# Am I unreasonable to complain about USB 3 performance?

Gold Member
TL;DR Summary
I have bought a Cmos camera for astronomy. It is sold as USB3 but it will not talk to my computer reliably. Astro 'users' just say it's a known problem and are prepared to work around but I don't think that's good enough.
USB 3 was heralded as the next best thing to sliced bread and, imo, has been marketed in a not - too - honest way. It's not always as useful as the bare numbers suggest. I know the same could be said about 1GB Ethernet but Ethernet can handle all sorts of rag tag and bobtail traffic streams and STILL WORK. I guess the Engineering of Ethernet is a lot more mature and the Internet just has to work.

Astro cameras are often required to transfer image data pretty fast and the movies that are shot to get good planetary images need a good data rate. USB3 claims 5GB/s but that figure is only when things are 'just right'. I am well aware of that and my expectations are realistic.

I bought a low-end ZWO ASI290 MC camera with a 3MB sensor. Sometimes I get half decent images. With the short, supplied lead I have had 100 frames per second at times but mostly the capture programs hang up. I can accept speed restrictions but is there any excuse for hang-ups? If I have a box that produces data for transmission to another box, I would expect the comms channel to know about the channel capacity and to regulate the data transfer rate to fit. Using the camera (and others) with a USB2 lead, the frame rate goes up and down, according to cable lengths and other traffic. I can't think there's any excuse for the USB3 shortcomings.

Afaics, USB3 is very much a bolt-on system. The connectors have two data wires which give USB2 compatibility and then, in another part of the connector, two twisted pairs provide fast duplex comms. I know it's busting its little braces to achieve 5GB/s but when a system fails, it really should fail gracefully

I have a question about the "USB Traffic" control that some capture progs have. ZWO have told me to fiddle with that control and it does have some effect. It could allow some control of priorities amongst several data streams - potentially very useful but that still doesn't allow it to work unless things are just right (and I don't know what that actually means). The poor computer has frozen completely on occasions and works as soon as I pull out the camera cable. Crazy.

It's like trying to get a racehorse to pull a milk cart. And it shouldn't be like that. Are the chips just not up to requirements~?

Gold Member
While I can't contribute any solutions to your usage case, I can say that my experience with USB 3 peripherals is consistent with yours. The speed up isn't worth the increased failure rate and shoddy firmware, especially when you have multiple devices in play. I've been firmly in the ethernet camp.

A few diagnostic suggestions: have you tried to see if the capture program still hangs up using USB 3 on different ports and/or different computers (to rule out computer-specific stuff like bad drivers or w/e)? Is there any timeout option in your capture program?

Staff Emeritus
It reminds me of the history of Bluetooth, first introduced in 1989. Although we all use Bluetooth successfully now, its early history was dismal. For the first few years the implementations and experiences were so terrible, that its future was questioned.

I suspect (without direct evidence), that USB3 may be on a similar path. 10-20 years from now, you may be delighted with your USB3 devices. Woe to early adopters.

Gold Member
have you tried to see if the capture program still hangs up using USB 3 on different ports and/or different computers (to rule out computer-specific stuff like bad drivers or w/e)? Is there any timeout option in your capture program?
It's a MacBook Pro, with four Thunderbolt ports (USB3 but faster) Because there's a shortage of the mini connector cables for connecting the camera I use a hub which has various outputs including the standard USB3 size. I get the same effect on all combinations that I can make up. The hanging up business is intermittent and I can come to no serious conclusions except that it's just dodgy. I'm usually not bad at fault analysis and I can usually find a work around. I have done, actually, by forcing USB2 with a USB2 B connector with just the minimal number of pins into the camera. It's enough to be doing what I want at the moment. But it's a matter of principle and also, if I want to go for a big format Cmos camera (replacing DSLR), I will be needing quick downloads and a working USB3 will be important.
I suspect (without direct evidence), that USB3 may be on a similar path.
Probably right. But that doesn't help me tomorrow night - lol.
USB, as a concept, is ancient. I had (working) USB ports on my Power Mac in the mid 90s. At that time, manufacturers were sticking USB ports on lots of devices (digital alarm clocks and FM radios) but they didn't actually do anything, it appeared. Never any clue about firmware updating so just for show.

