> limited by the need to discover instruction boundaries
Keller specifically addressed this. His view is that yes, the x86 instruction width problem is real, but it's not an important performance bottleneck because decoders are now sophisticated enough that other bottlenecks (predictors) dominate the net performance. Yes, this means more power usage and die area, but only a part of the market is sensitive to this: where other considerations dominate the cost premium of x86 can be ignored.
He also believes that "RISC-V is the future of computing," (not surprising from the CEO of a RISC-V vendor,) so it isn't as if the legacy ISAs are somehow just fine. But ISA complexity isn't the key determinant in that future. The keys are the open ISA, commoditization of designs and high software portability.
This makes sense to me. x86, despite it's inherent issues, has fought off alternatives before. But now, as per Keller, there is a Cambrian explosion of RISC-V designs appearing, and what emerges from that is going to prevail against any legacy ISA, not just x86. Ulitimately, therefore, the x86 "tax" doesn't actually matter.
Keller specifically addressed this. His view is that yes, the x86 instruction width problem is real, but it's not an important performance bottleneck because decoders are now sophisticated enough that other bottlenecks (predictors) dominate the net performance. Yes, this means more power usage and die area, but only a part of the market is sensitive to this: where other considerations dominate the cost premium of x86 can be ignored.
He also believes that "RISC-V is the future of computing," (not surprising from the CEO of a RISC-V vendor,) so it isn't as if the legacy ISAs are somehow just fine. But ISA complexity isn't the key determinant in that future. The keys are the open ISA, commoditization of designs and high software portability.
This makes sense to me. x86, despite it's inherent issues, has fought off alternatives before. But now, as per Keller, there is a Cambrian explosion of RISC-V designs appearing, and what emerges from that is going to prevail against any legacy ISA, not just x86. Ulitimately, therefore, the x86 "tax" doesn't actually matter.