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Line 81: The whole memory map is implemented by RCP, as the VR4300 only talks directly to RCP. The bus between VR4300 and RCP is called [[SysAD Interface\|SysAD]]. The RCP behaves differently with different access sizes depending on the specific area of the map and the subcomponent in charge of implementing it. The SysAD bus is described at the hardware level in the ~~dedicated~~[[SysAD Interface\|SysAD page]], but to understand the effects on memory map it is sufficient to understand how data is marshalled for reads and writes. Since SysAD is a 32-bit bus, 32-bit accesses are the "native" ones, and the others are made to work around a 32-bit data exchange. * Reads: VR4300 puts the address on the bus and the size of the access (8, 16, 32, 64). The RCP typically returns a full (aligned) 32-bit word address (or two, in case of a 64-bit read), from which the VR4300 extracts the correct portion. For instance, when reading 8-bit from address 0x0000'0001, the RCP will put on the bus the 32-bit values at 0x0000'0000 - 0x0000'0003, and the VR4300 will then just isolate the requested 8 bits.

Memory map: Difference between revisions

Memory map (view source)