W-RAM

W-RAM (work RAM) is the SNES onboard memory. 128 kB (131072 bytes) big, it's clocked at 2.68 MHz and can be accessed though addresses$7E:0000-\$7F:FFFF, as well on addresses$0000-\$1FFFthough banks$00-\$3F/$80-$BFand though ports$2180-\$2183on the address bus B. The SA-1 CPU can't access the W-RAM.

SA-1 Pack moves most of the W-RAM addresses to either I-RAM or BW-RAM to make the contents accessible and faster for the SA-1 system. Because of that, a good portion of the W-RAM is either left unused or modified for another cause which does not involve SA-1 CPU access.

Code Memory

The patch places some routines on the W-RAM for several reasons, but the most important of them is to allow that SA-1 CPU will always access the ROM memory at 10.74 MHz when the SNES CPU is idle or busy doing a process that does not need ROM access.

W-RAM Memory Map

Only modified W-RAM addresses are displayed on this document. For checking other SMW addresses, look for the SMW Central RAM map.

Bank $7E

Start	End	Description
$0000	$000F	Scratch Memory. Some codes does not use the I-RAM at all for certain reasons, such as for executing code on the memory. FuSoYa's SA-1 version of LC_LZ2 and LC_LZ3 implementation are examples of that. The reason of that is ZSNES. See Known Issues to understand why.
$0010	$0FFF	Empty. Not cleared.
$1000	$1E7F	Empty. Not cleared. Reserved by SA-1 Pack for future expansion.
$1D00	-	IRQ-as-NMI system (x------e) Bit 0 (e): When set, the V-Blank routine is moved to an IRQ and NMI is disabled. Bit 7 (x): When set, the next IRQ will be the V-Blank routine. Used internally wheneis set.
$1D01	-	Which scanline should the V-Blank run when$1D00is set.
$1D02	-	Custom IRQ handler flag. If set, all IRQs, with exception of IRQ-as-NMI handler will run on the pointer located at$1D04-\$1D06instead of running on the regular SMW IRQ handelr.
$1D03	-	Copy of the register$2224. When setting$2224, make sure to set this address as well. This address is used to restore the$2224register value after an IRQ is executed.
$1D04	$1D06	Custom IRQ handler pointer. All IRQs will jump to this pointer when$1D02is set.
$1D07	-	Reserved for future use.
$1D08	$1DFF	This is where the IRQ controller is uploaded at game reset and is responsible for controlling all S-CPU IRQs received. Calling$1D08activates the IRQ-as-NMI system on the next IRQ call, if enabled.
$1E00	$1E7F	Empty. Not cleared. Reserved by SA-1 Pack for future expansion.
$1E80	$1E8D	SA-1 Execute Pointer. When called, the routine will invoke the SA-1 CPU to run a certain code and wait until the execution is finished.
$1E8E	$1E95	The game main loop. It waits for a NMI and then resumes executing.
$1E96	$1EA6	The wait for H-Blank routine. Waits until h-blank starts. When the emulator is ZSNES, this routine is replaced with a special version.
$1EA7	$1EFF	Empty. Not cleared. Reserved by SA-1 Pack for future expansion.
$1F00	$1FFF	Reserved for the SNES CPU stack.
$2000	$C7FF	Untouched by SA-1 Pack.
$C800	$FFFF	Empty. Not cleared. Reserved by SA-1 Pack for future expansion.

Bank $7F

Start	End	Description
$0000	$9A7A	Untouched by SA-1 Pack.
$9A7B	$9C7A	Empty. Not cleared.
$9C7B	$C7FF	Untouched by SA-1 Pack.
$C800	$FFFF	Empty. Not cleared. Reserved by SA-1 Pack for future expansion.