Undocumented SPU Channels
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Channels 64, 72 and 73
Used for storing the version.
Reading/writing the data:
void read_ch73(u32 skip, u32 *buf, u32 len) { u32 i; spu_wrch(64, 0x10000); for(i = 0; i < skip; i++) spu_rdch(73); for(i = 0; i < len; i++) buf[i] = spu_rdch(73); } void write_ch72(u32 skip, u32 *buf, u32 len) { u32 i: spu_wrch(64, 0x10000); for(i = 0; i < skip; i++) spu_wrch(72, spu_rdch(73)); for(i = 0; i < len; i++) spu_wrch(72, buf[i]); }
lv1ldr writes the version:
s64 lv1ldr_main(...) { //... u64 ldr_ver = 0x0003004100000000; write_ch72(0, &ldr_ver, 2); //... }
Other isolated binaries check the version:
s64 check_version(u64 ldr_ver) { u64 stored_ver; read_ch73(0, &stored_ver, 2); //... } s64 load_isoself(...) { ldr_ver = 0x0003004100000000; if(check_version(ldr_ver) != 0) return 0x30; //... }
Channel 74
Returns random data. Mostly used as a seed to feed a FIPS 186 PRNG with it.
Sample data (256 MB): https://mega.co.nz/#!gNc0hQrR!4rC-Stz5yqi7yqvp6OWOQcxB_XhlrOadoE_fE5fyDxE
A bitmap generated from RNG samples: