Raspberry Pi 3A+ RAM Question

Hello all,

I see there are a couple topics that kind of touch on this but I can't find a definitive answer so please bear with me. I can see that @OutsourcedGuru seems to have tested this too so I hope you can see this.

Simple question - Raspberry Pi 3A+ or 3B+ for solely running Octoprint on one machine. Bear in mind its a delta so processes lots of g-code.

I would like to build the Pi into the printer (specifically behind my screen) therefore space is a premium. Also I don't need it to run anything else just Octoprint therefore I think the 3A+ should be OK? my main concern is the RAM as other posts say that the more plugins you run the more demand is needed.

Plan to run octoprint with a Pi webcam and the following plugins, PSU power control, thermal runaway, Print time genius, exclude region.

Also would like to dabble with Octolapse but not all the time.

My main concern is that the Pi cam feed would get laggy and or also cause lag when trying to start/stop/move remotely etc.

Also don't want to spend the additional money on a B+ if an A+ is suitable. The additional I/O's etc won't be used.

Any help greatly appreciated.

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I asked the same sort of question, the consensus was that RAM was the issue (the CPU being the same), OK for bare bones but multiple plugins might be a problem.

I see that PI Hut have the Pi 4B (2GB) for the same price as the Pi 3B+, so thats a no brainer.

The Pi 3A+ is 30% cheaper, 20mm shorter but slightly wider, have 50% RAM and only one USB port.

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Hello @towlerg, your posts were the ones I was referring to in my original post however I never really seen a definitive answer to wither the 3A+ was suitable for solely running octoprint.

Again you refer to 'running multiple plugins' being the option. I suppose my main question is are the 4-5 plug ins I mentioned above deemed too many for 512Mb RAM?

The 3A+ size definitely suits my printer better but I could make the 3B+ work if it is needed.

You also make a good point about the 4. However I see a lot of reports/posts/videos (YouTube) saying the 4 is no good. Prone to overheating and for Octoprint the 3B+ is better?

Again all I want is good stable camera with ability to control remotely. Nothing too fancy.

@towlerg what did you go for in the end? 3B+?

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I think I'll wiser heads to answer your remaining questions. I did indeed go for 3B+ but that was before price drop, definitely would have got a 4B (2GB), even if active cooling was deemed necessary. It never hurts to have headroom, especially when it's free. I rather suspect that a 4 doing the same work as a 3 probably dosn't get any hotter.

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Thanks @towlerg

So original question still stands, does the mentioned plug ins in OP count as too much for a 3A+?

If so then the new question is, 3B+ or 4? (same price from the PiHut and same dims)

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The one time when I thought the 3A+ was the best choice was the downstream rfc2217 project where a 3B streamed the conversation over the network to another Pi which itself was connected to the printer. The 3A+ has a single USB port and 5Ghz wifi compatibility which makes it the optimal endpoint for this.

Otherwise, I like the 3B+, the 4B these days for standard OctoPrint installation. I factor in my time. How much is my time worth if I have to run a print job twice to get one good part? It's easy for me to just buy the right Pi for the task and to not pinch pennies.

I will note that I write TFT interfaces in Kivy. Behind-the-scenes it uses the OpenGL library to render all sorts of things. When the interface involves tons of graphics and embedded webcam views then it expects lots of RAM. For this reason, I usually stick to 4B (2GB/4GB) these days for solutions.

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Thanks @OutsourcedGuru

Just to be clear then, you would recommend a 4B for Octoprint these days?

If 3B+ and 4B are the same price 4B is the choice?

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A qualified yes: note that the 4B requires a different power adapter since it's USB Type-C rather than the earlier models. If you already had the microUSB style of adapter then the 3B+ might be convenient for you.

I really love my 4Bs. I also upgrade the microSD to Class 10 and you actually notice the read/write difference. Things compile (install) much faster. You'll likely need active cooling like a fan case, however.

Short version: even though they're basically the same cost, the Class 10 microSD and fan-case will bring the price up.

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Thanks again @OutsourcedGuru.

Im planning to power it off a buckconveter and the GPIO pins so USBC isn't a problem.

For the cooling I have ordered a small fan that I intend to design into the custom housing for it too.

As for MicroSD, I will get a class 10 ordered. Any particular size? what all is stored on the SD, just the image? Or do print files save to it too?

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I suppose that all depends.

You'd think that "bigger is better". You don't have to deal with the rootfs running out of space due to logging. But know that Raspbian's log-rotation function will adjust itself to the available space; so 4X bigger space will consume much more in logspace!

If you're like me, you backup your microSD from time to time or even clone it. Imagine now having to clone 32GB IMG file(s) which just eat up space on your workstation's hard drive. Okay, so now you have to offload the zipped version of same to an external storage drive. It starts to be a hassle when you're working with larger microSD cards.

Honestly, before this I used to buy the 8GB microSD cards directly from Unirex.com in bulk. It's a good size and I can bring the card to an Ubuntu laptop, using GPartEd to shrink the second partition down in size before I then save/clone it. I then store multiple .zip files on my laptop which are about 2GB each.

And yes, your gcode files are stored on it. The biggest files are the timelapse videos you might save.

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Cheers yet again @OutsourcedGuru

You have been most helpful!!

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@mils24 My server octoprint run on a Raspberry Pi3 A+ , it works perfect and smoothly !!! I've many plugin and no issue I've reported.
An Hub usb is required if you want to use an USB webcamera(I've raspicam and an Monoprice GoPro clone ) . All is perfect, and cheaper than other sbc.
Sorry if I make any mistake , I'm Italian :slight_smile:

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Many thanks for the information @Giuseppe_La_Porta.

I have gone ahead and ordered the 4B but this is good to know and hopefully this thread is useful to someone else in the future.

Thanks again and please stay safe in the current times!

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FWIW I suggest you don't penny pinch on SD cards. I have several supposedly class 10 cards and the create from img time is wildly different. I'm using a SanDisk Extreme but there are loads of good choices eg I always buy Samsung EVO ssd's so next I'll try one of their SD cards.

Make sure the buck converter is "big" enough, appearently the 4B is power greedy.


I have 2 Creality printers, Ender3 and CR10s Pro. Originally I used two 3b+ pi's with no cameras or plugins and all was fine. I added USB cameras to both, the ender3 with less memory on it's controller board would just stop on a long print. Swapped pi's and cameras, problem stayed with the printer. Price for Pi4's dropped to $30 so I bought two and ordered two 32gb SanDisks towier mentioned above, ebay $8 each. Loaded octoprint and a good number of plugins. Both printers are running great and online response time is fantastic. Without the cameras running no fans are required but with the cameras running constantly they need cooling fans. Pi 4b' here. https://www.microcenter.com/search/search_results.aspx?Ntt=Raspberry+Pi+4+Model+B
SanDisk here.

Just my experience, Joe

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