RDRAM Interface
The RDRAM Interface (or RI) act as a controller of the RDRAM channel to which one or more RDRAM modules are daisy-chained. It converts memory accesses from the system into RDRAM protocol commands, to which RDRAM modules responds.
The memory area devoted to RDRAM Interface and RDRAM modules is divided as follow :
| Address Range | Name | Description | |
|---|---|---|---|
| 0x0000 0000 | 0x03EF FFFF | RDRAM memory | Allows to access RDRAM memory of configured module |
| 0x03F0 0000 | 0x03FF FFFF | RDRAM registers | Allows to access RDRAM register of configured module |
| 0x0470 0000 | 0x047F FFFF | RI registers | Allows to configure RDRAM Interface behavior |
Registers
RI_MODE 0x0470 0000
| ||||||||
|---|---|---|---|---|---|---|---|---|
| 31:24 | U-? | U-? | U-? | U-? | U-? | U-? | U-? | U-? |
| — | — | — | — | — | — | — | — | |
| 23:16 | U-? | U-? | U-? | U-? | U-? | U-? | U-? | U-? |
| — | — | — | — | — | — | — | — | |
| 15:8 | U-? | U-? | U-? | U-? | U-? | U-? | U-? | U-? |
| — | — | — | — | — | — | — | — | |
| 7:0 | U-? | U-? | U-? | U-? | RW-? | RW-? | RW-? | RW-? |
| Details Below | Stop_R | Stop_T | Op_Mode [1:0] | |||||
READ/WRITE:
[3] Enable/Disable controller Receive clock automatic stopping.
[2] Enable/Disable controller Transmit clock automatic stopping.
[1:0] Operating mode of RDRAM modules (not sure if it is the operating of the controller, if it makes the controller forward orders to place RDRAM modules in these states).
0: Reset. place device in known state after poweron.
1: Active. device is active and ready to receive requests. This mode consumes the most power and is not used directly.
2: Standby. device automatically transition to this state after servicing a transaction. This is the default operating mode.
NOTE: some RDRAM datasheets mention a 4th mode PowerDown, but I'm not sure it is supported in N64 configuration.
NOTE: transition between these states takes several cycles, so after setting them some delay is necessary for them to be effective.