Raspberry Pi Model 3 – First Impressions

I’ve gotten a new Raspberry Pi Model 3. This is a short note on my first impressions.

First off, it is finally “fast enough” that I’m not occasionally gritting my teeth at it.

The Model 2 is just slow enough at times to be a minor irritant. Yes, usable. Yes ‘enough’ computer.
But also yes, I had to wait for it sometimes.

In fairness, mostly when editing / posting articles in WordPress. That has all sorts of structural issues. Things like sending all the words of the text upstream for spell checking (whenever you type, or every 30 seconds or some such. Some browsers let you tell it when to check, FireFox is autocheck on/off only). So there’s network issues and there’s “size of text” sent issues and then it is all processed in the hideously inefficient way web pages do things ( i.e. virtual machines running generic code inside bloated host browsers inside…)

So it didn’t really surprise me that as the length of an article grew, the sloth of spell check took a bigger toll on the Pi Model 2. At some point it would reach “crossover” and I’d start having “typeahead” issues where my fingers outran the text processing and then the repeated “polling” with a block of words to spell check would start to consume enough resources that other things would start acting “less than perfect”. (In particular, mouse sensing would get a tiny bit of lag. Just enough that “marking text” would sometimes happen slightly “too late”. So I’d stop moving the mouse and let up the button then move to another place on the screen… and THEN it would react to the ‘mouse up’ and mark the text to the new location. Not an issue if you are a slow mouser… for me, I’m faster than that… Also it would tend to “tear off a tab” and make it a new browser window way too often – due to not sensing mouse up before I’d start to move the cursor off of a tab, I think.)

With the Pi 3, those issues are substantially gone. Spell check doesn’t seem to be causing any issues (I deliberately made the last articles a bit long [especially the CETA one] with quoted text, and no problems.) I still have the occasional “tab tearing” but there may be an issue with when I start the mouse move vs button up ( i.e. a PIBKAC problem…) while I think it’s ‘the same time’ maybe I’m a fraction late on mouse-up. Frankly, I’d love to just kill that feature but haven’t had the time to find out what setting (of the millions… it seems) to edit in FireFox.

The Pi 2 vs. 3, per the wiki:

https://en.wikipedia.org/wiki/Raspberry_Pi

The Raspberry Pi 2 uses a Broadcom BCM2836 SoC with a 900 MHz 32-bit quad-core ARM Cortex-A7 processor, with 256 KB shared L2 cache.

The Raspberry Pi 3 uses a Broadcom BCM2837 SoC with a 1.2 GHz 64-bit quad-core ARM Cortex-A53 processor, with 512 KB shared L2 cache.

So in addition to the 64 bit vs 32 bit, you also have a 300 Mhz speed uplift, or 300/900 = 1/3 = 33% clock upgrade and a double on the cache size (so on memory hungry apps cache misses will be much lower).

For now, the 64 bits isn’t buying much. Then again, it also isn’t costing much. I’ve just stuck in the Pi 2 Arch Linux without any recompile. As I understand it, so far, there are no custom builds using the full 64 bit ability. (That would take recompilation of the libraries, kernel, apps, etc. in a full on build). This isn’t as bad as it sounds.

As one of my instructors put it, decades back, what a 64 bit word size giveth, byte packing and unpacking taketh away. Similarly, using 64 bit instructions doubles your memory usage and doing 64 bit math much the same. (More on that and the “thumb” instructions below). The “sweet spot” for most things is about 32 bits. You have some byte packing issues, but less float and double math issues. (Doing double precision math on an 8 bit machine is just painful on the CPU) So realistically, the use of a 64 bit word and data path doesn’t buy that much more, net. It is also best if done with more than double the memory added, and the Pi 3 doesn’t add any more.

What this means is that the 64 bit processing ability is there, but unused, and unless you are doing a lot of high precision math, it isn’t going to gain much for you. If mostly doing a lot of text processing, the reduction in memory efficiency may hurt more… except the ARM chip has a way of helping on that score. The Thumb Instructions. These are smaller sized words that can be used for just that saving on space issue.

