Need Fuel L1 commands to change CPU PIMMs - Printable Version

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Need Fuel L1 commands to change CPU PIMMs - weblacky - 05-25-2020

Hi,
 Due to Nekochan's demise, there appears to no longer be any info related to altering the CPU speed settings on the SGI Fuel platform to prepare for PIMM replacement (upgrade or downgrade).  I know some of the old-timers will know how to do this.

Can someone please publish the technique to perform this.  I know it has to do with setting speed and timings in the L1...but no idea what commands to use.  We need this info published somewhere due to Fuels becoming more and more "parts" machines.  Switching CPUs will become a much bigger deal.

Can someone please post examples of this?

Thanks!

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RE: Need Fuel L1 commands to change CPU PIMMs - hamei - 05-25-2020

(05-25-2020, 12:31 AM)weblacky Wrote:  Can someone please publish the technique to perform this.  I know it has to do with setting speed and timings in the L1...but no idea what commands to use.  We need this info published somewhere due to Fuels becoming more and more "parts" machines.  Switching CPUs will become a much bigger deal.

As I remember, you can't.  The machine has to get through POST to get to where you can change the cpu speed, but if it is set too high, it won't. It's a case of "you can't get there from here."

The only way I was ever able to do this was stick a faster cpu in, set the speed down, then swap in the slower one. It's a one-way street.

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RE: Need Fuel L1 commands to change CPU PIMMs - weblacky - 05-25-2020

Hi,
Please post speed set commands, they don't exist anywhere but in someone's head right now.

Two counter points:

1. To speed down, you still need to do something on the L1. Can you please post the instructions?

2. It's not 100% known you cannot go other other way. Because there is evidence you can start the Fuel L1 without any PIMM installed in the machine:

https://gainos.org/~elf/sgi/nekonomicon/forum/3/16729947/1.html

Since no one has claimed (failure or success) to try getting the L1 to start without ANY PIMM, speeding down via commands to L1, then powering off, then installing a PIMM, we really don't know for sure (until it's tried) that you can't use this (no PIMM) loop hole to down-clock.

And if you can get it to start (via restart PSU roulette madness), it's unknown if (without the PIMM hardware present) whether the set commands would take affect/stick/remembered. But it's POSSIBLE, since the L1 has to remember what speed to use if you ever take out your PIMM and happen to power it on (it's not lost information).

So two unknowns, it might be possible to down-clock without an existing PIMM, point is...right now...we can't do anything, because no one has a post with the commands that I've found via google right now...Arc lost in the government warehouse...

Thanks,

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RE: Need Fuel L1 commands to change CPU PIMMs - hamei - 05-25-2020

(05-25-2020, 03:57 AM)weblacky Wrote:  Hi,
Please post speed set commands, they don't exist anywhere but in someone's head right now.

Two counter points:

1. To speed down, you still need to do something on the L1.  Can you please post the instructions?

2. It's not 100% known you cannot go other other way. Because there is evidence you can start the Fuel L1 without any PIMM installed in the machine:

It's been way too long, but you did NOT change cpu speeds from the L1. You did it from within Irix.

And the "L1 works without getting through POST" never really happened. Not that it matters because that's not where you change the cpu settings. There's no tool to do it that way.

Having tried this several times with top-quality help from people who knew what they were talking about, this is a waste of time. Not going to happen.

Your time, your decision, but ...

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RE: Need Fuel L1 commands to change CPU PIMMs - weblacky - 05-25-2020

Alright, Please post the Irix commands so we can lookup what they do.

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RE: Need Fuel L1 commands to change CPU PIMMs - Irinikus - 05-25-2020

Maybe this helps:

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RE: Need Fuel L1 commands to change CPU PIMMs - weblacky - 05-25-2020

Hi.
I saw this, please explain how this sets the PIMM clock speed to a user-specified value? I see the IOPORT command above this listing and it has some clock speeds and the clksrc sub-command, but they claimed it sets a bus speed between 400Mhz or 600Mhz? I don't think this changes the CPU multiplier, nor the base CPU speed.

Did you find any examples to help illustrate how to use these to up-clock/down-clock from existing PIMM to new PIMM.

Thanks!

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RE: Need Fuel L1 commands to change CPU PIMMs - Irinikus - 05-25-2020

I don't have any experience here, but maybe if you select the pimm's clock to be internal, it will reset the nvram value to that of the new pimm?

Just a thought.

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RE: Need Fuel L1 commands to change CPU PIMMs - indy99 - 06-21-2020

weblacky Wrote: Due to Nekochan's demise, there appears to no longer be any info related to altering the CPU speed settings on the SGI Fuel platform to prepare for PIMM replacement (upgrade or downgrade).  I know some of the old-timers will know how to do this.

Can someone please publish the technique to perform this.  I know it has to do with setting speed and timings in the L1...but no idea what commands to use.

Don't believe it's possible to do this via the L1.  The methods I've successfully used are via POD mode in the PROM, and by using the IRIX flash command.  Between those IRIX flash is the relatively safest method, mostly because it has some publicly available documentation.

man flash Wrote:flash(1m)   


-f   Specify different (than currently in PROM) configurations
  values to be used when the new images are flashed.  These
  values include the speed of the CPU, hub, and size of the
  cache.  This option should be used with great care as cause
  the machine to freeze and be rendered unusable if incorrect
  values are given.

Make the changes with the currently clocked cpu in place, shut down and install the new PIMM.  The system will reboot expecting to find a CPU with *exactly* the values you specified, so a simple syntax error can be fatal.  Make sure you have all of the required parameters for the incoming PIMM ready to insert before you attempt the flash.

I've also did it once from POD mode, but it's been long enough ago I won't trust my memory to lead you into a non-recoverable dead end.  

Either was you go you should be prepared for at least a semi-white knuckled experience.  If it goes south I don't know of publicly discussed method of recovery.

As far as downclocking goes I have zero experience, but I'm pretty sure someone on nekochan crashed and burned trying it. On the other hand as long as the new (faster) PIMM is capable of running at the slower values in the PROM you might be ok. A number of people posted on nekochan asking why their newly installed 600mHz PIMM still showed up as a 500mHz in an hinv, and were able to successfully flash the new values post install.  So going from slower to faster might be recoverable after the fact.

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RE: Need Fuel L1 commands to change CPU PIMMs - hamei - 06-21-2020

(06-21-2020, 06:12 PM)indy99 Wrote:  As far as downclocking goes I have zero experience, but I'm pretty sure someone on nekochan crashed and burned trying it. On the other hand as long as the new (faster) PIMM is capable of running at the slower values in the PROM you might be ok. A number of people posted on nekochan asking why their newly installed 600mHz PIMM still showed up as a 500mHz in an hinv, and were able to successfully flash the new values post install.  So going from slower to faster might be recoverable after the fact.

You can downclock, it's the only way I know of to make a mainboard run with a slower cpu. But you have to remember to do it with the faster cpu installed, cuz if you ship the board to someone with a 600 and you've been running it at 800, it's an oops :-(  and you can't do it with no pimm or a slower one installed cuz it won't boot. Catch-22.

Not that I've ever done that, you understand, but that's what I hear ...

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