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Raspberry Pi 3 with 2GB RAM playing the devil's advocate [result: 1GIG is enough!]

Thu Dec 29, 2016 9:18 pm

So I had the change of getting a Banana Pi M64, it has the same cpu specs at 1.2 GHz quad cortex A53 and the benchmarks seem to agree. In addition this actually has a 2Gig ram. so basically its close to what the pi3 would be with a 2gig ram module.

So, i just wanted to play devil's advocate and create real world, non-synthetic scenarios where the difference due to the ram capacity would be drastic.

So, i use this tutorial.. https://wiki.qt.io/Native_Build_of_Qt5_ ... spberry_Pi

and the .configure part was able to prove the point, the 1gig ram on the pi3 was not enough so it took 6 HOURS to complete the task as everything was being paged to swap continuously on the sd card.

the banan pi m64 however with the 2gig ram was able to complete it in 7 minutes O_o

So something like this is like a super extreme rare case that 99.99% of people running the pi3 will never encounter in their life. Again, this was just a test.

[UPDATED FOR CLARIFICATION]
just wanted to see how much advantage would we have if the pi3 had 2 gigs of ram, seem not much especially for what it would cost.

I know that the soc by design restricts the pi to 1gig and to add a 2gig module additional time and cost would be needed to redesign the soc. But i just wanted to have an apples to apples comparison and see to what extreams i need to go to overwhelm the rams capacity.

sorry to be writing in caps but people arn't getting my point.
THIS WAS JUST AN EXPERIMENT I CONDUCTED TO SEE HOW MUCH I TAKES TO OVERWHELM THE RAM ON THE PI3, 1GIG IS MORE THAN ENOUGH AND YOU COULD ALWAYS COMPILE WITH 2-3 CORES TO SAVE RAM.

VIDEO https://www.youtube.com/watch?v=6C6aeyxa8XI
Last edited by ric96 on Thu Dec 29, 2016 10:18 pm, edited 1 time in total.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 9:44 pm

You can *always* construct a scenario where whatever memory the system has isn't enough. Now if you're going to deal in the "real world", the VC4 used in all Pis to date can't address more than 1GB, so there is no way that any Pi so far could be upgraded to 2GB. To do so would require a--Guess what!--SoC redesign. Once that can of worms is opened, there are any number of things that might be considered. If I were doing it, I'd opt for *at*least* 32-bit physical addressing and would be tempted to go for 36-bit addresses, even if there were no intent for the next few years to increase the actual, installed, memory.

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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 9:49 pm

W. H. Heydt wrote:You can *always* construct a scenario where whatever memory the system has isn't enough. Now if you're going to deal in the "real world", the VC4 used in all Pis to date can't address more than 1GB, so there is no way that any Pi so far could be upgraded to 2GB. To do so would require a--Guess what!--SoC redesign. Once that can of worms is opened, there are any number of things that might be considered. If I were doing it, I'd opt for *at*least* 32-bit physical addressing and would be tempted to go for 36-bit addresses, even if there were no intent for the next few years to increase the actual, installed, memory.
I know that the soc by design restricts the pi to 1gig and to add a 2gig module additional time and cost would be needed to redesign the soc. But i just wanted to have an apples to apples comparison and see to what extreams i need to go to overwhelm the rams capacity.

I was originally planning on compiling kodi as a test as a lot more people can relate to it, but it seems that they have improved the code and kodi now compiles fine on -j4
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 9:52 pm

ric96 wrote:...real world, non-synthetic scenarios...
So something like this is like a super extreme rare case
So which is it, real world or super rare?
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 9:54 pm

Everybody knows that two gigabytes are "better" than one gigabyte, but with the current SoC its not going to happen, the current SoC is a GPU, with an ARM CPU tacked on. The GPU determines the address bus size, which determines the RAM size for the system, so for the CPU too, the max possible with the GPU's address bus is 1GB.
It was possible to replace the CPU without impairing compatibility with older models too much, but replacing the GPU is much more difficult. So without a complete GPU change more than one Gig of memory is simply impossible. Nobody even knows if Broadcom has developed a SoC that contains a similar GPU to the one in the RPI with a larger address space, and developing one costs tens of millions.

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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 9:58 pm

wildfire wrote:
ric96 wrote:...real world, non-synthetic scenarios...
So something like this is like a super extreme rare case
So which is it, real world or super rare?
Non synthetic super rear. Compiling xyz program is real world but not everyone does it every day.
Benchmarking Progrms like prime95 are usually considered synthetic as they do not serve another perpose other than benchmarking using predefined algos made to specifically stress the cpu.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 9:58 pm

RIC96 why do insist on going down this avenue, it is so much BALONEY

You are again comparing a differing hardware design :roll:
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:09 pm

ric96 wrote: Non synthetic super rear.
1) Non synthetic, I'd argue with that.

