Re: [stella] Zero-Page Memory Addressing.. (Still a newbie, but getting there.)

Subject: Re: [stella] Zero-Page Memory Addressing.. (Still a newbie, but getting there.)
From: Manuel Polik <cybergoth@xxxxxxxx>
Date: Fri, 02 Nov 2001 14:05:21 +0100
HiJoel!

>to me now... Absolute Addressing is 1 click slower 
right?

Depending on what you're doing, in most cases: yes!

>My question is about Zero-Page Addressing.   Any thing 
in zero-page is
>accessed with single bytes, that's easy.  But where is 
this Zero-Page stuff
>located??   

It is, as the name indicates the first page, i.e. the 
bytes from $00 to $FF (or from $0000 to $00FF to be more 
precise)

> Is it allready built into the Atari somewhere, instead 
of on the
>cart??   

Yup!

> What is the size of the Zero-Page I've seen variables 
> defined
> usually set in the &80 range..

The zero page is splitted in two equal parts.

The first from $00 - $7F is where the TIA registers are 
located. (Check out VCS.H to find out where is which.)

The second half is the famous 128 byte RAM. As you 
already found out, it's ranging from $80 - $FF.

So all RAM access is actually in the zeropage, which 
means there's very fast access here. (Any serious C64 
coder would sell his grandma for 128 Bytes free zeropage 
RAM, BTW :-))

>Thanks, 

HTH

> I'm sorry again if this is a total repeat.

Uhm, well... :-)

Greetings,
	Manuel

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