3 ms·
OK, but I think a diagram or two of the architecture would help. And personally, I think the Z80 is easier to understand (no zero-page, no limited stack size,
by zabzonk 2y ago
OK, but I think a diagram or two of the architecture would help.
And personally, I think the Z80 is easier to understand (no zero-page, no limited stack size, etc.) but that is probably just me, though I did write professional 6502 and Z80 code way back when.
- dapperdrake 2y agoBest descriptions I heard of the zero page: 1. A bunch of numbered "local" variables 2. Data cache with numbered entries 3. 255 numbered registers IIRC it was mentioned here on HN, but sadly I lost the reference. EDIT: Formatting.
- Someone 2y ago> 3. 255 numbered registers 255? Isn’t that 256? There’s nothing special about address zero on 6502.
- masswerk 2y agoWell, on the 6510 address $01 is a port register and address $00 the related data direction register. Therefore, C64 folks tend to ignore these addresses. (So there are just 254 usable zeropage addresses on the 6510, while on a stock 6502 and other variants the full complement of 256 zeropage addresses is usable.)
- masswerk 2y agoI tend to think of them as slow registers, since they provide crucial functionality, as in pre-indexed and post-indexed indirect address modes. There is simply no indirect addressing on the 6502 without them. But the notion of "local variables" (as related to the speed advantage) may be useful, as well.
- userbinator 2y agoZ80 is also much easier to compile HLLs for, and IMHO has more in common with the 8086.
- o11c 2y agoNo opinion needed when they're both explicitly derived from the 8080.