headamage
Posts: 75
Joined: Wed Jan 07, 2015 9:59 am

Re: Faulty Pi Memory

Sat Mar 14, 2015 6:17 pm

Update:

The "bad" Pi has passed my mprime.py with

arm_freq=900
core_freq=500
over_voltage=0
sdram_freq=500

The memory seems to be fine at those clocks so I lost my money on the guess I made previously (i was so confident and i ate a humble Pi :p). The CPU seems to be the problem. Will try increasing CPU clock slowly to find out the limit but it seems like my Pi has a CPU that is running very close to its stable limit.

headamage
Posts: 75
Joined: Wed Jan 07, 2015 9:59 am

Re: Faulty Pi Memory

Sat Mar 14, 2015 7:04 pm

OK so the "bad" Pi cannot do much above 950MHz no matter the voltage. I used default values for RAM and core.

It passed my prime test with:

arm_freq=950
over_voltage=2

The other Pi is much more flexible and it can do stable 1GHz as posted previously.
It seems like the CPU in the "bad" Pi is already running close to its limit but with enough headroom to ensure it is very stable at 900MHz.

So the only problem to report is that the raspi-config preset for Pi2 @1GHz is not stable on either of my devices. I decided not to overclock the CPU on either Pi and stick to core and RAM overclocking instead which has not caused any problems so far.

jamesh
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Re: Faulty Pi Memory

Sat Mar 14, 2015 8:07 pm

I'd replace the word 'bad' with 'not as good'!!!
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed.
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headamage
Posts: 75
Joined: Wed Jan 07, 2015 9:59 am

Re: Faulty Pi Memory

Sat Mar 14, 2015 8:19 pm

jamesh wrote:I'd replace the word 'bad' with 'not as good'!!!
Haha! Indeed the Pi is not "bad", just not as "sweet" as the other Pi. No extra sugar in that one. But yes, the Pi is indeed operating according to spec, so I can't complain. I cancelled the RMA as there is no point going through the process for 100MHz overclock considering that all the other parameters can be overclocked without problems.
I have now run several loops of my prime sieve script and it runs without fail on both Pi:

arm_freq=900
core_freq=500
sdram_freq=500
over_voltage=2 (just in case)

But this guy had the same problem as me with his raspi-config overclock:
http://linuxonflash.blogspot.co.uk/2015 ... mance.html

How do you determine the suggested overclock presets for raspi-config? I was under the impression that they are guaranteed to work. Did the original Pi have similar problems with the presets? I have given my Pi B+ to a student for a project and I can't test it but it never failed my prime test even at 1GHz overclock from the raspi-config preset. I never tried a memtest though. When I get it back, I will do a set of tests on it.

ktb
Posts: 1447
Joined: Fri Dec 26, 2014 7:53 pm

Re: Faulty Pi Memory

Sat Mar 14, 2015 8:54 pm

My B+ will do 1200 reliably and I can get core, h264, isp and v3d all up to at least 525 without any problems.

My Pi2B really can't reliably go over ~1100 and no matter what I've tried I am not able to get the h264 clock to go over ~250 (core, isp, v3d will all go to 500 or beyond). I figure this limitation is specific to my Pi2B as I've not seen any other mentions of only the h264 clock speed having a limitation.

Oh well. Not all Pi's are created equal. I'm still happy to have the Pi2B.

headamage
Posts: 75
Joined: Wed Jan 07, 2015 9:59 am

Re: Faulty Pi Memory

Sat Mar 14, 2015 11:15 pm

ktb wrote:My B+ will do 1200 reliably and I can get core, h264, isp and v3d all up to at least 525 without any problems.

My Pi2B really can't reliably go over ~1100 and no matter what I've tried I am not able to get the h264 clock to go over ~250 (core, isp, v3d will all go to 500 or beyond). I figure this limitation is specific to my Pi2B as I've not seen any other mentions of only the h264 clock speed having a limitation.

