Re: Apple and the Holy War

[regnirps@aol.com (Regnirps)]

pausch@saafNOSPAM.se  (Paul Schlyter) wrote:
 
>3. Use table-lookup whenever feasible.  Computations of e.g.
>trigonometric function at low precision can be greatly speeded up
>by using table lookup and perhaps linear interpolation between
>two table values.

I did a pile of 6502 enhancement tricks back when the Apple IIe first came out.
I made ROMs to do things like "instant multiply" of two bytes where the two
bytes form the address of the result in two ROMs, a MSB and LSB. So a multiply
was basically write write read read (or STA STX LDA LDX) in zero page since I
mapped the 4 addresses in ZP. What is that? 8 cycles?

I did some other lookup tricks and added an AMD9511 FP processor that also did
16 and 32 bit integer math.

The finale experiment was some logic and 16 bit registers mapped to ZP that did
most of the Forth inner unterpreter in hardware. It was useful for other things
since it included ZPage 16 pointers with autoincrement by 1 or 2 when they were
accesed through appropriate addresses. I was after every little bit of extra
speed back then especially for the Forth since it alowed pretty big programs in
small memory.

Charlie Springer