Specialist users such as Astrophotographers have far too humble attitudes and think it's up to them, rather than the makers, to coax the best out of their gear. As an Apple owner, I find that particularly annoying. It's odd that makers all seem to be able to produce smartphones that do all sorts of stuff reliably. I guess that some fringe gear development teams consist of two men and a dog - and it shows.

Jarvis323
I needed Thunderbolt 2 in my PC, so I got a special motherboard, a $150.00 Thunderbolt 3 adapter card, and a$50 Thunderbolt 2 to Thunderbolt 3 adapter cable. It works, but every time I restart my computer I need to take my case apart and reset the CMOS on the motherboard, then I need to go into bios again and renable Thunderbolt to use it again. I duel boot Linux and Windows, and only use Windows when I need the Thunderbolt device, so I have to go through this every time I use it.

sophiecentaur
Gold Member
It's a MacBook Pro, with four Thunderbolt ports (USB3 but faster) Because there's a shortage of the mini connector cables for connecting the camera I use a hub which has various outputs including the standard USB3 size. I get the same effect on all combinations that I can make up. The hanging up business is intermittent and I can come to no serious conclusions except that it's just dodgy. I'm usually not bad at fault analysis and I can usually find a work around. I have done, actually, by forcing USB2 with a USB2 B connector with just the minimal number of pins into the camera. It's enough to be doing what I want at the moment. But it's a matter of principle and also, if I want to go for a big format Cmos camera (replacing DSLR), I will be needing quick downloads and a working USB3 will be important.

I hear ya. Glad to know the USB 2 is working out. On principle, USB 3 has never been an advantage for me personally in the lab because I've only worked on atomic experiments where images were collected only a couple times a second at best. One bad shot due to interfacing shennanigans in an automated 3 hour data set made all the speed benefits moot. That's just been my philosophy on it, but I get it's different when you're collecting images in real time. The real shame is that scientific camera manufacturers don't offer a 10 gigabit ethernet option as an alternative to USB 3. I get that 10 gigabit ethernet is uncommon and therefore expensive, it's just a shame. Call me crazy but I'd rather lug around a PC with a network card than have to babysit connections all day

sophiecentaur
Gold Member
It's a MacBook Pro, with four Thunderbolt ports (USB3 but faster) Because there's a shortage of the mini connector cables for connecting the camera I use a hub which has various outputs including the standard USB3 size.

We (unfortunately) have to use quite a few USB instruments in my lab. To be fair, as long you are using say 2-3 instruments it works quite well; but once you've added a few more than that USB becomes unreliable even if there are no requirements for speed. These days, we are trying to only buy instruments with Ethernet connections.

That said, one thing we have noticed is that the quality of USB hubs can make a dramatic difference if you need high speeds. Cheap USB hubs tend to work well if you only want to connect some dongles and a headset, but that is about it. The DC supplies in regular hubs also tend to be very bad which can be an issue for USB powered electronics.
In the lab we therefore sometimes use "lab grade" USB hubs, the problem is they are expensive (~$200) and so far USB 2.0 only. I understand that this might not apply to you if you are using an "official" Mac hub to add ports to your computer, but it is worth keeping in mind that hubs can be critical components. Twigg Science Advisor Gold Member In the lab we therefore sometimes use "lab grade" USB hubs, the problem is they are expensive (~$200) and so far USB 2.0 only.
HAHA. The family could go without food for a few days, I guess. Perhaps the manufacturers are avoiding stepping into the mire of USB3 until they can rely on no customer complaints.

There are probably as many solutions to the problem of connecting astro gear as there are astrophotographers. If I spent several hundred £££, I could buy a ZWO hub that claims to do all that's needed but they are reluctant to be very open about simple things like my single camera so would it really do the job! It's a bit demanding to provide a fast download of images and also guiding information from another camera - but much less of a demand than you have in your lab.

On the subject of guiding - I keep reading posts from people who have difficulties. Guiding works by providing small adjustments to the two telescope axes, to keep the 'guide star'. The guiding signal goes to the mount by a separate route, direct from the guide camera. The mount gets tracking data from the computer / handset which, in the old days was all that was available (used to be clockwork or a friend with good concentration). I just heard the word "nightmare" on the radio in the background. Appropriate, I think.

Gold Member
I get that 10 gigabit ethernet is uncommon and therefore expensive,
Most amateur astronomers are truing to use WiFi!
I did wonder about Ethernet and an optical link to the house but the fibre cable would cost as much as all my kit added together, I think. And, unlike Football, Astrophotography is not even a matter of life and death.

