[OpenBIOS] PowerPC special purpose registers

[Programmingkid]

On May 2, 2016, at 6:53 PM, Segher Boessenkool wrote:

> On Mon, May 02, 2016 at 06:05:05PM -0400, Programmingkid wrote:
>> You know how you see messages about writing to missing registers like these:
>> 
>> OS 9.2] Trying to write invalid spr 0 (0x000) at 00f113c0
>> 11:26:23.910 WARNING [Mac OS 9.2] Trying to read invalid spr 0 (0x000) at 00f113c8
>> 11:26:24.055 WARNING [Mac OS 9.2] Trying to write privileged spr 955 (0x3bb) at 00f164b8
>> 11:26:24.055 WARNING [Mac OS 9.2] Trying to write invalid spr 959 (0x3bf) at 00f16520
>> 11:26:24.055 WARNING [Mac OS 9.2] Trying to read invalid spr 959 (0x3bf) at 00f16528
>> 11:26:24.056 WARNING [Mac OS 9.2] Trying to write invalid spr 944 (0x3b0) at 00f1653c
>> 11:26:24.056 WARNING [Mac OS 9.2] Trying to read invalid spr 944 (0x3b0) at 00f16544
>> 11:26:24.056 WARNING [Mac OS 9.2] Trying to write invalid spr 951 (0x3b7) at 00f16550
>> 11:26:24.056 WARNING [Mac OS 9.2] Trying to read invalid spr 951 (0x3b7) at 00f16558
>> 11:26:24.204 WARNING [Mac OS 9.2] Trying to write privileged spr 955 (0x3bb) at 00f164b8
>> 11:26:24.204 WARNING [Mac OS 9.2] Trying to write invalid spr 959 (0x3bf) at 00f16520
>> 11:26:24.204 WARNING [Mac OS 9.2] Trying to read invalid spr 959 (0x3bf) at 00f16528
>> 11:26:24.204 WARNING [Mac OS 9.2] Trying to write invalid spr 944 (0x3b0) at 00f1653c
>> 11:26:24.204 WARNING [Mac OS 9.2] Trying to read invalid spr 944 (0x3b0) at 00f16544
>> 11:26:24.205 WARNING [Mac OS 9.2] Trying to write invalid spr 951 (0x3b7) at 00f16550
>> 11:26:24.205 WARNING [Mac OS 9.2] Trying to read invalid spr 951 (0x3b7) at 00f16558
>> 
>> Should these registers be implemented? Maybe Apple expected these registers to be available on their hardware.
> 
> It is probing if the hardware has these registers here.  Nothing is wrong.
> We discussed this on irc for the gsoc thing...
> 
>> 944	Monitor Control Register 2
>> 951	Breakpoint Address Mask Register1
>> 955	Sampled Instruction Address 1 
>> 959	Sampled Data Address 		* PowerPC 604 only
> 
> 944 = MMCR2
> 951 = BAMR
> 955 = SIAR
> 959 = SDAR (not just 604, fwiw -- where did you read that?)

http://www.nxp.com/files/32bit/doc/data_sheet/MPC604.pdf
page 19

What is says: 604-specific—not defined by the PowerPC architecture

> 
> Yes.  And 0 is MQ (a 601 thing), etc.
> 
> Some CPUs have slightly different names for the same thing (prefer SIA
> to SIAR, etc.; some have different things at the same SPR #.  What OS9
> is doing here isn't exactly correct, but it is what it is.

Thank you very much for clearing this up. I have a feeling what
Apple did was not what the specifications would prefer.