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.

>>4
In some ways MIPS did "take over the world", mostly in unbranded Chinese devices like digital picture frames, tablets, and media players. Many routers and set-top-boxes too. Not because of performance, but because it's a cheap small core that just about any ASIC designer can put in an SoC after reading e.g. the P&H book. I would bet most of the MIPS-compatible cores out there are not actually licensed from MIPS...

>>5
On the 8086/8 and the rest of the cacheless x86 (up to the '386), REP MOVS is the fastest - all it has to do is a bus cycle to read it in, and then the cycles after that are all spent in reading/writing the data to be moved. Any other way would be slower since most of the bus bandwidth would be spent on instruction fetches.

For the 486 and Pentium I found this:

http://computer-programming-forum.com/46-asm/5157e945c6bac0ef.htm

Which shows that REP MOVS does get beaten by 38% by an unrolled loop on an Am486DX4-120 and 23% by going through the FPU on a P90 (could this be the "third version" H&P mention?), but on the 33MHz 486 it's still the fastest. No sign of that 200% difference though.

Sure rep movs on a Nehalem will be pretty fast but the authors could have been using a 386 for all you know.

Leaving aside the fact that REP MOVS was fastest on the 386, the only period in which there was significant gains from avoiding it would be in the 486 ~ Pentium era, so it would be absolutely insane to be talking about this - except perhaps as a historical point - in the fourth edition of a book released in 2012.

Or maybe they just benchmarked a ridiculously tiny copy - akin to seeing how long it takes to use a car to travel 5 meters and comparing it to walking.

I'm tempted to get out the old 386, 486, and PMMX and do some real testing with the same code I used for the above...