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Comment by pascalmemories | Hacker News Reader

Around 768 bytes. The golden days of tight code and amazing minds pulling together cool code that set the framework for floating point on 'home' computers. A great reference point and piece of history.

edit: I see from the link in the comment posted by ddingus that there is also an errata with a fix for the bug in the original code. http://codebase64.org/doku.php?id=base:errata_for_rankin_s_6...

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Well, $1fee-$1d00=750 bytes of code, + the 14 zero page locations. Its really the zero page that makes the processor function at all. When I go back to 6502 assembly, it amazes me what was possible with a processor that basically had 3 independent (because they could not be combined) 8 bit registers and a 256 byte stack.

There are some C compilers (http://www.6502.org/tools/lang/) for the processor, but it quickly becomes obvious just how poorly C fits. The 6502 is basically a processor that forces one to code with a bytecode + interpreter or in native assembly.

Which brings me back to the zero page. It is is both the solution to getting anything complex done. And simultaneously the problem because there isn't a good way to allocate space there (because the zero page locations are encoded directly in the instructions).

You need to allocate zero page as you do registers - but fortunately it's large enough (compared to the complexity of 6502 programs) that you'll probably never need to deal with spilling. So what I've always done is use the assembler to allocate bytes in zero page as required. Your code will seem to eat through the space available very quickly... and then, at some point before you run out, you'll stop needing any more.

(Trying to allocate space there dynamically is certainly a fool's errand, of course.)

Yes, but it precludes easily sharing routines from different projects. I remember being frustrated a number of times because I didn't have source for something that conflicted with another library I wanted to use.

(Just to add to this, that hundred or so free bytes in the $0300 page IIRC was also a problem. Lots of utilities used it, so I remember there being a lot of conflicts there too).

I remember coding for the 6502, such an amazingly small set of opcodes.

And I remember the small amount of memory and registers. Only the free fast zero page memory could save you.

Or, self modifying code.

So true, it gave you performance and seemingly additional addressing modes--wasn't just to obfuscate or be cute.

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