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Do you have any pointers to good documentation on the Alpha memory semantics? The memory semantics are of course so lax so that the processor doesn't need to c
by KMag 9y ago
Do you have any pointers to good documentation on the Alpha memory semantics?
The memory semantics are of course so lax so that the processor doesn't need to check the computed addresses of all in-flight stores before issuing a concurrent memory operation. My understanding is that it's mostly a footgun for assembly programmers, but I'd love to see any estimates of the speed and power efficiency benefits of the lax memory semantics.
- gsmadhusudan 9y agoThis is one of the raging debates within the RISC-V group and elsewhere. Is weak memory semantics really worth it or can x86 style TSO be implemented optimally.Lot of anecdotal evidence but no conclusive experiment. As part of our work we hope to try multiple memory models in our I-class and get some definitive answers.RISC-V by the way supports ARM/PPC style weak memory model or optionally an x86 style TSO.
- bonzini 9y agoARM/PPC is fine, but Alpha took it too far in my opinion (and also didn't have a read memory barrier instruction---nowadays acquire and release memory barriers would probably be preferrable).