Glorious CCCG thread -- Cellphone Compute Cluster for GIMPS

[ewmayer]

If someone does find a reasonably popular - as in, lots available on the 2ndary market, including cheap 'for parts' ones with e.g. screen damage but still usable as a compute node - phone model meeting the following criteria, by all means post it here:

1. Uses ARM-based compute core(s);
2. Runs Android or some other OS for which a Linux-emulation-environment app is available;
3. Batteries either reasonably easy to replace, or phone will operate without a working one.

European or other non-US-available models are OK, since the bare phones are small and thus reasonably cheap to ship internationally.

[xilman]

Originally Posted by ewmayer

If someone does find a reasonably popular - as in, lots available on the 2ndary market, including cheap 'for parts' ones with e.g. screen damage but still usable as a compute node - phone model meeting the following criteria, by all means post it here:

1. Uses ARM-based compute core(s);
2. Runs Android or some other OS for which a Linux-emulation-environment app is available;
3. Batteries either reasonably easy to replace, or phone will operate without a working one.

European or other non-US-available models are OK, since the bare phones are small and thus reasonably cheap to ship internationally.

A very quikc search shows that replacement batteries are between $15 and $25 on amazon. I do not know whether you regard that as a "cheap" way of keeping your existing farm running.

[ewmayer]

Originally Posted by xilman

A very quikc search shows that replacement batteries are between $15 and $25 on amazon. I do not know whether you regard that as a "cheap" way of keeping your existing farm running.

In my particular phones, replacing the battery is well-nigh impossible -- merely replacing the touchscreen is gnarly enough. Not worth the time/risk/effort for a device which provides less than 1% the GIMPS throughput of one of my Radeon VII GPUs and which cost < $50 to begin with.

The real solution for this sort of thing rests with the manufacturer - there is no good reason other than greed why they can't make products which:

1. Allow simpler common-repair-items such as screen and battery replacement;
2. Not insist on bricking products unless they have a working battery.

We should support manufacturers which do those things, hence my call for suggestions re. phone models meeting those criteria.

[kriesel]

Originally Posted by ewmayer

1. Allow simpler common-repair-items such as screen and battery replacement;
2. Not insist on bricking products unless they have a working battery.

It's no fun getting a phone bricked because the vitals got wet, either. Been there, had that, despite the protection of a "sealed" plastic container with dry cloth wrapped around the phone. The S7 adhesive everywhere is there as sealant against water getting in and creating electrolysis between components at different voltages. Phones with easy access removable components usually have moisture telltales inside, as in "you got it wet and voided your warranty and probably lost your contacts and other data too." Not likely an issue for cellphone compute, but a significant consideration for the original purchaser and the manufacturer.
So part of your search criteria may be for phones that are NOT water resistant.

[Nick]

Have you seen this list of Android smartphones with replacebale battery already?
https://thedroidguy.com/best-android...attery-1062773

[ewmayer]

Originally Posted by Nick

Have you seen this list of Android smartphones with replacebale battery already?
https://thedroidguy.com/best-android...attery-1062773

Thanks - Note that for cellphone computation, we don't need an easily replaceable battery so much as a model which allows the phone to operate hooked up to a charger even if the battery is dead.

Quick review of the list in your linked article:

o Galaxy S4 is 32-bit CPU, might be possible to get decent performance out of that -- on newer 64-bit CPUs non-SIMD builds get ~2/3 the throughput of ASIMD-using Mlucas build on the same CPU, likely because both modes share the same underlying 'lean' set of hardware resources, e.g. instead of having dedicated transistor-heavy SIMD multipliers, adders, etc as Intel has, ARM-bsed cores might have (say) 1 or 2 64-bit floating adders and multipliers, usable by both non-SIMD and ASIMD instructions -- but not worth the effort of the required 32-bit-supporting code changes.

o Xcover4 uses a 1.4GHz Quad-Core (Cortex-A53), that is 64-bit, but I retired my faster 2.0GHz A53-using Odroid C2 because it was taking months just to finish an a DC.

o Moto G5: Uses an octa-core 1.4 GHz Snapdragon 430 SoC, which means a bunch of telecom-related silicon and an Octocore 1.4GHz A53. Wikipedia notes the Moto G5 Plus uses a 2.0 GHz octocore A53 ... that might approach the crunching power of the CPUs in my Galaxy S7s.

o BLU VIVO X5: uses an octa-core Cortex A55 chipset, probably similar DFLOPS as the Moto G5.

[ewmayer]

Down to my last S7 broke-o-phone - batteries on all the rest no longer take sufficient charge to boot up. I would like to get rid of the 5-port USB charging station I used for these - my sister and her conencted household could use one - but I can't seem to find a USB port on any of my other devices which offers more than 500mA current - an S7 under full Mlucas-on-all-4-cores load needs between 1 and 2 A. If I could somehow gang together the power from 2 or more USB ports on one of the nearby devices, that would be very useful. Does anyone know if such reverse-Y-splitters for USB exist? My online search turned up nothing useful, all the splitters I found are the other way, splitting one into multiples.

[Uncwilly]

You should be able to get a 2.1A wall charger at your local 'dollar' store or the like. They may ask 4$USD or so. I have one that has a 2.1, a 1.0, and 2 standard AC outlets on the face (it takes 1 AC outlet).

[ewmayer]

Originally Posted by Uncwilly

You should be able to get a 2.1A wall charger at your local 'dollar' store or the like. They may ask 4$USD or so. I have one that has a 2.1, a 1.0, and 2 standard AC outlets on the face (it takes 1 AC outlet).

Thanks for jogging my memory - I have both a 1-usb and 2-usb wall charger on hand, the small-cube 1-usb has no labeling but trying that, if not enough juice will switch to the beefier 2-usb one, which is 2 x 2.4A, and thus should have more than enough. I only have short 6" USB-to-micro-USB adapter cables for use with the desktop charging station, so final ingredient needed to be able to still keep the phone on my desk is an adapter allowing me to hook up the USB-male end of that to another USB-male-to-USB-male cable. Luckily, I have just the needed adapter, so last-phone-standing plugged into 1-usb wall charger and back up and running, and a small bit of valuable desktop real estate recovered where the 5-port station was.