Staff Emeritus
I am not sure what your complain is. Is it with USB3 as a protocol? Is it that USB3 is slower than advertised? Is it that your (your words) "low end" camera doesn't implement it well?

If your answer is "slower than advertised", yes, it is. 5 Gbps is signaling speed. Because it uses 10b/8b encoding, you only get a maximum of 4 Gbps out of the gate. Adding overhead reduces this - a 10-15% overhead means you'll max out around 3.4-3.6 Gbps for payload transfer.

I should point out that Wifi does the same thing, only worse. My router claims "1900 Mbps" but I get reliable transfers at 40 +/- 2 MB/s: 17% of what is advertised.

Gold Member
I am not sure what your complain is.
Basically I don't expect a device that I connect up should freeze the apps and sometimes the computer. Would anyone find that acceptable?

Gold Member
Basically I don't expect a device that I connect up should freeze the apps and sometimes the computer. Would anyone find that acceptable?
That sound more like a driver issue than something specifically about the USB protocol. The same thing can happen with any interface , it is just more obvious with USB since the driver is automatically "triggered" when you connect a device.

Staff Emeritus
Basically I don't expect a device that I connect up should freeze the apps and sometimes the computer. Would anyone find that acceptable?

Sure, but why blame USB? Why not blame, I dunno, blue connectors?

You bought something cheap ("low-end") and discovered it didn't work very well. I've had that experience myself many times.

Gold Member
That sound more like a driver issue than something specifically about the USB protocol.
You may be right but I would expect the manufacturer to be aware of the problem. Also, problems are widely reported, wherever the cause.
It's not up to a customer to fault find.

Gold Member
You bought something cheap ("low-end")
You seem to be a bit defensive about ZWO. It was not very expensive because it has a relatively small image sensor. It wasn't just £25 ;-) The comms circuits wouldn't necessarily be too different.

If they can't rely on usb3 performance then why offer it? Have you looked on forums about the problems with usb3? I am definitely not alone in my problems.

It functions fine on usb2 - the images are very fair and the frame rate (image size dependent) is consistent with usb2 capacity. The "blue" usb2 connector works and several others do too. Two usb3 connecting leads from ZWO show the same faults. I'd be more than willing to try another AS!290 camera if ZWO suggest that. We shall see.

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Gold Member
Most amateur astronomers are truing to use WiFi!
And I thought I was a glutton for punishment

Most amateur astronomers are truing to use WiFi!
I did wonder about Ethernet and an optical link to the house but the fibre cable would cost as much as all my kit added together, I think. And, unlike Football, Astrophotography is not even a matter of life and death.
One trick I've found with networking parts is to buy them second hand on ebay. I can't explain it, but you can find stuff for an order of magnitude less cost. Clearance sales for corporations, I guess? But out of curiosity why go the fiber route when there's cat6 for a tenth of the cost per foot?

Edit: IIRC the raspberry pi 4 has a 10 gigabit ethernet port, and that's what I use for a 10 gigabit router. 10 gigabit network switches are something you can find on ebay for much less.

You bought something cheap ("low-end") and discovered it didn't work very well.
I hear you on this, but I think there is some truth to what sophiecentaur is saying. You can buy a cheap peripheral with USB 2.0 or 1000/100/10 ethernet interfacing, and you'd never have to worry about the quality of the drivers no matter how sketchy the price is. Buy a cheap USB 3.0 peripheral and it's like opening pandora's box. The worst part for me is that buying a part with the "USB 3.0" standard doesn't guarantee a level of performance, as it does with the older interfaces. It'd be nice if there was something like, FTDI certifying devices that aren't crud but I know that's not financially viable.

Gold Member
Buy a cheap USB 3.0 peripheral and it's like opening pandora's box.
I wouldn't mind if the ZWO camera was, in fact cheap. ZWO seem to be aiming for being accepted as being leaders in this equipment. As a usb2 box it's well up to what's needed.

I was trying to avoid the extra complication of a computer at the scope mount to do it all. I haven't used raspberry pi. Perhaps that would be the way to go. But it's not the issue with my question. You have actually answered my question, thanks. It seems there's an issue where there shouldn't be with usb3.

I am still in conversation with ZWO so they may yet be helpful.

