Memory map: Difference between revisions
Fix explication of writes. It's RDRAM that handles byte and short writes, not RCP.
(Fix explication of writes. It's RDRAM that handles byte and short writes, not RCP.) |
|||
| (11 intermediate revisions by 2 users not shown) | |||
Line 24:
{| class="wikitable"
!style="width: 10%"|Bus / Device
! colspan=2 | Address Range
!Mirror mask!! style="width: 15%" | Name !! Description
|-
| rowspan="3" |RDRAM
| 0x00000000 || 0x03EFFFFF
|
|-
| 0x03F00000 || 0x03F7FFFF
|
|-
| 0x03F80000 || 0x03FFFFFF
|
|-
| rowspan="
| 0x04000000 || 0x04000FFF
|0x0003E000|| [[Reality Signal Processor/Interface#DMEM and IMEM|RSP DMEM]]|| RSP Data Memory
|-
| 0x04001000 || 0x04001FFF
|0x0003E000|| [[Reality Signal Processor/Interface#DMEM and IMEM|RSP IMEM]]|| RSP Instruction Memory
|-
| 0x04040000 || 0x040BFFFF
|
▲| 0x04040000 || 0x040BFFFF || [[RSP|RSP Registers]] || RSP DMAs, status, semaphore, program counter, IMEM BIST status
|-
|0x040C0000
|0x040FFFFF
|0x00000000
|Unmapped
|This area is completely ignored by the RCP. Any access in this area will freeze the CPU as the RCP will ignore the read/write and the CPU will never receive a reply.
|-
| 0x04100000 || 0x041FFFFF
|
|-
| 0x04200000 || 0x042FFFFF
|?|| RDP Span Registers || TMEM BIST status, DP Span testing mode
|-
| 0x04300000 || 0x043FFFFF
|
|-
| 0x04400000 || 0x044FFFFF
|0x001FFFC0|| [[Video Interface]] (VI) || Video control registers
|-
| 0x04500000 || 0x045FFFFF
|0x001FFFE0|| [[Audio Interface]] (AI) || Audio DMAs, Audio DAC clock divider
|-
| 0x04600000 || 0x046FFFFF
|
|-
| 0x04700000 || 0x047FFFFF
|
|-
| 0x04800000 || 0x048FFFFF
|0x001FFFC0|| [[Serial Interface]] (SI) || SI DMAs, PIF status
|-
| 0x04900000 || 0x04FFFFFF
|
|-
| rowspan="4" |PI external bus
| 0x05000000 || 0x05FFFFFF
|?|| N64DD Registers || Contains the N64DD I/O registers.
Accesses here are forwarded to the [[PI|PI bus]], with the same address within the PI address space, using the "Domain 1" configuration set.
When not present, this is a [[Peripheral Interface#Open bus behavior|PI open bus]] area.
|-
| 0x06000000 || 0x07FFFFFF
|
Accesses here are forwarded to the [[PI|PI bus]], with the same address within the PI address space, using the "Domain 1" configuration set.
When not present, this is a [[Peripheral Interface#Open bus behavior|PI open bus]] area.
|-
| 0x08000000 || 0x0FFFFFFF
|
Accesses here are forwarded to the [[PI|PI bus]], with the same address within the PI address space, using the "Domain 2" configuration set. This is one of the few address ranges which are in Domain 2, probably because it is common to access SRAM/FlashRAM with a different (slower) protocol.
When not present, this is a [[Peripheral Interface#Open bus behavior|PI open bus]] area.
|-
| 0x10000000 || 0x1FBFFFFF
|
Accesses here are forwarded to the [[PI|PI bus]], with the same address within the PI address space, using the "Domain 1" configuration set.
When not present (eg: when booting a disk-only N64DD game without a cartridge), this is a [[Peripheral Interface#Open bus behavior|PI open bus]] area.
|-
| rowspan="3" |SI external bus
| 0x1FC00000 || 0x1FC007BF
|?|| PIF ROM ([[Initial Program Load|IPL1/2]]) || Executed on boot
|-
| 0x1FC007C0 || 0x1FC007FF
|
|-
| 0x1FC00800 || 0x1FCFFFFF
|?|| Reserved || Unknown usage
|-
| rowspan="2" |PI external bus
| 0x1FD00000 || 0x1FFFFFFF
|
No known PI device uses this range, so it will normally be a [[Peripheral Interface#Open bus behavior|PI open bus]] area.
|-
|0x20000000
|0x7FFFFFFF
|0x00000000
|Unused
|Accesses here are forwarded to the [[PI|PI bus]], with the same address within the PI address space, using the "Domain 1" configuration set.
Line 102 ⟶ 126:
|-
|
| 0x80000000 || 0xFFFFFFFF
|
|}
Line 111 ⟶ 136:
* 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 <code>0x0000'0001</code>, the RCP will put on the bus the 32-bit values at <code>0x0000'0000 - 0x0000'0003</code>, and the VR4300 will then just isolate the requested 8 bits.
* Writes: VR4300 puts the address on the bus, the size of the access, and then the 32-bit value to be written. When the access is made using 8 or 16 bits, the value on the bus is prepared to match with the aligned 32-bit address. This is the same of what happens for reads, but this time it is the VR4300
Notice that misaligned address are forbidden by MIPS architecture and they will result in an Address Exception. So all accesses that go through the memory map are always aligned to the access size (eg: aligned to 2 bytes for 16-bit reads/writes).
=== Range 0x0000'0000 - 0x03EF'FFFF (RDRAM memory) ===
The accesses in this area are handled by RCP via RI (Ram Interface). When the VR4300 reads or writes a location in this range, it gets stalled while the RI communicates with the RDRAM via the RAMBUS serial protocol. As soon as the read or write is finished, the VR4300 is released. Effectively, all reads and writes are synchronous (blocking) from the point of view of the VR4300, as you would expect when accessing a RAM. All access sizes work correctly: 8-bit, 16-bit, 32-bit, 64-bit. Support smaller access sizes is implemented the RDRAM device, which uses the lower bits of '''address''' and '''access size''' passed from RCP to generate a byte mask.
The RDRAM area is the only
▲The RDRAM area is the only ares in the memory map where the RCP supports '''cached''' accesses. This allows the VR4300 to issue the cache fills/flushes at the SysAD level to leverage the internal data and instruction cache (either via the KSEG0 directly-mapped segment, or through a TLB configured with the cache setting). Instead cache requests are ignored for all the other address ranges, and they will thus freeze the CPU requiring a hard reset.
=== Range 0x03F0'0000 - 0x03FF'FFFF (RDRAM registers) ===
| |||