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Messages - ejfluhr

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1
Mod Zone / Re: Custom cooler mount
« on: September 11, 2023, 09:12:02 pm »
>For stability testing I ran this machine hard for multi-day cycles (one of my own tools that 100% loads the CPU cores with lots of maths).

Do you know how "hot" that workload is compared to the TDP rating of the processor? 

Regards, Eric

2
Mod Zone / Re: Custom cooler mount
« on: August 17, 2023, 11:02:38 am »
Do you have any idea how much force you are applying down through the module to the socket pins?   IBM has a target pressure to ensure even and reliable contacting across all pins for the life of the processor given certain assumptions about electrical loads (e.g. amps thru pins) and thermal cycling.   It would be interesting to know if your solutions are approximately the same, or much higher or lower.

3
Firmware / Re: Updating Talos II firmware to IBM PNOR V2.18?
« on: April 17, 2023, 05:44:57 pm »
The 18c & 22c parts are "paired" meaning 2 SMT4 cores share the same L2 & L3, unlike the 4c and 8c which are "unpaired" meaning each core gets the full L2 and L3 to itself.    This is not the same as "fused" (i.e. SMT8 cores) but it is quite likely that the fix will also work for "paired" cores as presumably the issue is sharing cacheable/non-cacheable pathways.   Good luck!

4
Mod Zone / Re: Initial findings running on water cooling
« on: March 30, 2023, 07:59:11 pm »
That is awesome.    Do you know what the power difference is running the same benchmark air-cooled vs. water-cooled?

Are you thinking of boosting frequency higher on the CPU since it is running cooler & lower power?

5
Firmware / Re: Updating Talos II firmware to IBM PNOR V2.18?
« on: March 14, 2023, 06:05:09 pm »
I believe that all OpenPOWER/OPAL-based systems use SMT4 cores, not SMT8 (i.e. "fused") cores.    So that may mean you aren't seeing the same problem.

Do you get the same fault callout?

6
Blackbird / Re: Blackbird Cooling
« on: October 18, 2022, 01:02:27 am »
https://www.infineon.com/cms/en/product/power/dc-dc-converters/integrated-power-stages/tda21472/

It looks like that VRM is rated at 60A - 70A in typical ambient temps (e.g. < 40C).   It seems like there must be at least 2 in parallel on VDD, for a capacity of 120+A?   Efficiency falls off as the load gets that high, though.  It would be better to have 3 such stages so they draw only 30A - 40A under normal operation.

7
Firmware / Re: Messing with WOF Tables
« on: October 10, 2022, 05:58:15 pm »
>Basically you have the 8-core that Raptor sells but with the paired cores still on

What a neat observation!   Something to consider is that 160W at 2.5GHz is probably achieved at much lower VDD than the 8c 160W at 3.45GHz (https://raptorcs.com/content/CP9M32/intro.html).

P=IxV  =>  160W = I_3.45 x V_3.45 = I_2.5 x V_2.5

If voltage moves 1:1 with frequency (I don't know if it does, could be 1:2 or 2:1, but got to start somewhere), then 3.45GHz/2.5GHz = 1.38x.   So V_3.45 = V_2.5 x 1.38, alternatively V_2.5 = V_3.45 / 1.38.

So if P is constant, and V_2.5 is that much below V_3.45, then I_2.5 has to be increased by 1.38.

This is probably why the Blackbird wiki states:  Other CPUs (CPUs with a TDP greater than 160W) may operate without WoF due to power regulator limitations.

Even without WOF (i.e. at the base of 2.5GHz), you are probably pushing those regulators much harder than the 8c module does.

I couldn't find any information on how much VDD current the Blackbird regulators can support.  In the post by user deepblue, graphs indicate the processor was exceeding VDD load of 130A at 0.89v under some load.    Doing stupid translation to 16c just to see where that lands is (130A / 18c) x 16c ~= 115, presumably lower as the 18c is 190W and the 16c is 160W.   If your temps are running high, then perhaps the regs are only built to support ~100A and you are at or over that spec...


8
Firmware / Re: Messing with WOF Tables
« on: October 07, 2022, 05:58:39 pm »
I copied that table CSV from GIT and filtered it to generate plots of frequency versus "CORE_CEFF" for a couple of different "VRATIO" values.
This link declares:  https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.54.905&rep=rep1&type=pdf

     Power ~= VDD2 x Fclk x Ceff
     where the effective switched capacitance, Ceff, is commonly expressed as the product of the physical capacitance CL, and the activity weighting factor α, each averaged over the N nodes.

I don't know how you can identify what "CORE_CEFF" is in your processor, but the equation shows how that correlates to power.  I.e. smaller Ceff equals lower power.
Then the plot looks meaningful since the lowest frequency is at the highest CORE_CEFF and the frequency climbs as CORE_CEFF gets smaller, up to some limit.
Since the largest value of CORE_CEFF in the table is 1.0, that would be the highest power condition presumably associated with the 160W power rating of the table/processor.