Gold Member
@Twigg I will take your advice, thanks, and look at a better usb3 hub than the basic ANKER one I happened to have already. Something with a mini connector, for a start.
I've used a similar purchase strategy by checking on full prices with credible suppliers. eBay has loads of stuff - I just looked.

Staff Emeritus
You seem to be a bit defensive about ZWO.

Never heard of them, much less used them. My point is that an el-cheapo implementation of a particular standard doesn't necessarily reflect on this standard. Further, I don't understand why calling them low-end is defending them.

As far as USB3, I use it regularly with data transfer rates between 1 and 2 Gbps with no problems. As far as USB certification, do you think you could buy a USB3 flash drive for \$2.49 if they had to be certified?

russ_watters
Jarvis323
I've learned over time to be weary of devices using new connection types, even with high end devices. Sometimes they work, but only in very specific situations depending on your computer hardware, OS version, etc. It can be caused by the developers of the device driver, or by the developers of the OS, or the developers of the firmware on your motherboard. It can take years before things become reliable in general.

That said, one thing we have noticed is that the quality of USB hubs can make a dramatic difference if you need high speeds.

Absolutely! I use a Plugable USB-C dock and it's quality...but expensive. It connects my Dell laptop to the Ethernet LAN at GB speed, drives two HD monitors (and can support a 4K one), plus peripherals such as mouse and keyboard, and it powers the laptop.

So, it's not that USB 3.0 can't support high-throughput devices.

But, as The Verge co-founder Nilay Patel often complains about, USB is confusing and that can lead to poor performing devices...and cables. I had a dodgy USB-C cable and it drove me crazy until I swapped it over. I doubt that's @sophiecentaur's problem, but as with anything high-performance, your results will vary with vendor and when it comes to 'inexpensive' products, they may not adhere to the highest specifications possible.

Gold Member
Never heard of them, much less used them. My point is that an el-cheapo implementation of a particular standard doesn't necessarily reflect on this standard. Further, I don't understand why calling them low-end is defending them.
So have you actually any experience of the sort of camera that's giving me problems or how a camera may be different from a storage device? I have no problems getting high data rates between my MBP and two external hard drives but that's not the same thing, is it? But it should be.

I didn't describe the camera as "el-cheapo". I have a friend who bought himself a Porsch - from the low end of the range. Did that make it "el cheapo"?

I was after some useful information to help solve my problem and there has been some useful information on the thread.
So, it's not that USB 3.0 can't support high-throughput devices.

But, as The Verge co-founder Nilay Patel often complains about, USB is confusing and that can lead to poor performing devices...and cables.
So I should not be surprised too much when USB3 let's me down? I think I am fully justified in complaining when it does, though. Things that don't do what it says on the tin (and which are not just costing me pennies) should always provoke complaints up the chain.
I think I'll keep nagging at them and possibly get my money back.

Gold Member
devices using new connection types,
USB goes back decades. Not as far as Ethernet, agreed.

Jarvis323
USB goes back decades. Not as far as Ethernet, agreed.
Yeah, but from 2 to 3 was a big change. The computer hardware market is always driven by improvements like these, so the manufacturers want to sell the new stuff with the higher speed as fast as possible, and that often leads to them releasing stuff before it's been tested and debugged adequately. The first customers then act as the testers and they just fix things as they're reported. They should be paying us.

And then they only have so many resources dedicated to fixing the bugs, so they prioritize. Often they only fix the ones affecting the bulk of the customers, eventually. And bugs affecting the more rare configurations might never get fixed.

Gold Member
I want to add an addendum to my post from earlier. I'm familiar with those ANKER hubs and I would not be suprised if your hangup problem was solved by upgrading the hub, as others have said. When I said that in my experience in atomic physics research, USB 3.0 was not worth it, we used hubs recommended by our IT pros because we were counting on them to function. That level of reliability would probably (?) be adequate for astrophotography. Where it hurt us was when a USB interfacing hickup caused an automated dataset to fail, and USB devices would just cease to be connected mid operation. It happened on the order of once a week, and we ran these systems hard 12+ hours a day. For the average user, those are great performance statistics. For hardcore data collection, it sucks. (It seems to me astrophotography falls somewhere in between.) These kinds of problems don't happen with ethernet because, in sophiecentaur's words, the internet has to work, period. I have never ever heard of a tcp/ip network failing at the ethernet layer. It just doesn't happen. That's what I mean when I say USB 3.0 is unreliable in my point of view. It has nothing to do with data transfer speed and everything to do with the invisible hand of the market.

