3 ms·
Sort of. I did find this article when searching for evidence of whether the AGU ever assists in LEA, but I'm mostly interested in the topic because I've been w
by nkurz 6y ago
Sort of. I did find this article when searching for evidence of whether the AGU ever assists in LEA, but I'm mostly interested in the topic because I've been working on-and-off with Daniel Lemire and 'BeeOnRope' on a research paper that involves getting intimately familiar with the innards of the AGU's on recent Intel. I have no doubt that the AGU exists!
Related, you might be interested in this StackOverflow, where among other things, Peter Cordes (is he here?) and BeeOnRope conclude that the Port 7 AGU cannot be acting as assist to the 3-cycle "complex" LEA: https://stackoverflow.com/questions/50557636/what-type-of-addresses-can-the-port-7-store-agu-handle-on-recent-intel-x86 https://stackoverflow.com/questions/50557636/what-type-of-ad... (expand the comments on the answer).
- zwegner 6y agoThanks for pointing out that link (I didn't click on it when I originally read the article). Deep in the comments, there's a hint of the reason for this port 7 AGU weakness: not because of the extra gates for another adder, but due to the wiring of the scheduler/bypass network, which is presumably much simpler when port 7 only handles latency-1 instructions (at least if I'm understanding that correctly). Looking forward to that paper, too!