none (none.delete@this.none.com) on August 14, 2012 4:44 am wrote:

> IMHO predication is not worth the trouble. With advanced
> micro architectures, you'd better implement a good branch predictor rather than
> spending time implementing predication (which cost can be high).

Oh, I don't disagree. The changes make sense, and I'm sure they have numbers to
back them up. And you wouldn't really expect the design choices made in 1983/84
for a 25K transistor machine to replace a 6502 and run the hand-coded BBC BASIC
interpreter to still be the best choice for 2015-2025 smartphones/tablets/servers.

I'm just nostalgic, because my first job in Oct 1983 was at Acorn Computer, sitting
just a couple of desks away from the ARM-1 design team (and working on crazy EDA
software which got thrown away). The quirks of the early ARM were really clever
solutions to some tricky problems. The problems are different now.

As a general point, it strikes me that after this cleanup, 64bit ARM is starting to
feel quite a lot like Alpha AXP. Makes me think they're really aiming to do some
very high-performance implementations ...