Stack Machines

On 21 Oct 2006 at 13:24, Ray Arachelian wrote: That's the bonehead way of doing things. For the way it's done right, take a look at the S/360 calling sequence--the called routine uses the STM instruction to save just the registers that will be used by it. I've worked with 3-address machines with 256 registers of 64 bits. If you're working with even a moderately-sized subroutine under those circumstances, the entire set of local variables will usually fit in the register file A smart compiler or programmer can even segment the variable set out into dynamic and static variables, so the smallest part of the register set is saved upon exit. The point is, that no matter how one touts the benefits of a cache as being able to substitute for a fast register file, it's a false claim. A cache can never have the information about the nature of a program's behavior that the programmer or compiler can--it's too far removed from the actual program context and must rely on history for what belongs in the cache and what doesn't. I could also make the same claim about virtual memory systems, but then I'd be viewed as too much of an anachronism because EVERYBODY knows that virtual memory is best, right? It's one of the classics in big-iron architecture and the darling of computer-science professors everywhere. Here's a description: http://en.wikipedia.org/wiki/Burroughs_B5000 But the fact is that even with attached FORTRAN coprocessors and vector boxes, not even a BSP could out-benchmark a CDC Cyber or Cray I on a pure computational load. Cheers, Chuck