Changes

|-

|-

| 0

| 0

| Enable bootrom instruction overlay, maybe? This bit is only writable for core2 and core3.

| nRESET, 0 = reset. Also enable the bootrom instruction overlay.

|-

|-

| 1

| 1

| Enable bootrom data overlay. This bit is only writable for core2 and core3.

| Enable bootrom data overlay

|-

|-

| 4

| 4

| Has core booted maybe?

| Reset operation in progress

|-

|-

| 5

| 5

|}

|}

The normal ARM11 bootrom checks cpuid and hangs if cpuid >= 2. This is a problem when booting the 2 additional New3DS ARM11 MPCores. NewKernel11 solves this by using a hardware feature to overlay the bootrom with a configurable branch to a kernel function. This overlay feature was added with the New3DS.

 

The normal Arm11 bootrom checks cpuid and hangs if cpuid >= 2. This is a problem when booting the 2 additional New3DS Arm11 MPCores. NewKernel11 solves this by using a hardware feature to overlay the bootrom with a configurable branch to a kernel function. This overlay feature was added with the New3DS.

Bit1 in register above enables a bootrom data-override for physical addresses 0xFFFF0000-0xFFFF1000 and 0x10000-0x11000. All _data reads_ made to those regions now read the 32-bit value provided in [[CONFIG11 Registers #CFG11_BOOTROM_OVERLAY_VAL|CFG11_BOOTROM_OVERLAY_VAL]].

Bit1 in register above enables a bootrom data-override for physical addresses 0xFFFF0000-0xFFFF1000 and 0x10000-0x11000. All _data reads_ made to those regions now read the 32-bit value provided in [[CONFIG11 Registers #CFG11_BOOTROM_OVERLAY_VAL|CFG11_BOOTROM_OVERLAY_VAL]].

Bit0 enables a bootrom instruction-overlay which means that _instruction reads_ made to the bootrom region are overridden. We have not been able to dump what instructions are actually placed at bootrom by this switch (because reading the area only yields data-reads). Jumping randomly into the 0xFFFF0000-0xFFFF1000 region works fine and jumps to the value provided by the data overlay [[CONFIG11 Registers #CFG11_BOOTROM_OVERLAY_VAL|CFG11_BOOTROM_OVERLAY_VAL]]. Thus we may predict that the entire bootrom region is filled by:

Bit0 sets the core out of reset and enables a bootrom instruction-overlay which means that _instruction reads_ made to the bootrom region are overridden. We have not been able to dump what instructions are actually placed at bootrom by this switch (because reading the area only yields data-reads). Jumping randomly into the 0xFFFF0000-0xFFFF1000 region works fine and jumps to the value provided by the data overlay [[CONFIG11 Registers #CFG11_BOOTROM_OVERLAY_VAL|CFG11_BOOTROM_OVERLAY_VAL]]. Thus we may predict that the entire bootrom region is filled by:

ldr pc, [pc]

ldr pc, [pc]

Or equivalent. However, jumping to some high addresses such as 0xFFFF0FF0+ will crash the core. This may be explained by prefetching in the Arm pipeline, and might help us identify what instructions are placed by the instruction-overlay.

Or equivalent. However, jumping to some high addresses such as 0xFFFF0FF0+ will crash the core. This may be explained by prefetching in the Arm pipeline, and might help us identify what instructions are placed by the instruction-overlay.