[earthbee]

A taken branch on the 6502 takes 3 cycles. A not taken branch followed by a Return From Subroutine instruction takes 2 + 6 cycles.

Looking up the conditional return instructions on the 8080 seems to show it takes 5 cycles when false and 11 when true.

So the two 6502 instructions add up to being two or three cycles faster than one 8080 conditional return.

[klodolph]

Cycle counts are super misleading. These processors were limited by the speed of RAM, and cycles per RAM access differed. Suppose you have RAM running at 1 MHz... maybe your 6502 is also clocked at 1 MHz, and your 8080 is clocked at 4 MHz. I know you're not trying to compare 6502 performance to 8080 performance in general, just that there's a fairly wide variation in how much you can accomplish in a cycle, and "how many RAM accesses can the processor make" is probably what you want to look for, since it's a bit more directly comparable across processors of that era.

[anyfoo]

I was not trying to compare the 6502 with the 8080 here, and I said "potentially" exactly because it depends on the architecture wether it works out (and, as said, 8088/8086 removed the conditional returns). On the 8080 specifically, conditional returns seem to be a little cheaper overall.

[jonsen]

It’s only fair to compare cycle numbers if you also compare cycle times.