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Idea: Moving caches to SDRAM
#1
Hello all,

It seems that moving cache files to SDRAM improve sound quality.
I wrote howto:
https://qiita.com/tinyreminder/items/cc1...cdf321ff51

I would like to know your impression.

Thanks in advance,
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#2
What uses

/home/pi/.cache

I'd be tempted to leave logging as it is, for forensic purposes after any OS crashes and reboots.

Does changing each of the tmp and .cache directories one at a time make an audible difference?

Which of those three is most effective, and does changing them all make a noticeable difference over just changing .cache?

Cheers,

Phil

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#3
(08-05-2020, 05:52 AM)tinyreminder Wrote: Hello all,

It seems that moving cache files to SDRAM improve sound quality.

You lost me right there. Carl Sagan said it best "extraordinary claims require extraordinary evidence." [1] 

Specifically, what improvement in sound quality is to be expected?

Ummm, let me see. I'm playing a track right now in a moOde 6.7.1 installation. There's not /home/pi/.cache in the file system and I don't see current time stamps on files in the other directories mentioned in your howto. Just to be sure, I installed lsof and I don't see any running process with an open file in those directories.

Color me skeptical.

Regards,
Kent

[1] well, actually, Carl said it best in English. The famous mathematician and proto-mathematical physicist Pierre-Simon Laplace said essentially the same thing in French 200 years earlier.
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#4
/home/pi/.cache will be created after chromium-browser is started.
Enjoy the Music!
moodeaudio.org | Twitter Feed | Git Repo
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#5
You also can run moode on an overlay, that way the whole system will be sort of read only, and all changes will go on RAM.

U can easily do that with sudo raspi-config - advanced option - overlay FS

U also preserve SDcard lifetime that way, and no one can break ur installation since all changes are gone after a reboot.
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#6
(08-05-2020, 02:55 PM)Tim Curtis Wrote: /home/pi/.cache will be created after chromium-browser is started.


Ah. of course.

OTOH, if R/W cycles to that directory are somehow implicated, it could be a problem only when the local display is in use. Has any moOde user ever remarked on experiencing a diminution in sound quality when they enable the local display?

Regards,
Kent
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#7
(08-05-2020, 12:55 PM)philrandal Wrote: What uses

/home/pi/.cache

I'd be tempted to leave logging as it is, for forensic purposes after any OS crashes and reboots.

Does changing each of the tmp and .cache directories one at a time make an audible difference?

Which of those three is most effective, and does changing them all make a noticeable difference over just changing .cache?

Cheers,

Phil

Sorry, the entry I wrote is bit old.
Moving /var/log to SDRAM causes lots of problem.

In my opnion, moving /var/cache to SDRAM causes difference.
To try, add the line
Code:
tmpfs           /var/cache      tmpfs   defaults,size=500m,noatime      0       0
to end of /etc/fstab.

Moving other tmp directories such as /tmp and /var/tmp to SDRAM seems not to cause difference
but I think it helps to improve SD card lifetime.

Regards,
Takeshi
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#8
Thank you so much für your advice Smile
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#9
I tried moving /var/cache to RAM and could hear no difference in audio quality on my system (Pi2Design 502DAC Pro feeding 2 Modulus-86 amplifiers which power full range Fostex FE126En drivers in the Fostex suggested hybrid horn/bass reflex cabinets, also Pioneer SE-305s driven straight from the Pi2Design DAC). I'm sticking with it though, purely for SD card wear reasons, as I do find SD card problems to be the most frequent causes of the issues I've had with Raspberry Pis over the years.
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#10
Update: this seems to be a bad idea on a 1GB Raspberry Pi, having /var/cache in RAM was causing my system to become unresponsive and there were kernel messages relating to memory allocation errors. I reverted and these problems have gone away. YMMV and maybe it works better on the Pi 4s with more RAM, or without the local display enabled, but I definitely wouldn't recommend it on the older Pis.
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