3 ms·
I believe PowerPC had them as well. No idea how effective they were.
by duskwuff 2y ago
I believe PowerPC had them as well. No idea how effective they were.
- seanmcdirmid 2y agoI took computer architecture in the mid-late-90s and branch hints were talked about as a thing that was being done.
- bee_rider 2y agoYeah, in my class (a couple years ago, but not decades) they were covered as something that seemed like a neat idea, but then didn’t help much for actual programs. The general theme in that class was that everything cool added more complexity than the performance benefit could justify, and got in the way of making things wider. Same for branch delays slots.
- duskwuff 2y agoBranch delay slots were just a straight-up instance of exposing an ugly quirk of the pipeline to the programmer. They became a liability in later revisions of MIPS, as it no longer arose naturally from the architecture and had to be deliberately included.
- KerrAvon 2y agoFrom distant memory: they were effective for at least some PowerPC implementations. I don't recall how much, but it was considered worthwhile in hot code for at least some machines. However, IIRC, branch prediction wasn't as advanced at that point; a modern implementation might not see the same benefits.