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0210c/CACBCAAE.html

1.2.2. The Thumb instruction set

The Thumb instruction set is a subset of the most commonly used 32-bit ARM instructions. Thumb instructions are each 16 bits long, and have a corresponding 32-bit ARM instruction that has the same effect on the processor model. Thumb instructions operate with the standard ARM register configuration, allowing excellent interoperability between ARM and Thumb states.

On execution, 16-bit Thumb instructions are transparently decompressed to full 32-bit ARM instructions in real time, without performance loss.

Thumb has all the advantages of a 32-bit core:

32-bit address space

32-bit registers

32-bit shifter, and Arithmetic Logic Unit (ALU)

32-bit memory transfer.

Thumb therefore offers a long branch range, powerful arithmetic operations, and a large address space.

Thumb code is typically 65% of the size of ARM code, and provides 160% of the performance of ARM code when running from a 16-bit memory system. Thumb, therefore, makes the ARM7TDMI core ideally suited to embedded applications with restricted memory bandwidth, where code density and footprint is important.

The availability of both 16-bit Thumb and 32-bit ARM instruction sets gives designers the flexibility to emphasize performance or code size on a subroutine level, according to the requirements of their applications. For example, critical loops for applications such as fast interrupts and DSP algorithms can be coded using the full ARM instruction set then linked with Thumb code.

I presume that Thumb instructions are preserved in the move to 64 bit cores. “Somewhere” I saw the value of about 8% as the total memory size increase moving to 64 bit object code on an ARM. So way better than a double, but you will still take a memory hit (albeit a small one) on making all the code 64 bit compiled. It also means some attention being paid to the details of just how you compile what (IIRC there are settings you can chose to enable Thumb instructions, or not).

Thus the lag in getting a 64 Bit OS released for the Pi 3. If it isn’t done properly and well, you could end up worse off on some measures than just running the 32 bit release.

So mostly it’s just a clock speedup and more cache that you get. For that reason I’d not been in a big hurry (besides, the Pi 2 was “good enough” almost all the time and “tolerable” the rest).

Living on it a few days

I’ve been living on it for a few days now, somewhere around 3 or maybe 4. I’m a happy camper. It doesn’t give me those “I wish it were faster” moments very often at all. (When first opening a browser with 10 tabs in it, reloading the history, I still get that, yet the CPU monitor doesn’t show it pegged so likely not a “Pi issue”. Also when saving a long posting in one tab while having hit ‘reload’ on the preview in another, I’d like more; but again that is as likely to be WordPress as the Pi… or maybe more likely).

In short, I’m quite happy with it, and the “urge” to occasionally boot up the Evo or the Chromebox is simply gone. This is a “very good thing” as now it means I’m free to try installing Linux on the HP Chromebox. Something I was a bit reticent about back when it was my “backup posting box”. What I’d go to when things got too slow on the Pi 2 with a very long posting. It has been “off” for about a month now (or maybe two) and I’ve shown I can live without it even for posting. This also means that the $35 Pi Model 3 is as usable to me as the $179 HP Chromebox. (In fairness, that was the 3 years back price… and time moves on). So despite all their differences (the Chrombox has a fairly fast Intel CPU in it and lots of memory) the speed perception is about the same, now. Yet the tendency for the Chrome “straight jacket” to bind remains. It’s the Chrome way or the highway…

As of now, on my “someday list” is to go ahead with that “Install real linux” onto the Chromebox. If I screw it up, the downside is now very small. At present, about the only thing it does better is video (and I’ve not tested video on the Pi 3 so who knows…) so ‘worst case’ is that my intention of making it a media server to the TV (CromeOS does that nicely) for Netflix gets moved onto some other box.