Oh well. Not all Pi's are created equal. I'm still happy to have the Pi2B.
give me prime sieve script a run with a range between 10000 - 15000 or greater numbers and 4 threads. it really hammers the RAM and CPU at the same time. It uses Wilson's prime theorem which calculates the factorial of each number it checks to determine if it is prime. 4 cores calculating factorials of large numbers gets things pretty hot pretty fast.

rpiswag
Posts: 804
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Re: Faulty Pi Memory

Sun Mar 15, 2015 6:08 am

I am so happy the Pi is ok and didn't have a problem! :D
A computer's power can't be just measured Gigahertz. It is the same thing with us humans.

jamesh
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Re: Faulty Pi Memory

Sun Mar 15, 2015 9:50 am

The Pi2 generally cannot be overclocked as fast as the Pi1, for various reasons. Which I cannot remember although had been told at some point in the past.

The guaranteed clock value is the default, no overclocks are guaranteed. The overclock setting for Pi2 in the setup is a value that will usually work for the huge majority of Pi2's. Some will go faster, and a very few won't be able to make that overclock. It's all due to the manufacturing process, which despite billion dollar fabs is still does not result in exactly the same results for every device.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
Contrary to popular belief, humorous signatures are allowed.
I've been saying "Mucho" to my Spanish friend a lot more lately. It means a lot to him.

hglm
Posts: 30
Joined: Fri May 31, 2013 8:24 pm

Re: Faulty Pi Memory

Sun Mar 15, 2015 2:43 pm

jamesh wrote:The Pi2 generally cannot be overclocked as fast as the Pi1, for various reasons. Which I cannot remember although had been told at some point in the past.
The Raspberry Pi 2 processor chip uses entirely different ARM processor cores and an entirely different type of RAM. Considering this significant differences in attainable clock speeds are understandable. But of course the Pi 2 is considerably faster than the Pi 1 at the same clock speed, so it doesn't really matter.

The RAM is completely different on the Raspberry Pi 2. The Pi 1 uses relatively fast RAM chips embedded on the processor SoC package, which can be clocked up to 600 MHz in many cases (as reflected by the available overclocks for the Pi).

However, the Pi 2 (at least my device) uses external SDRAM chips that are only officially specified for 400 MHz. It is no surprise that this makes SDRAM clock speeds of 500 MHz or higher difficult to achieve reliably.
The guaranteed clock value is the default, no overclocks are guaranteed. The overclock setting for Pi2 in the setup is a value that will usually work for the huge majority of Pi2's. Some will go faster, and a very few won't be able to make that overclock. It's all due to the manufacturing process, which despite billion dollar fabs is still does not result in exactly the same results for every device.
I have the impression that more than just a few Pi 2's won't handle the default available overclock setting in raspi-config for the Pi 2 when faced with a rigorous stress test (such as running memtester in parallel or the prime calculation mentioned in this thread). That is not a big problem, but I feel there should overclocks available in raspi-config that reliably work on a greater percentage of Raspberry Pi 2's, which I believe is easy to achieve (for example, SDRAM could be clocked a little lower than 500 MHz given the nature of the SDRAM chips on the Pi 2).

What is also missing is an option in raspi-config to reset the default clock speeds of the Raspberry Pi 2, like there is for the Pi 1. This leads to confusion, as is clear from this thread (such as option would be easier to use and more obvious than having to manually remove/comment out the overclock settings in /boot/config.txt).

Finally, the default core clock speed of the Rasperry Pi 2 (250 MHz) is conservative and seems to constrain performance. On the Raspberry Pi 2, unlike the Pi 1, core_freq has little effect on the GPU but instead seems to govern the L2 CPU cache speed. This is a critical part of overall processor performance, and since experience shows that many Pi 2 processor chips can handle L2 cache (core_freq) speed up to 600 MHz, 250 MHz seems rather on the low side.

headamage
Posts: 75
Joined: Wed Jan 07, 2015 9:59 am

Re: Faulty Pi Memory

Sun Mar 15, 2015 3:08 pm

I would agree. The two lessons to take from this experience is that raspi-config need a default setting for Pi2 like it has for Pi1. It also needs some overclocking presets for Pi2 that cover a wider range of scenarios. At the moment, the only option we have is a preset that seems a bit "extreme" based on my findings and what i read on the internet and at the same time there is no preset to go back to default clocks! That's the biggest problem because for new users there is no way to undo a bad choice without editing /boot/config.txt which is something that may appear scary for a new user. Please don't treat the Pi2 as a second class citizen in the overclocking options in raspi-config. Give it a comprehensive section that covers a wide range of presets and more importantly, a factory default clock option.