I think I am fully justified in complaining when it does, though.

I agree, though the devil is in the detail of the device. And sorry, I've not trawled through all the comments to extract exactly every problem solving step you've tried, @sophiecentaur, so:
1. Does your camera include USB 2.0? It shouldn't matter but it could be flopping between USB protocols?
2. You note the hub has "USB3 size" connector, but USB 3 does not dictate the connector, that's a separate standard. Are you referring to the USB-B connector, that's the most common one. USB-C is the newer one that is not directional in terms of plugging it in.
3. If the hub is USB-B (the common, directional connector) then it's likely unable to connect at the higher USB 3 speeds.
4. If you've plugged the camera directly into your MacBook, then the hub is not the problem.
5. Have you tried different cables? Inexpensive cables frequently cause issues as they are more prone to break internally.
6. I'm not sure what the situation is with retail shops being open, but is there somewhere you can take your MacBook and your camera and have someone else diagnose it with their kit to compare directly to your kit?
7. Do you have a recent Windows 10 machine that you can try the camera with directly? And then via the hub?
8. Has the vendor confirmed that their product is compatible with macOS? Some vendors do not bother writing drivers or validating against Apple operating systems.
Apart from all that, USB 3 has been around for many years, with multiple versions and generations within the versions offering different capabilities - mostly higher speeds, all called SuperSpeed something, as if that's not confusing! And of course, they've changed the plug along the way and most people assume the USB-C plug means USB 3 but it doesn't have to.

The USB Implementers Forum (USB-IF) is responsible for all these variants and they tried to harmonize the landscape last year but that's mostly marketing, it doesn't change whatever version / generation device makers have adopted.

I have never ever heard of a tcp/ip network failing at the ethernet layer

It used to...and it still can...but stringent categories of cabling have markedly increased reliability over the years. And TCP/IP has recovery built into the protocol. UDP channels don't, and that's when you'd find out your Cat 5 cable was poorly installed because data would be lost!

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Twigg
glappkaeft
Absolutely! I use a Plugable USB-C dock and it's quality...but expensive. It connects my Dell laptop to the Ethernet LAN at GB speed, drives two HD monitors (and can support a 4K one), plus peripherals such as mouse and keyboard, and it powers the laptop.

So, it's not that USB 3.0 can't support high-throughput devices.

While you can run USB 3.0 using a USB-C cable that dock is a Thunderbolt-3 device. A completely different protocol that is many times faster than USB 3.0.

While you can run USB 3.0 using a USB-C cable that dock is a Thunderbolt-3 device. A completely different protocol that is many times faster than USB 3.0.

Oops. Thanks for pointing that out, @glappkaeft, and I'm embarrassed because I had noted that the USB-C connector does not have to run the USB protocol...and entirely missed that applies to my Dell as it's a Thunderbolt port 🤦‍♂️

Gold Member
If anyone is interested in digging/troubleshooting more deeply, there is a wealth of documentation and test tools (even for testing hubs) at:
https://www.usb.org/documents

The tools require Windows 7 or above.

In my experience with USB 2, hubs are the most likely problem and bad cables next. "Bad" cables are not limited to damaged, there are some really, really low quality cables out there. (About the only thing those bad cables are good for is hanging yourself strangling the supplier when 'Nothing Works.')

Cheers,
Tom

EDIT: p.s. A limited search for USB 3 shows cable length of 3 to 5 meters. Beyond that you need an active cable.

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Twigg and russ_watters
Gold Member
Any reason one might blame the data collection software for spurious hangs etc? Having written some I see more than enough threading difficulties, buffering and race conditions to go around. I'm certain with my coding skills I could get such to hang using USB2.

Kenwstr
Just a thought:

I've had a lot of reliability issues with USB3 as well. While there can be processing issues. It seem to me to often relate to the electrical connection of the USB3 plugs themselves. A quick spray with Deoxit F5 often does the trick. I suspect there may be small particles getting into the plugs making for poor and intermittent electrical contact. The contact area is smaller with USB3 after all. The F5 product is a quality contact cleaner lub and conditioner that improves and protects electrical contact and performance of mechanical components like pots, faders, trimmers, switches and plugs etc. It's expensive but with over 30 years messing about with audio and electronics, it's safest and most reliable one I have found. It's amazing how many computing hardware issues just come down to electrical continuity, disappearing files on drives etc interrupted registry/index update for example. I've even had missing files reappear after restoring connections in this way. As mentioned by others, alternate high capacity connection type wouldn't hurt.

shjacks45
Summary:: I have bought a Cmos camera for astronomy. It is sold as USB3 but it will not talk to my computer reliably. Astro 'users' just say it's a known problem and are prepared to work around but I don't think that's good enough.

