Raspberry Pi 4 Model B announced

[ewmayer]

Note Luigi (a.k.a. ET) also started a Pi4 thread in the Software/Mlucas subforum.

Originally Posted by paulunderwood

I have seen a Debian Buster PREVIEW image in the net for the 3B+. So I think it would not be very long after Buster is released that there will be a image for the Pi 4B.

For anyone planning to run Mlucas on a Pi4, you'll want a 64-bit Linux because the Mlucas SIMD build requires it.

[hansl]

There is a good detailed writeup of the specs, differences etc here:
https://cdn.shopify.com/s/files/1/15...berry_Pi_4.pdf

[hansl]

So I know its relatively simple to over/underclock the rPi with some config changes, and this got me wondering: if the GPU is not useful to GIMPS, and heat/power consumption is an issue, then is there a way to completely disable the GPU, or if not, how severely can it be underclocked, and would this help much?

[nomead]

Originally Posted by hansl

So I know its relatively simple to over/underclock the rPi with some config changes, and this got me wondering: if the GPU is not useful to GIMPS, and heat/power consumption is an issue, then is there a way to completely disable the GPU, or if not, how severely can it be underclocked, and would this help much?

I suspect the BCM2711 is similar to the earlier RPi processors in that the GPU is actually the primary processor on the SoC and the ARM cores actually won't work without it at all. On the earlier devices, the Videocore IV is the first one to boot, and only then do the ARM cores start running software. It has been somewhat decoupled from the system on the newest chip, so clocking it down won't probably matter much, but turning it completely off is impossible. And anyway, it won't generate much heat if it's not being used.

On the earlier devices the GPU clock actually affects CPU memory performance because the L2 cache and internal memory bus are tied to it. So up to and including 3B+/3A+, overclocking the GPU will result in slight gains in Mlucas performance.

[nomead]

https://www.tomshardware.co.uk/raspb...ews-61071.html

Already the reported heat problems are getting better...

[ldesnogu]

Originally Posted by nomead

https://www.tomshardware.co.uk/raspb...ews-61071.html

Already the reported heat problems are getting better...

And the definitive solution: https://www.cnx-software.com/2019/07...4-cooling-fan/

[ewmayer]

Originally Posted by ldesnogu

And the definitive solution: https://www.cnx-software.com/2019/07...4-cooling-fan/

Yeah, but once you get done adding all the cooling stuff, the price is nearly double the "low, low introductory offer" price. My Galaxy S7 broke-o-phone farm also needed extra cooling, but there the internal cooling system is very high-tech and one only needs to provide airflow over the case. I can cool 5 S7s with a single USB fan which costs less than your linked $20 cooler. From Nomead's tests over in the Mlucas subforum, seems a cheapish stick-on heatsink might be good enough for the Pi4, though, at least with an uncased unit.

[M344587487]

Originally Posted by ewmayer

Yeah, but once you get done adding all the cooling stuff, the price is nearly double the "low, low introductory offer" price. My Galaxy S7 broke-o-phone farm also needed extra cooling, but there the internal cooling system is very high-tech and one only needs to provide airflow over the case. I can cool 5 S7s with a single USB fan which costs less than your linked $20 cooler. From Nomead's tests over in the Mlucas subforum, seems a cheapish stick-on heatsink might be good enough for the Pi4, though, at least with an uncased unit.

A heatsink may be good enough for a single unit but a stack of them might need active cooling too. If I were to do it I'd stack 10+ pi's in a 2D grid using motherboard standoff's, with a single fan servicing them all. Put them in an enclosed tunnel and you can 3D stack them two or three layers deep if cable routing can be solved. It's kind of a moot point as the Pi is not performant enough to justify building a cluster but there may be a niche I'm unaware of. At the very least a brick of pi's would be cool.

[nomead]

Originally Posted by M344587487

A heatsink may be good enough for a single unit but a stack of them might need active cooling too. If I were to do it I'd stack 10+ pi's in a 2D grid using motherboard standoff's, with a single fan servicing them all. Put them in an enclosed tunnel and you can 3D stack them two or three layers deep if cable routing can be solved. It's kind of a moot point as the Pi is not performant enough to justify building a cluster but there may be a niche I'm unaware of. At the very least a brick of pi's would be cool.

I already have a Raspberry Pile - two stacks of five Pi3A+, with the cheap heat sinks and a 12V 120mm fan running on 5V blowing air through the stacks. Just for the fun of constructing it and fiddling with it of course, it doesn't make sense if you only look at the performance per watt, or even performance per cost. But the WiFi on the boards doesn't like to cooperate with my router so the connections are a bit flaky, and one board just refuses to communicate completely, although it's still working in every other way. I have a replacement for it... but it'll take some work to get to that one board. And instead of a bunch of microUSB power supplies, I've got two 5V 5A units that are wired to feed a stack through the GPIO pin header. The 3A+ takes about 0.9A while running Mlucas... so it is just enough.

With the improved performance on the Pi4, I might end up making another pile, but this time with wired Ethernet and netboot to avoid the hassle with SD cards. But that'll have to wait, because the Pi4 firmware binary blob is still work in progress and doesn't support netboot yet.

[hansl]

Not sure if there's anything particularly useful to do with a Gen 2 pci-e x1, but this guy has hacked into the interface:
http://mloduchowski.com/en/blog/rasp...b-pci-express/

[M344587487]

It would be nice to be able to run a graphics card with a pi but I think lack of ARM drivers makes that an insurmountable task. Maybe it's not impossible as FOSS drivers for modern AMD cards are built into the kernel and the RDNA architecture is being licensed for use with ARM cores which may help there. It would still need a very clever sod indeed to even attempt it.