I could not figure out how to post an image of the graphs, nor will the forum let me post the XLSX file with base data plus graphing tab, since it is too big.   So I deleted a bunch of rows from the base data that had "NEST_CEFF" > 0.25.   This let me shrink the XLSX file enough to post it.   

The first tab is the CSV data as posted.  The second tab "Plotme" is a filter + graph that can be manipulated by the red-colored cells; one variable showing a big difference is the VRATIO which can be modified by adjusting the VRATIO_INDEX box in integer values from 0 to 23 (the table has entries for all of those).  The other 2 tabs are copies of the Plotme tab with just the values & graphs at VRATIO=1.0 and VRATIO=0.7498; this let me save and review them side-by-side.   You could probably get fancy and plot all the variations on a single graph but I didn't care to go that far.

I picked VRATIO=1.0 and VRATIO=0.7948 because the maximum frequency changes substantially between all those values, starting at 3.4GHz and climbing to 3.8GHz.  You can play with the VRATIO_INDEX in the Plotme tab and see how the frequency curve continues to increase at different CORE_CEFF values, though always capped to that 3.8GHz. 

Raptor quotes the 190W 18-Core CPU as:  2.8GHz - 3.8GHz, so presumably you now have a 160W 16-Core CPU  of 2.5GHz - 3.8GHz.
https://raptorcs.com/content/CP9M36/intro.html
   CP9M36
   IBM POWER9 v2 CPU (18-Core)
       18 cores per package
           2.8GHz base / 3.8GHz turbo (WoF)
           190W TDP

User @deepblue was running an 18-Core CPU on a Blackbird mainboard, though with extra cooling:
   https://forums.raptorcs.com/index.php/topic,99.0.html
Hopefully you will find out if, long term, the Blackbird can handle a 16-core P9 when it matches the TDP of the supported 8-core version.

Nice work!   Please report back in a few months....


9
Firmware / Re: Messing with WOF Tables
« on: October 07, 2022, 01:55:37 pm »
Too bad this isn't publicly available:
   https://research.ibm.com/publications/deterministic-frequency-boost-and-voltage-enhancements-on-the-power10tm-processor

Abstract
Digital droop sensors with core throttling mitigate microprocessor voltage droops and enable a voltage control loop (undervolting) to offset loadline uplift plus noise effects, protecting reliability VDDMAX.  These combine with a runtime algorithm for Workload Optimized Frequency (WOF) that deterministically maximizes core frequency.  The combined effect is demonstrated across a range of workloads including SPECTM , and provides up to a 15% frequency boost and a 10% reduction in core voltage.


10
Firmware / Re: Messing with WOF Tables
« on: October 07, 2022, 01:19:54 pm »
Can you read out the processor frequencies and tell if it is boosting properly?    Do you see ~160W when at idle?   What about when running max threads off some heavy workload (e.g. Mersenne primes is a good one)?

11
General CPU Discussion / Re: Asymmetric CPUs with the Same Core Count
« on: October 07, 2022, 01:05:39 pm »
500MHz affords 1/500Mhz = 2ns resolution of latency?   Sounds cool!   What is same-die typical memory latency, ~70ns??   Local L3 would have to run on the order of ~10ns??

There could be sensitivity to core frequency, presuming the L3 cache and some of the internal transfer network is pipelined.  E.g. running at 3.8GHz turbo will give a better answer than 2.8GHz base.

12
Talos II / Re: Temperatures and rotational speed of fans
« on: October 07, 2022, 12:59:25 pm »
The processor OCC firmware can call for fan speed increases if on-die Tj rise.

Where does that "Temperature Pcie" come from?   Presuming it is from PCIe card(s), it would seem sensible that the BMC should monitor and adjust accordingly.   Hard to imagine there is such a glaring bug in the BMC firmware, but worse has happened I guess.

Maybe Fan5 is supposed to cool the PCIe cards, but isn't working?


13
General CPU Discussion / Re: Asymmetric CPUs with the Same Core Count
« on: September 30, 2022, 06:11:02 pm »
> The graph is a measurement of how long it takes to send a message between cores,

Aha, that was a major piece of info I did not grasp.   Your other explanations all coincide nicely now with the picture.  Pretty interesting measurement!

Do you, or anyone, know if anyone has made similar type of measurement on memory latency, including caching effects, from a single core to all memory in the system?

14
General CPU Discussion / Re: Asymmetric CPUs with the Same Core Count
« on: September 29, 2022, 05:18:26 pm »
Does that indicate the caching benefit?   E.g. is the darkest purple runs from the local L2, hence is the lowest latency?  Then the light-but-still-solid purple runs from the shared 10MB-L3 so has the next lowest latency.  The red/purple mix is going out to DIMM memory attached to the same die so it has yet greater latency, and finally the orange is DIMM memory on the other die, hence hops across the socket-to-socket link and has the largest latency.

I don't get why some dark-purple boxes are bigger than others, though.  Also why do some have the solid-light purple around them but not all?  It doesn't all line up.

15
General CPU Discussion / Re: Asymmetric CPUs with the Same Core Count
« on: September 20, 2022, 08:30:16 pm »
How do you read the purple and orange plot??

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