3 ms·

This is really interesting. Any recommendations for further reading on EPIC and related technologies?

• FullyFunctional 4y ago
  In practice EPIC = IA-64 and Itanium is the only implementation, but IA-64 is probably the easier thing to search for. The only book I have is “IA-64 and Elementary Functions: Speed and Precision”. EPIC’s problem is shared with VLIW of which EPIC can be understood as a refinement. VLIW excels in a deterministic world where the compiler can predict latencies and produce a good schedule, but falls apart in face of loads with highly variable latencies (an in-order implementation has no option but to stall when load data doesn’t arrive on time). EPIC patches this a bit by allowing software prefetching and SW exposed speculation, but it comes at a significant code bloat and it can cover only a small fraction of what dynamic scheduling can cover. At Transmeta, our VLIW engine did this too (with some obvious advantages over IA-64) and we suffered from similar problems.
  • klelatti 4y ago
    Thanks!
    • FullyFunctional 4y ago
      It such a fascinating topic and the story is far from over. VLIW (maybe not EPIC though) has tremendous power efficiency so sometimes it’s the right trade-off (say, if you can cover latencies by switching to another hyper-thread). Micro-architecture is still a hot topic and everything is a trade-off. Next I’ll start talking about super scalar OoO stack machines …
      • fanf2 4y ago
        Were there any superscalar stack machines other than the inmos T9000 transputer? (It’s a bit of a cheat, though, because the transputer has a very limited stack, and the T9 worked more like a register machine, treating the very short local addressing mode as a register number)