Anything done locally on the box seems “snappier” and just fine. Editing images in GIMP. Editing pages. I’ve not tried anything exotic yet; and I’m sure it’s not going to impress anyone for raw compute power. Also, the gamers will never be impressed (but I’m not a gamer and don’t need the newest octo-core Intel SuperDuperWattSuckium chip to make real time jet fighting happen…) For those things that I do, it is plenty and is comfortable. Since the Pi 2 was fast enough to recompile a Linux Kernel, this will be more than fast enough. That’s about the biggest one shot thing I do.

Odds & Ends

I got the heat sink kit. A finger applied to the CPU cooling fins shows them ‘mildly warm’ when at idle and ‘that seems a bit hot’ when running full tilt. I’m sure that without heatsink it would be fine, though I’d expect that at full tilt it might be pushing to the acceptable limit of CPU die temps. (That’s at ‘boiling water’ hot…) So I’d get the heatsink. It likely isn’t needed at all, but will increase die lifetime and help if you put the thing inside a challenging environment like a closed box case…I’m using one of those, but with the lid off.

Back at the wiki, per overclocking:

Pi2; 1000 MHz ARM, 500 MHz core, 500 MHz SDRAM, 2 overvolt,
Pi3; 1100 MHz ARM, 550 MHz core, 500 MHz SDRAM, 6 overvolt. In system information CPU speed will appear as 1200 MHz. When in idle speed lowers to 600 MHz.

These are “overclock” settings. I’ve not changed any of those settings on my Pi chip, so I might be running a slower clock than possible or with ‘overvolts’ lower than possible. i.e. I’ve not pushed the limits.

Oddly, or perhaps because…, I’ve not changed anything from the defaults on the Pi 2, a check on the max CPU speed (like this: sudo cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq ) gave me:

[root@ARCH_pi_64 cpufreq]# cat cpuinfo_max_freq 
1200000

so it is running at 1.2 Ghz, despite no special settings made.

But apparently I’m not stressing it much via posting anyway:

[root@ARCH_pi_64 cpufreq]# cat cpuinfo_min_freq 
600000
[root@ARCH_pi_64 cpufreq]# cat cpuinfo_cur_freq 
600000

It is also running fairly cool at the moment:

[root@ARCH_pi_64 cpufreq]# /opt/vc/bin/vcgencmd measure_temp 
temp=51.5'C

All of which is just fine with me!

(Once I figure out something reasonable to keep it busy and working, I’ll post some stats from that, too. The “at the wall” numbers.

(Oh, sidebar: Some folks may remember my ‘sporadically crashes when running 100% on 4 cores’ problem on the Pi 2. Well, it was a power supply failure. I was using one with well over 2 Amps capacity and well inside needs, but one morning it started lighting up the ‘low volts’ rainbow square even on low use. It was just marginal on volts, even when lightly loaded, and had drifted down just enough more to let that be known. My guess is that under load, it was “ok for a while”, then would have a burst of demand or a sag of supplied volts and the Pi would crash. While I’ve not gone back and stress tested the Pi 2 on another powersupply, having a component fail in a way that would have caused the issue is usually diagnostic. So that P.S. is in the garbage. It was a cheap “USB charger” cube anyway, not a device sold as a powersupply for a computer.)

From the wiki, per video:

Although the Raspberry Pi 3 does not have H.265 decoding hardware, the CPU, more powerful than its predecessors, is potentially able to decode H.265-encoded videos in software. The Open Source Media Center (OSMC) project said in February 2016:

The new BCM2837 based on 64-bit ARMv8 architecture is backwards compatible with the Raspberry Pi 2 as well as the original. While the new CPU is 64-bit, the Pi retains the original VideoCore IV GPU which has a 32-bit design. It will be a few months before work is done to establish 64-bit pointer interfacing from the kernel and userland on the ARM to the 32-bit GPU. As such, for the time being, we will be offering a single Raspberry Pi image for Raspberry Pi 2 and the new Raspberry Pi 3. Only when 64-bit support is ready, and beneficial to OSMC users, will we offer a separate image. The new quad core CPU will bring smoother GUI performance. There have also been recent improvements to H265 decoding. While not hardware accelerated on the Raspberry Pi, the new CPU will enable more H265 content to be played back on the Raspberry Pi than before.
— Raspberry Pi 3 announced with OSMC support

The Pi 3’s GPU has higher clock frequencies—300 MHz and 400 MHz for different parts—than previous versions’ 250 MHz.

