Z80 arithmetic: also surprisingly terrible (2018)

Re:Z80 arithmetic: also surprisingly terrible (2018) by _Codemonkeyism on Monday January 14, 2019 @04:53AM (#18901906)

You're right, though if I remember correctly the zero page was only slightly faster than memory access.

I'm als influenced a lot by my personal circumstances, as though the Z80 took generally more cycles than the 6502, as I moved from a 1mhz 6502 (C64) to a 4mhz z80 (CPC) in general the z80 felt faster.

[ Parent | on HN ]

Re:Z80 arithmetic: also surprisingly terrible (2018) by Arnt on Monday January 14, 2019 @10:05AM (#18903454)

Maybe it actually was. Code like (java) for(A a : b) a.c = false; certainly could be written very nicely on the Z80. By keeping a in IX and laying out the data structure as a struct where all of the bools are packed into one byte, the body of that loop could be just one (slow) instruction like RES 3, IX+4. But to get that speed you had to be aware of those possibilities and design the data structure. On the 6502 you'd lay out the data structure differently, playing to that CPU's strengths.

[ Parent | on HN ]

Re:Z80 arithmetic: also surprisingly terrible (2018) by _Codemonkeyism on Tuesday January 15, 2019 @03:39AM (#18909669)

Interesting, I have no idea as I was writing assembler only, no code generation (except some assembler macros ;-)

[ Parent | on HN ]