Hennessy and Patterson

Ostensibly one of the most widely used books for studying computer architecture so I had a look, and... WTF? Possible future CPU designers are being fed with tripe like this?

http://i62.tinypic.com/xakqr.png

Despite all the focus on MIPS and performance, it is suspiciously missing any real benchmarks of MIPS processors.

They have an interesting definition of a "desktop computer":
http://i60.tinypic.com/4lq2j7.png

"Heineken and Pilsner" would be a better name for this book, as its authors appear to be as knowledgeable about real-world computer architecture as drunken fools.

Maybe H&P didn't completely make up everything, since I think I found the resluts they used, along with the code:

http://now.cs.berkeley.edu/Td/bcopy.html

Indeed, as I suspect, the 200% improvement is only achievable on specific combinations of P5 processors and chipsets, and completely disappeared with the P6; there's 2 486 results there too, in which REP MOVS has only a <10% loss over the others. This makes me really want to get those old machines out to see if I can reproduce these results...

Trying their code on my Nehalem, the huge 64x unrolled loop is within 1% of the non-unrolled loop (sometimes faster, sometimes slower - probably the same considering measurement noise), while going through the FPU is basically identical to using MMX (not surprisingly, they both move 8 bytes at a time.) In other words, nothing magic about their code.

Interestingly, using SSE2 non-temporal moves maintains the same speed regardless of size (not surprising since it bypasses the cache), and with huge sizes is the fastest by <10% again, but that's a bit like cheating in that the difference quickly vanishes if we need to access the data that was copied (very common situation) - the cache misses that were avoided during the copy just appear later.

>>17
It works just fine with curl.