Which means that someday when they actually get the code recompiled and the interfacing worked out, the Pi 3 may run video rather nicely. So once bought, it can still improve as the software catches up.

I’ll be playing around a bit with the software side of things. I’ve tried adding a couple of bits of software under ARCH vis ‘pacman -S’ and gotten odd error messages, but not tried to figure out if it is me, Arch, or the Pi 3 that’s the issue. Example?

[root@ARCH_pi_64 chiefio]# pacman -S sysstat
resolving dependencies...
looking for conflicting packages...

Packages (2) lm_sensors-3.4.0-1  sysstat-11.2.2-1

Total Download Size:   0.36 MiB
Total Installed Size:  1.82 MiB

:: Proceed with installation? [Y/n] y
:: Retrieving packages...
 lm_sensors-3.4.0-1-...   110.3 KiB   552K/s 00:00 [########################] 100%
error: failed retrieving file 'sysstat-11.2.2-1-armv7h.pkg.tar.xz' from mirror.archlinuxarm.org : The requested URL returned error: 404
warning: failed to retrieve some files
error: failed to commit transaction (unexpected error)
Errors occurred, no packages were upgraded.

[root@ARCH_pi_64 chiefio]# pacman -S kernel26-headers file base-devel abs
warning: file-5.26-1 is up to date -- reinstalling
:: There are 25 members in group base-devel:
:: Repository core
   1) autoconf  2) automake  3) binutils  4) bison  5) fakeroot  6) file
   7) findutils  8) flex  9) gawk  10) gcc  11) gettext  12) grep  13) groff
   14) gzip  15) libtool  16) m4  17) make  18) pacman  19) patch  20) pkg-config
   21) sed  22) sudo  23) texinfo  24) util-linux  25) which

Enter a selection (default=all): 
warning: autoconf-2.69-2 is up to date -- reinstalling
warning: automake-1.15-1 is up to date -- reinstalling
warning: binutils-2.26-3 is up to date -- reinstalling
warning: fakeroot-1.20.2-1 is up to date -- reinstalling
warning: skipping target: file
warning: findutils-4.6.0-1 is up to date -- reinstalling
warning: gawk-4.1.3-1 is up to date -- reinstalling
warning: gcc-5.3.0-5 is up to date -- reinstalling
warning: gettext-0.19.7-1 is up to date -- reinstalling
warning: grep-2.24-1 is up to date -- reinstalling
warning: groff-1.22.3-6 is up to date -- reinstalling
warning: gzip-1.7-1 is up to date -- reinstalling
warning: libtool-2.4.6-4 is up to date -- reinstalling
warning: m4-1.4.17-1 is up to date -- reinstalling
warning: make-4.1-3 is up to date -- reinstalling
warning: pacman-5.0.1-2.1 is up to date -- reinstalling
warning: patch-2.7.5-1 is up to date -- reinstalling
warning: pkg-config-0.29.1-1 is up to date -- reinstalling
warning: sed-4.2.2-3 is up to date -- reinstalling
warning: sudo-1.8.16-1 is up to date -- reinstalling
warning: texinfo-6.1-1 is up to date -- reinstalling
warning: util-linux-2.28-1 is up to date -- reinstalling
warning: which-2.21-1 is up to date -- reinstalling
resolving dependencies...
looking for conflicting packages...

