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open-power / hostboot

System initialization firmware for Power systems
Apache License 2.0
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Bit of an explanation on this line. #181

Open hanetzer opened 5 years ago

hanetzer commented 5 years ago

https://github.com/open-power/hostboot/blob/5825828fa7984e6d46dd47ef1835646303d2a593/src/kernel/start.S#L36 So, this line says it clears MSR[TA] (bit 1) but Power ISA Version 3.0 B pg. 943 states that bits 1-2 of the MSR are 'reserved', and there is no bit I can see called TA. I was hoping someone could elaborate on this, or let me know I'm interpreting it wrong.

npiggin commented 5 years ago

You are reading the ISA correctly, these MSR bits are reserved. It predates my involvement with OpenPOWER but the code or comment may have inadvertently come from some legacy code base or documentation.

dcrowell77 commented 5 years ago

Remember that the Power ISA AS permits implementation-specific extensions to the architecture. At this point I can only tell you that bit 1 does need to be zero for Hostboot and OPAL.

dcrowell77 commented 5 years ago

FYI - https://www.techrepublic.com/article/open-source-power-isa-takes-aim-at-intel-and-arm-for-accelerator-driven-computing/

Things might be getting a bit more open going forward.

friedkiwi commented 5 years ago

@hanetzer see https://archive.midrange.com/mi400/200502/msg00004.html for a good starting point. You might want to plow through that mailing list archive if you want to know more about tags active mode.

hlandau commented 5 years ago

@hanetzer See here: https://www.devever.net/~hl/ppcas

hanetzer commented 5 years ago

@hanetzer see https://archive.midrange.com/mi400/200502/msg00004.html for a good starting point. You might want to plow through that mailing list archive if you want to know more about tags active mode.

Will do, thanks.

@hanetzer See here: https://www.devever.net/~hl/ppcas

Thankya, I actually have this open in a tab at my home workstation.

friedkiwi commented 5 years ago

@hanetzer: if you want to play with IBM i you can always pop into ##ibmi on freenode or on r/IBMiHUG. There’s a few semi-public machines people operate.