2) super rear[sic], so you admit that not many Pi users would see the benefit of your test [see 1)] but you would happily ask a charity organisation to spend hundreds of thousands if not millions of £'s for a small gain that few would benefit from.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:14 pm

wildfire wrote:
ric96 wrote: Non synthetic super rear.
1) Non synthetic, I'd argue with that.

2) super rear[sic], so you admit that not many Pi users would see the benefit of your test [see 1)] but you would happily ask a charity organisation to spend hundreds of thousands if not millions of £'s for a small gain that few would benefit from.
Never asked for the pi3 to have 2gig of ram and i am well aware that it is economically unfavourable to do so, I did an experiment to see how far i need to go to stress the ram capacity. Just proves that 1gig is more that enough.

sorry to be writing in caps but people arn't getting my point.
THIS WAS JUST AN EXPERIMENT I CONDUCTED TO SEE HOW MUCH I TAKES TO OVERWHELM THE RAM ON THE PI3, 1GIG IS MORE THAN ENOUGH AND YOU COULD ALWAYS COMPILE WITH 2-3 CORES TO SAVE RAM.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:15 pm

fruitoftheloom wrote:RIC96 why do insist on going down this avenue, it is so much BALONEY

You are again comparing a differing hardware design :roll:
i did a few bench mark to see that the performance roughly matches up, just wanted to see how much advantage would we have if the pi3 had 2 gigs of ram, seem not much especially for what it would cost.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:16 pm

mahjongg wrote:Everybody knows that two gigabytes are "better" than one gigabyte, but with the current SoC its not going to happen, the current SoC is a GPU, with an ARM CPU tacked on. The GPU determines the address bus size, which determines the RAM size for the system, so for the CPU too, the max possible with the GPU's address bus is 1GB.
It was possible to replace the CPU without impairing compatibility with older models too much, but replacing the GPU is much more difficult. So without a complete GPU change more than one Gig of memory is simply impossible. Nobody even knows if Broadcom has developed a SoC that contains a similar GPU to the one in the RPI with a larger address space, and developing one costs tens of millions.
again well aware of the fact, geez.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:18 pm

update op for clarification
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:33 pm

ric96 wrote:sorry to be writing in caps but people arn't getting my point.
Apologies Ric, I was one that didn't get your point. Now that I understand the sarcasm I am in complete agreement with you.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:37 pm

Have I stumbled on the Banananana Pi forum by accident?
Do I care about having more RAM?
Do I want a pink pony and a unicorn before I get 2GB on a future Raspberry?

These threads are such a pointless waste of time, you're not going to change RPF/RPT plans, you're not going to make a difference, so why bother. You pays your money and you makes your choice when it comes to SBC.

Some of us are old enough the remember the days before the GUI and the massive software bloat, when a 4K (yes 4096 byte) program was something larger than we'd normally see (because with base/displacement addressing on S/370 you need a new base register once you're over the twelve bit displacement that Gene Amdahl thought would be enough for most folks).

It would help the folks who are writing code today to go back to limited storage, limited disk space and all the other artificial restrictions we used to have to live with in the land of 24-bit programming. That would have stopped me having to work all night on Xmas Eve because someone wrote a program for a supermarket where they thought disk storage for a single file was limitless (until it barfed at 3,664,699,720 bytes).
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:43 pm

Dougie, I forgot to insert an emoticon in my last reply ;)
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:45 pm

Emoticons are needless GUI bloat. Stop using them. :mrgreen:
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:45 pm

DougieLawson wrote:... you're not going to make a difference, so why bother.
never wanted to, just showing the kinds of extremes one has to go before requiring to have more than a gig of ram.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:48 pm

ric96 wrote:
DougieLawson wrote:... you're not going to make a difference, so why bother.
never wanted to, just showing the kinds of extremes one has to go before requiring to have more than a gig of ram.
Stop it. The code folks write these days will expand to fill the space available because they never learned the lessons from the old fogies with beard and sandals who've been beating computers into submission for nearly forty years.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:49 pm

ric96,

Seems to me that the point is that the Raspi is not an ARM processor board/SoC.

The Raspi is a Broadcom Video Core (A GPU) which just happens to have an ARM core (or cores) grafted on.

At least that is the way I have heard the development story.

As such we are limited by the video core. Which is fine by me.

