GlobalFoundries to Acquire MIPS

Put that in your delay slot and smoke it.

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

I'm surprised by how many other architectures use it.

Whoa, had no idea this existed. Wild stuff. Might be "somewhat" confusing to read assembler code like that without knowing about this particular technique..

Allow me to introduce you to register windows.

https://www.jwhitham.org/2016/02/risc-instruction-sets-i-hav...

Both register windows and the delay slot exist on SPARC processors, which you’re much more likely to run into in a data center (running open-source software).

Itanium was the really odd one — it not only used register windows but could offload some of the prior windows onto the heap. Most people would probably never notice… unless you’re trying to get a conservative scanning GC working and are stumped why values in some registers seem to not be traced…

Pour one out for Itanium. It tried to make the panacea of VLIW and branch hints work, but it didn't pan out.

From an interview with Bob Colwell:

'Anyway this chip architect guy is standing up in front of this group promising the moon and stars. And I finally put my hand up and said I just could not see how you're proposing to get to those kind of performance levels. And he said well we've got a simulation, and I thought Ah, ok. That shut me up for a little bit, but then something occurred to me and I interrupted him again. I said, wait I am sorry to derail this meeting. But how would you use a simulator if you don't have a compiler? He said, well that's true we don't have a compiler yet, so I hand assembled my simulations. I asked "How did you do thousands of line of code that way?" He said “No, I did 30 lines of code”. Flabbergasted, I said, "You're predicting the entire future of this architecture on 30 lines of hand generated code?" [chuckle], I said it just like that, I did not mean to be insulting but I was just thunderstruck. Andy Grove piped up and said "we are not here right now to reconsider the future of this effort, so let’s move on".'

https://www.sigmicro.org/media/oralhistories/colwell.pdf

Sun had some funny stories around this too. When they came up with their multi-core system, and they used code from 10-15 years earlier for traces. And then said 'well, nobody actually uses floating code' so we don't need it. Of course over those 10 years Floating point became much more common and stand. Leading to a chip that had one FPU for 8 cores, basically meaning, even minimal floating point would destroy concurrency. Arguably Sun had already lose the chip war and this was just making them fall behind further. They did market it in quite well.

And a lesser known thing that I couldn't find much information on is that Sun also worked on VLIW chip during the 90s. Apparently Bill Joy was convinced that VLIW was the future so they did a VLIW chip, and the project was lead by David Ditzel. As far as I am aware this was never released. If any Sun veterans have any idea about this, I would love to know.

As far as the single FPU that you mention, the T1 is an open-source CPU.

https://www.oracle.com/servers/technologies/opensparc-t1-pag...

The T2 is also open, and places an FPU in each core.

https://www.oracle.com/servers/technologies/opensparc-t2-pag...

When there is such complaint about closed firmware in the Raspberry Pi, and the risk of the Intel ME and other closed CPU features, I wonder why these open designs are ignored. Yes, the performance and power consumption would be poor by modern standards.