USB 3 was heralded as the next best thing to sliced bread and, imo, has been marketed in a not - too - honest way. It's not always as useful as the bare numbers suggest. I know the same could be said about 1GB Ethernet but Ethernet can handle all sorts of rag tag and bobtail traffic streams and STILL WORK. I guess the Engineering of Ethernet is a lot more mature and the Internet just has to work.

Astro cameras are often required to transfer image data pretty fast and the movies that are shot to get good planetary images need a good data rate. USB3 claims 5GB/s but that figure is only when things are 'just right'. I am well aware of that and my expectations are realistic.

I bought a low-end ZWO ASI290 MC camera with a 3MB sensor. Sometimes I get half decent images. With the short, supplied lead I have had 100 frames per second at times but mostly the capture programs hang up. I can accept speed restrictions but is there any excuse for hang-ups? If I have a box that produces data for transmission to another box, I would expect the comms channel to know about the channel capacity and to regulate the data transfer rate to fit. Using the camera (and others) with a USB2 lead, the frame rate goes up and down, according to cable lengths and other traffic. I can't think there's any excuse for the USB3 shortcomings.

Afaics, USB3 is very much a bolt-on system. The connectors have two data wires which give USB2 compatibility and then, in another part of the connector, two twisted pairs provide fast duplex comms. I know it's busting its little braces to achieve 5GB/s but when a system fails, it really should fail gracefully

I have a question about the "USB Traffic" control that some capture progs have. ZWO have told me to fiddle with that control and it does have some effect. It could allow some control of priorities amongst several data streams - potentially very useful but that still doesn't allow it to work unless things are just right (and I don't know what that actually means). The poor computer has frozen completely on occasions and works as soon as I pull out the camera cable. Crazy.

It's like trying to get a racehorse to pull a milk cart. And it shouldn't be like that. Are the chips just not up to requirements~?
Actually you are right in assuming that vendors claiming USB 3.0 compatibility under the umbrella of USB 2.0 subset of USB 3.0 operation. Or their device is USB 3.0 if it uses more than USB 2.0 0.5 Amp power limit. When you see wifi, ethernet, fiber, or usb: claims are "Up to" 6 Gbits per second is actually a guarantee that that is max speed possible. If you know a little physics, you will recognize the term "bit jitter". It is the fact in the physical transmission of data, that higher frequencies (rapid data changes) travel more slowly along a cable than slower frequencies. All fast data transmission is serial since the bit jitter issue affect sync of parallel data transmission worse. Any deviation from straight or proximity to other conductors slow transmission speed and muddle those data bits. Equivalent speed copper ethernet has similar distance limitations. Optical fiber allows long distance transmission of high speed data but alas the maker of your sensor array didn't consider that. USB-over-Wifi does bypass USB cable length issues. USB 1.1 max was 18 ft., USB 2.0 high speed 6 ft, USB High Speed (480 Mbits/sec) max length 18 inches. For computers built with internal USB 3.0 DVD or hard drive, data rate (burst data; physical devices don't read data that fast) on USB 3 is faster than SATA or PCIe.
CRITICAL to speed is USB 2 uses polling (cpu wastes its time checking port) vs USB 3 interrupt mode (optional) which automates data transfer signaling when data is freshly available. The faster mode is not a given. Pardon my predjudice, but the first Rasperry Pi had a "synthetic"(software) USB port and even the Pi 3 had underwhelming tranfer rate with external devices, HOWEVER addon USB/network hats for the Pi (with real usb controller chips) will boost the Pi's USB speed considerably.

Gold Member
I didn't read all replies here so sorry if duplicating. But I would not diagnose any performance issue, including IO devices, without asking about RAM and cache capacity of the system, and whether SSD or HDD. This is because of caching and swapping to disk. Sometimes simply beefing up RAM can make a difference. Surprisingly often in my experience.