Now, having built Qt5 myself, a year ago or so, on a single core Pi 2 I know it takes forever.

Looking at the build instructions you linked to now I think there is something weird going on:

"Although the Raspberry Pi 2 provides four CPU cores, using all of them proved to be slightly unstable despite of the measures taken at the top of this page. Using three of them worked fine and led to a "satisfactory" compilation time (~12 hrs)."

Seems the build instructions try to use multiple cores to gain speed. BUT, that means multiple compilations going on at the same time. That means running out of RAM. That means going to swap on SD or wherever. That means a massive slowdown!

Perhaps, maybe, this build runs a whole lot faster when using only one core. And hence minimizing the swap hit.

Sorry but I have no Pi here just now to check this theory out on.


By the way. Did your finished Qt5 build allow running of nice fast hardware accelerated OpenGL into the frame buffer (No X Windows)? I was pretty chuffed when I saw that working on the Pi.

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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:52 pm

DougieLawson wrote:
ric96 wrote:
DougieLawson wrote:... you're not going to make a difference, so why bother.
never wanted to, just showing the kinds of extremes one has to go before requiring to have more than a gig of ram.
Stop it. The code folks write these days will expand to fill the space available because they never learned the lessons from the old fogies with beard and sandals who've been beating computers into submission for nearly forty years.
damn.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 10:55 pm

Heater wrote:ric96,

Seems to me that the point is that the Raspi is not an ARM processor board/SoC.

The Raspi is a Broadcom Video Core (A GPU) which just happens to have an ARM core (or cores) grafted on.

At least that is the way I have heard the development story.

As such we are limited by the video core. Which is fine by me.

Now, having built Qt5 myself, a year ago or so, on a single core Pi 2 I know it takes forever.

Looking at the build instructions you linked to now I think there is something weird going on:

"Although the Raspberry Pi 2 provides four CPU cores, using all of them proved to be slightly unstable despite of the measures taken at the top of this page. Using three of them worked fine and led to a "satisfactory" compilation time (~12 hrs)."

Seems the build instructions try to use multiple cores to gain speed. BUT, that means multiple compilations going on at the same time. That means running out of RAM. That means going to swap on SD or wherever. That means a massive slowdown!

Perhaps, maybe, this build runs a whole lot faster when using only one core. And hence minimizing the swap hit.

Sorry but I have no Pi here just now to check this theory out on.


By the way. Did your finished Qt5 build allow running of nice fast hardware accelerated OpenGL into the frame buffer (No X Windows)? I was pretty chuffed when I saw that working on the Pi.
I will run make sometime in the next few days, this experiment only ran .configure file. i'll run make soon at -j2 probably and let you know how it performs on X.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 11:00 pm

Don't forget to do a "make clean" first. Or perhaps delete everything and start from scratch. Jusr to be sure the same work gets done again.

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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 11:01 pm

ric96 wrote:just showing the kinds of extremes one has to go before requiring to have more than a gig of ram.
What extremes? My first computer had 4K of ram (CBM VIC 20) from there I went to 64K 128K 256K 1M 4M 8M then I went to the bigger boys the PC I am using now has 8GB, I don't see any extremes to expand it to 16 even 32GB (try fitting that into a Vic 20 or a ZX Spectrum).

So exactly what extremes do you have to go to? Pretty sure there's a few gigabits of memory up near the ISS and we can arrange a petition to get that memory to you, extreme enough?

Back on topic, right now if you need a fully functional computer with more than 1Gb of memory then the Pi is not for you.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 11:17 pm

Heater wrote:The Raspi is a Broadcom Video Core (A GPU) which just happens to have an ARM core (or cores) grafted on.
True, but also pretty much irrelevant. The ONLY thing that architecture decision really affects is the boot process in that the VPU is started first. After that it makes no difference what so ever.
Heater wrote:As such we are limited by the video core. Which is fine by me.
Only as far as the memory access goes as the caching alias is determined by the top 2 bits of the address. Pretty much everything else imposes no limitation.
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Re: Raspberry Pi 3 with 2GB RAM playing the devil's advocate

Thu Dec 29, 2016 11:31 pm

6by9,
The ONLY thing that architecture decision really affects is the boot process...
Technically I believe you are right.

However the happenstance that Eben found work at Broadcom and could co-opt the Video Core for his Raspberry Pi vision set the "genetics" of what we have now.

Had Eben found work elsewhere the Pi may never have happened, or at least been a very different machine.

Now, is it really so that an ARM core with 2, 4, 8, whatever, gigabytes of RAM can be used with the current Video Core? The way I have read things is "no".

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