Path: chuka.playstation.co.uk!news
From: Developer Support <dev_support@interactive.sony.com>
Newsgroups: scee.yaroze.beginners
Subject: Re: Memory address selection?
Date: Wed, 09 Jul 1997 08:56:54 +0100
Organization: PlayStation Net Yaroze (SCEE)
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wardster1@hotmail.com wrote:
> 
> Hi there...
> 
> I got the Yaroze only a few days ago, but something has got me confused.
> Why do I have to choose hexadecimal value memory addressed for any data
> files that I choose to use (seq, vab, 3d objects etc.).

The convention on PlayStation is to use hexadecimal addressing;
the PC programs that directly communicate with the PlayStation
will use them, so it's easiest to stick with them throughout
rather than converting to decimal.

> 
> Does anyone have any information regarding the choice of memory adresses,
> for example, what is the top/bottom address, do I have to allocate a
> certain amount of memory etc.
> 
> Any comments would be appreciated....
> 
> See ya.

The Yaroze memory is 2Mb of main RAM from
0x80000000 - 0x801fffff. The video RAM and sound RAM are
1Mb and 0.5Mb each respectively, and the addresses for them
are not disclosed as they are acccessed via library calls.

The Yaroze kernal and base library take up the memory
from 0x80000000 - 0x8008ffff, so Never load anything before
0x80090000; this is effectively the starting address.
The top address is 0x801fffff, but the stack grows down from that
point, so best to leave it some space; hence you can take
values like 0x801f0000 or 0x801ff000 as the top-most address.

As regards allocation, you can use whatever bits of RAM you like,
as long as you avoid conflict with data files (TIM, TMD, SEQ, VH, VB,
etc) and with program space; you can use dynamic memory allocation,
or static allocation (eg declaring global arrays) or you
can directly set where you want a buffer to be, e.g.
u_long *memoryBuffer1;		// pointer:
				// treatable as base of array
memoryBuffer1 = (u_long*) 0x80090000;
	// set the memory location of memory buffer
you can define memory buffer areas quite easily, and if you
define a bottom and top address for each, and check against
these values when getting memory, all will be fine.

Note: in the makefile of a project, specify the linker option
that forces generation of a mapfile (lots of the SCEE samples
do this). The mapfile shows you exactly where things are
and how much space various parts of your program are consuming;
very useful for spotting subtle conflicts.

Lewis