And many thanks for putting your attention on my findings. Hopefully it will help in developing the platform further.

gsh
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Re: Faulty Pi Memory

Sun Mar 15, 2015 7:54 pm

Any overclock settings are not guaranteed to work. The default settings for Pi 2 is a standard frequency of 700MHz with a turbo of 900MHz (the linux system will automatically switch up to 900MHz as soon as you're using a fair amount of one core.

At Raspberry Pi we try very hard (very very hard) to make our software test the Raspberry Pi to the extent where the failure rate in the field is dropping to < 0.01% that applies to both UK and PRC Pis and we (I) spend a great deal of time making sure that the tests are testing the right thing and that no errors get out of the door!

If you're running it above 900MHz then all bets are off, the numbers in raspi-config are different values that some people have found work on their Pis nothing more.

Gordon
--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

ktb
Posts: 1447
Joined: Fri Dec 26, 2014 7:53 pm

Re: Faulty Pi Memory

Mon Mar 16, 2015 10:12 am

headamage wrote:
ktb wrote:My B+ will do 1200 reliably and I can get core, h264, isp and v3d all up to at least 525 without any problems.

My Pi2B really can't reliably go over ~1100 and no matter what I've tried I am not able to get the h264 clock to go over ~250 (core, isp, v3d will all go to 500 or beyond). I figure this limitation is specific to my Pi2B as I've not seen any other mentions of only the h264 clock speed having a limitation.

Oh well. Not all Pi's are created equal. I'm still happy to have the Pi2B.
give me prime sieve script a run with a range between 10000 - 15000 or greater numbers and 4 threads. it really hammers the RAM and CPU at the same time. It uses Wilson's prime theorem which calculates the factorial of each number it checks to determine if it is prime. 4 cores calculating factorials of large numbers gets things pretty hot pretty fast.
Image

headamage
Posts: 75
Joined: Wed Jan 07, 2015 9:59 am

Re: Faulty Pi Memory

Mon Mar 16, 2015 11:14 am

ktb wrote:
headamage wrote:
ktb wrote:My B+ will do 1200 reliably and I can get core, h264, isp and v3d all up to at least 525 without any problems.

My Pi2B really can't reliably go over ~1100 and no matter what I've tried I am not able to get the h264 clock to go over ~250 (core, isp, v3d will all go to 500 or beyond). I figure this limitation is specific to my Pi2B as I've not seen any other mentions of only the h264 clock speed having a limitation.

Oh well. Not all Pi's are created equal. I'm still happy to have the Pi2B.
give me prime sieve script a run with a range between 10000 - 15000 or greater numbers and 4 threads. it really hammers the RAM and CPU at the same time. It uses Wilson's prime theorem which calculates the factorial of each number it checks to determine if it is prime. 4 cores calculating factorials of large numbers gets things pretty hot pretty fast.
Image
sweet! what is this GUI you are using? Can i get it somehow or is it customised by you?

ktb
Posts: 1447
Joined: Fri Dec 26, 2014 7:53 pm

Re: Faulty Pi Memory

Mon Mar 16, 2015 11:33 am

It's just LXDE with conky (combined with some shell and python scripts) on the side. I use the Numix theme and just flip the background and foreground colors using LXAppearance (Customize Look and Feel). Obconf might help adjust things too.
https://github.com/shimmerproject/Numix
https://github.com/numixproject/numix-icon-theme

headamage
Posts: 75
Joined: Wed Jan 07, 2015 9:59 am

Re: Faulty Pi Memory

Mon Mar 16, 2015 11:38 am

ktb wrote:It's just LXDE with conky (combined with some shell and python scripts) on the side. I use the Numix theme and just flip the background and foreground colors using LXAppearance (Customize Look and Feel). Obconf might help adjust things too.
https://github.com/shimmerproject/Numix
https://github.com/numixproject/numix-icon-theme
thanks, will give it a try.