Packages (27) abs-2.4.4-2  autoconf-2.69-2  automake-1.15-1  binutils-2.26-3
              bison-3.0.4-1  fakeroot-1.20.2-1  file-5.26-1  findutils-4.6.0-1
              flex-2.6.0-2  gawk-4.1.3-1  gcc-5.3.0-5  gettext-0.19.7-1
              grep-2.24-1  groff-1.22.3-6  gzip-1.7-1  libtool-2.4.6-4
              linux-headers-d3plug-3.4.2-2  m4-1.4.17-1  make-4.1-3
              pacman-5.0.1-2.1  patch-2.7.5-1  pkg-config-0.29.1-1  sed-4.2.2-3
              sudo-1.8.16-1  texinfo-6.1-1  util-linux-2.28-1  which-2.21-1

Total Download Size:     7.16 MiB
Total Installed Size:  200.43 MiB
Net Upgrade Size:       34.63 MiB

:: Proceed with installation? [Y/n] y
:: Retrieving packages...
 linux-headers-d3plu...     4.9 MiB  2.36M/s 00:02 [########################] 100%
 gawk-4.1.3-1-armv7h      904.3 KiB  1615K/s 00:01 [########################] 100%
error: failed retrieving file 'bison-3.0.4-1-armv7h.pkg.tar.xz' from mirror.archlinuxarm.org : The requested URL returned error: 404
warning: failed to retrieve some files
error: failed retrieving file 'sed-4.2.2-3-armv7h.pkg.tar.xz' from mirror.archlinuxarm.org : The requested URL returned error: 404
warning: failed to retrieve some files
error: failed retrieving file 'flex-2.6.0-2-armv7h.pkg.tar.xz' from mirror.archlinuxarm.org : The requested URL returned error: 404
warning: failed to retrieve some files
error: failed retrieving file 'which-2.21-1-armv7h.pkg.tar.xz' from mirror.archlinuxarm.org : The requested URL returned error: 404
warning: failed to retrieve some files
 abs-2.4.4-2-armv7h         9.7 KiB   973K/s 00:00 [########################] 100%
error: failed to commit transaction (unexpected error)
Errors occurred, no packages were upgraded.

Is there something set wrong? Is it something I didn’t do? Is Arch not ready for it’s id? Who knows. For now, I can swap the chip back to the Pi 2 for software additions. The error message implies I ought to do an update… so it is likely to be me.

As my major interest right now is trying out a different OS and doing builds from scratch, I’m more likely to go that way and not worry about these two oddities. Most folks will not be running Arch anyway (and I’m likely to ‘move on’ in a month or two) so not a big issue.

In Conclusion

I’m happy with it. It is a good “daily driver” without reservations. Sure, it could be faster, everything could be. But I find myself with “no regrets” about booting it up when I look across the room at the HP Chromebox or the Compaq EVO or even the 64 bit Antex/ ASUS box.

In short: The Raspberry Pi Model 3 is everything I need for a desktop, and would be a great learning tool for a tech oriented kid (or one you would like to be more tech oriented…) IMHO it has crossed the threshold from “nice toy, mostly can be used” into “Hey, I can live on that”.

I’m likely done with buying new kit for a while, since I no longer feel a need for more. Perhaps when I start building out a file server I’ll want SATA support or USB 3; but maybe not. Maybe when I’m doing full system builds, or maybe not. For now, picking ONE standard set of library release and kernel and build tools, then getting to work making my infrastructure kit out of the 2 x Pi Model 2’s is more important. I’ve got a perfectly fine desktop in the Pi 3, it’s the two Pi 2s that need a standard OS on them (so they can share compiles and have the right libaries matching up nicely) and need to be configured as the backend compute and file servers. Essentially, I need to build out my back room and set it up for Linux Development in a small cluster. ONLY once that is done, and ONLY if then it is found insufficient for the task, will there be anything gnawing at me about it.

The only other “bit of hardware lust” I can see is that I find the tablet fine for “on the road reading” but a PITA for posting. The Pi Model 3 is connected to a full keyboard and monitor. Not exactly Starbucks-on-the-road design. So “whenever” I go “on the road again”, my laptop envy will return. Perhaps before that I’ll get the fan fixed in the HP G6… We’ll see. For now that’s just not a need.

With that, I’m off to download some Linux images, take some test drives, maybe even try building a 64 bit kernel.

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