Paul Colby
shjacks45
I didn't read all replies here so sorry if duplicating. But I would not diagnose any performance issue, including IO devices, without asking about RAM and cache capacity of the system, and whether SSD or HDD. This is because of caching and swapping to disk. Sometimes simply beefing up RAM can make a difference. Surprisingly often in my experience.
You understand that SATA, m.2, USB, PCIe, are all peak burst transfer rate and the speed of the speed of the media is typically orders of magnitude slower. Like gamers getting "primo" video card that's using 4x of their 16x PCIe card slot. Speed? Depends on storage device and your controllers. Generally SATA gets request from program, moves the data, then tell cpu its done. USB 2.0 (allowable in usb3) requires your CPU to check for every data byte (polling) which is slower than the transfer rate even on a fast computer doing nothing else. True USB 3 allows true device to memory data movement with minimal cpu intervention. The m.2 interface is a modified PCIe 1x channel. The PCIe 1x interface found on USB3, ESATA, Ethernet, RAID controller, is slower than the interface standard.
Note on SSDs. How come the SSD makers say the mean time before failure is 150 years, but the memory chip makers say you data only good for 10 years max? However SSDs, the flash chips, have a relatively low maximum writes compared to magnetic and the flash controller uses wear leveling to make that less catastrophic. Flash memory has transient bad bits (not an issue with stored images as artifacts aren't noticed) and requires error correction bits to prevent data errors. A digression to point out that using SSD as swap drive is a bad idea. Think Microsoft "Ready Boost".

Paul Colby
Mentor
Astro cameras are often required to transfer image data pretty fast and the movies that are shot to get good planetary images need a good data rate. USB3 claims 5GB/s but that figure is only when things are 'just right'. I am well aware of that and my expectations are realistic.

I bought a low-end ZWO ASI290 MC camera with a 3MB sensor. Sometimes I get half decent images. With the short, supplied lead I have had 100 frames per second at times but mostly the capture programs hang up. I can accept speed restrictions but is there any excuse for hang-ups? If I have a box that produces data for transmission to another box, I would expect the comms channel to know about the channel capacity and to regulate the data transfer rate to fit. Using the camera (and others) with a USB2 lead, the frame rate goes up and down, according to cable lengths and other traffic. I can't think there's any excuse for the USB3 shortcomings.
I am not sure what your complain is. Is it with USB3 as a protocol? Is it that USB3 is slower than advertised? Is it that your (your words) "low end" camera doesn't implement it well?
[sigh] I have a ZWO ASI1600 that I bough largely for the 2017 solar eclipse. I don't advertise it, but I didn't get much out of it -- almost all of the finished photos I got were essentially from my back-up rig. In addition to being hard to use (weird settings, thin documentation, no native software), it also had an un-documented bug that ruined a significant fraction of the images, that I didn't get rectified until months later when tech support emailed me a firmware update that fixed it.

That saga's not over yet. A year and a half ago the mount for my scope loosened I guess due to the temperature drop, and pile-drove the camera into my deck. The USB cable was shredded and shoved the USB port up into the camera body. I waited more than a year to try and fix it and it turns out that after removing a loose body and straightening-out the USB port (and replacing the *USB3 cable), it seems to work. But I haven't tried yet to see if it is really usable...
sophiecentaur said:
I have a question about the "USB Traffic" control that some capture progs have. ZWO have told me to fiddle with that control and it does have some effect. It could allow some control of priorities amongst several data streams - potentially very useful but that still doesn't allow it to work unless things are just right (and I don't know what that actually means). The poor computer has frozen completely on occasions and works as soon as I pull out the camera cable. Crazy.
So I just bought a new camera for planetary imaging, a QHY290. It's another Chinese manufacturer, with a lot of the same shortcomings. But if it is good enough for Chris Go, it should be good enough for me. Nope. The first night with it was yesterday; balky connections, and when it did work, I was getting like 4 fps. It's advertised as capable of 200+fps at 1920x1080.

Whelp, after a little troubleshooting I found that the unreasonably short, included USB3 cable was the culprit. Fortunately I had *a spare USB3 cable lying-around to try. Now it gets a spinning-hard drive-limited 58fps, transferring data at 235 MB/sec.

Anyway, USB traffic: Near as I can tell it is some sort of throttling function, reducing the framerate and transfer rate to avoid overloading the bus.
https://astrojolo.com/gears/cmos-setting-challenge/

The manufacturers seem to be comparing notes, because it is a rare feature that exists on both my ZWO and QHY cameras -- but with opposite settings.