At 02:09 1994/08/11 -0400, Jeremiah A Blatz wrote: ....

PowerPC integer performance is rather impressive, i.e. faster than Pentium by a bit. One craveat, tho, Apple says "No!" to programming in assembly, and I doubt that IBM is all this happy about it either. My guess is that MacOS is approaching the Unix "distribute source, 'cause you're gonna have to do lots of re-compiles" type of thing. Just a guess, though. Anyway, there is one assembly interpreter out for PowerMacs, I don't know about the IBM PowerPCs, though.

The PowerPC floating point is even more impressive. The fmadd instruction can do "a <- b*c+d" every other clock or 30 per microsecond on the low end Power Mac. If we store 24 bits of a multiple precision number in successive elements of an arrary then the inner loop of a multiply is a routine such as: void m8(float * a, float * b, double * p) {p[0] = a[0]*b[0]; p[1] = a[0]*b[1] + a[1]*b[0]; p[2] = a[0]*b[2] + a[1]*b[1] + a[2]*b[0]; p[3] = a[0]*b[3] + a[1]*b[2] + a[2]*b[1] + a[3]*b[0]; p[4] = a[0]*b[4] + a[1]*b[3] + a[2]*b[2] + a[3]*b[1] + a[4]*b[0]; p[5] = a[0]*b[5] + a[1]*b[4] + a[2]*b[3] + a[3]*b[2] + a[4]*b[1] + a[5]*b[0]; .... p[13] = a[6]*b[7] + a[7]*b[6]; p[14] = a[7]*b[7];} The overhead consisting of loads and stores can largely be hidden since the 601 can issue both a floating point and fixed point instruction in a single clock. 1000 bit numbers can thus be multiplied in (1000/24)^2 (1/30,000,000MHz) = 59 microseconds. The outer loop is also significant but I would expect that it can be done in under 100 microseconds. Modular exponentiation of 1000 bit numbers should take about 2*(1000/24)^3 (1/30,000,000MHz) = 2.5 ms without outer loop overhead. The MPW compiler from Apple doesn't compile this code well and I may have to write it in Assembler. The documentation that comes with MPW does not discourage assembler and MPW (from Apple) includes a great assembler! In another context I wrote some C code that compiles some optimized 601 machine code (to move pixels fast) and executes it. You don't need no stinking assembler.