How much RAM?

Mr ho · Groupie Joined: 18 Apr 2002 Posts: 298 Location: Sweden

It's commonly known that the c64 has 64kb worth of RAM.
How much of those 64kb is available when coding in asm? it's like 38kb or sumfin when coding in basic.. and if I'm not mistaking the ROM takes up 20kb of the RAM.. ehm.. ?
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puterman · Groupie Joined: 26 May 2002 Posts: 224

Basically, you can use it all.

Mr ho · Groupie Joined: 18 Apr 2002 Posts: 298 Location: Sweden

ok, thanks.
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Slator · Posted: Fri Jun 07, 2002 8:36 pm Post subject:

not to be a party-loser but you cannot use the whole 64kb :-D
as some of the very first bytes cannot be used for a programm :D
so you have everything minus at least 2 bytes :D

puterman, don't smack me at lcp please :D

puterman · Groupie Joined: 26 May 2002 Posts: 224

Slator: You're on the top spot of my smacking up list for LCP.

And you actually have more than 64kB of RAM on the C-64. In colour-RAM you've got 1024 nybbles, which means 512 extra bytes.

Mayhem · Posted: Sat Jun 08, 2002 12:55 pm Post subject:

Which the Rowland Bros used for "Mayhem in Monsterland"... they said the game takes up 65k.
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Count Zero · Newbie Joined: 25 Jun 2002 Posts: 13

Ye Ye ... wonder where the real ppl are, when this is the Scene board already ... sigh ... Smile

Actually, 65536 bytes are available for at all.
-2 for the Registers $00 and $01 aswell as
ATLEAST - 8 or - 16 bytes for the stack area, which cannot be moved
and hardly limited.

As for the colorram areas, they are not usable properly ... BUT
you can extend your coding area by using the sprite pointers
$d000-$d010 for additional coding.

The IO1 and IO2 areas can be used for code on SOME 64s, depending
on the SHIELDING and interferences your system suffers.
Most 64s will not hold the data, some do ...

So to the uppermost you would have something like
$0000 - $ffff = $10000
$10000 - $02(dataport reg) - $10 (stack) + $10 sprites + $200(IO)

This makes more than 64k actually, not taking care of the different
memory configs and the necessary management.

Still, no reason to tell a game needs 65.x Kb ... hey ... there are disks and
packing techniques ...

Learnt the lesson ? Smile

l8r
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CreaMD · Posted: Wed Jun 26, 2002 1:36 am Post subject: .

YO, WORD! Man!
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puterman · Groupie Joined: 26 May 2002 Posts: 224

As it seems we're in nitpicking mode, let me point out a few details:

d000-d010 aren't sprite pointers, but sprites coordinates, and it's not $10 bytes, but $11.

And why not use some more VIC registers anyway? For example d017, d01b, d01c and d01d are available, and even d015 if you don't care what the screen looks like. You can't use them for regular code, of course, but you could place single instructions there which you jump/branch to (rts or rti), or you could use them for data.

Count Zero · Newbie Joined: 25 Jun 2002 Posts: 13

puterman wrote:

d000-d010 aren't sprite pointers, but sprites coordinates, and it's not $10 bytes, but $11.

Agreed

))

puterman wrote:

And why not use some more VIC registers anyway? For example d017, d01b, d01c and d01d are available, and even d015 if you don't care what the screen looks like. You can't use them for regular code, of course, but you could place single instructions there which you jump/branch to (rts or rti), or you could use them for data.

You could do so, but I was guessing for regular code. Smile

Whenever you are looking for stuff where to store data just for gods
sake, you might be interested in putting it into some CIA registers with
a stopped timer probably aswell then.

the only games I have seen which really makes excessive use of the RAM
are hardly worth the hazzle though. Having no RAM left usually means, there is either no space for pal/ntsc fixing, trainers, cheats and stuff OR the original coder filles some space with junk ... Smile

Refering to single filers here ... multi filers are out of the discussion ... there you can use kinky sprite POSITION POINTER (hehe) registers for probably starting the next monster program ... Smile

l8r
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