviving was astonishing. Still is. Probably another crime to lay at Microsoft's door.

opencl2• 7 years ago

MIPS is a fun architecture (other than the delay slots that plagued early RISC ISAs) and implementing a subset of it on an FPGA is still a pretty common undergraduate university course project. I was kind of amazed just how simple it is to get a basic CPU working, though even the 1988 version was quite a lot more sophisticated than the class project version (multiple cache levels, having an MMU, probably much better branch predictor, etc).

AnaniasAnanas• 7 years ago

Why does everyone seem to hate delay slots? I understand that it makes writing assembly more annoying but most people use a compiler anyway.

alain94040• 7 years ago

It makes the hardware implementation more complicated. The delay slot was perfect for the 5-pipeline original design. Once you try to push this to out of order execution (executing more than one instruction per cycle), the delay slot just doesn't make any sense.

ajross• 7 years ago

They make writing assembly more annoying. They make writing compilers more annoying.

But the big reason is that except for the case of simple, short pipeline designs like the early MIPS parts they make designing CPUs annoying too.

The second you introduced parallel decode or a branch predictor with more than a cycle of latency these things hurt and don't help.

jawnv63• 7 years ago

in addition to the complexities they add to every layer of the stack that ajross and alain94040 brought up, they're not all that useful in practice. i seem to recall that they'd rarely be over 50% utilized and the majority of instructions in the delay slot were nops

gomijacogeo• 7 years ago

There was one nifty thing that fell out from having delay slots - you could write a threading library without having to burn a register on the ABI. When you changed context to a different thread, you'd load in all the registers for the new thread except for one which held the jump address to the new thread's IP. Then, in that jump's delay slot, you load in the thread's value for that register and, presto, zero overhead threading!

cr0sh• 7 years ago

I was kind of amazed just how simple it is to get a basic CPU working

MIPS R3000

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