ktb
Posts: 1447
Joined: Fri Dec 26, 2014 7:53 pm

Re: Faulty Pi Memory

Thu Apr 02, 2015 6:18 am

ktb wrote:My B+ will do 1200 reliably and I can get core, h264, isp and v3d all up to at least 525 without any problems.

My Pi2B really can't reliably go over ~1100 and no matter what I've tried I am not able to get the h264 clock to go over ~250 (core, isp, v3d will all go to 500 or beyond). I figure this limitation is specific to my Pi2B as I've not seen any other mentions of only the h264 clock speed having a limitation.

Oh well. Not all Pi's are created equal. I'm still happy to have the Pi2B.
Update: Somehow for the first time I've been able to get the H264 clock up to 500. It seems that by lowering sdram_freq from 500 to 483, the H264 clock is no longer limited at 250. It's weird, but I guess I don't really care what causes that to happen.

adamdbz
Posts: 15
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Re: Faulty Pi Memory

Wed May 13, 2015 11:20 am

Just did the
sudo memtester
on stock it passes
on the pi2 overclock it failed.

i think i should lower the ram to 480mhz.

jaroslav.henzely
Posts: 5
Joined: Thu May 14, 2015 7:52 pm

Re: Faulty Pi Memory

Thu May 14, 2015 8:08 pm

Hello,
I got also failures with memtester, see the output below.
My model is Raspberry Pi 2, Made in UK, Elpida RAM
Check this one:
Bit Flip : testing 168FAILURE: 0xffdfffff != 0xffffffff at offset 0x07027120.

Code: Select all

root@PI:/# memtester 256M 1
memtester version 4.2.2 (32-bit)
Copyright (C) 2010 Charles Cazabon.
Licensed under the GNU General Public License version 2 (only).

pagesize is 4096
pagesizemask is 0xfffff000
want 256MB (268435456 bytes)
got  256MB (268435456 bytes), trying mlock ...locked.
Loop 1/1:
  Stuck Address       : ok         
  Random Value        : ok
  Compare XOR         : ok
  Compare SUB         : ok
  Compare MUL         : ok
  Compare DIV         : ok
  Compare OR          : ok
  Compare AND         : ok
  Sequential Increment: ok
  Solid Bits          : ok         
  Block Sequential    : ok         
  Checkerboard        : ok         
  Bit Spread          : ok         
  Bit Flip            : testing 168FAILURE: 0xffdfffff != 0xffffffff at offset 0x07027120.
  Walking Ones        : ok         
  Walking Zeroes      : ok         
  8-bit Writes        : ok
  16-bit Writes       : ok

Done.
Tested without RAM overclock.
Thanks for Your help.

AnAkkk
Posts: 5
Joined: Sat Aug 22, 2015 7:50 pm

Re: Faulty Pi Memory

Mon Aug 24, 2015 10:00 pm

I have exactly the same issue with the Pi2 overclock settings, a lot of errors in memtester.
I tried to lower the SDRAM clock 480 MHz and even 470 MHz, but I still get a few errors.
headamage: have you actually been able to test if changing over_voltage_sdram has any effect on the issue (rather than changing arm_freq and/or over_voltage?

e-raser
Posts: 71
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Re: Faulty Pi Memory

Thu Sep 08, 2016 4:57 pm

No news (?) - that's probably bad news. :(
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texy
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Re: Faulty Pi Memory

Fri Sep 09, 2016 8:20 am

e-raser wrote:No news (?) - that's probably bad news. :(
There is no news because there is no news to report. It is not a fault condition - please re-read the post from Gordon above.
Texy
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https://www.raspberrypi.org/forums/viewtopic.php?f=93&t=147682#p971555

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