There's no reason to replace USB A on most desktops since it would break 20+ years of backwards compatibility without any real benefit. Maybe 1 or 2 would be useful.
this post was submitted on 19 Nov 2023
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So, much as I hate to admit it, the real reason for this is bandwidth. Lets look at the best case scenario without dipping our toes into server grade hardware. AMD CPUs tend to have more I/O bandwidth allocated than Intel, so we'll take the top of the line desktop AMD CPU as of right now, the Ryzen 9 7950X (technically the X3D version is the actual top of the line, but that makes certain tradeoffs and for our purposes in this discussion both chips are identical).
On paper, the 7950X has 24 PCIe 5.0 lanes, and 4 on board USB 3.2 ports on its built in USB controller. So already we could have a maximum of 4 type-C ports if we had no type-A ports, however in practice most manufacturers opt to split the difference and go with 1 or 2 type-C ports and the remaining 2 or 3 ports as type-A. You can have more USB ports of course, but you need to then include a USB controller on your motherboards chipset, and that in turn needs to be wired into the PCIe bus which means taking up PCIe lanes, so lets take a look at the situation over there.
We start with 24 PCIe lanes, but immediately we're going to be sacrificing 16 of those for the GPU, so really we have 8 PCIe lanes. Further, most systems now use NVMe M.2 drives, and NVMe uses up to 4 PCIe lanes at its highest supported speed. So we're now down to 4 PCIe lanes, and this is without any extra PCIe cards or a second NVMe drive.
So, now you need to plug a USB controller into your PCIe bus. USB 3.2 spec defines the highest supported bandwidth as 10 Gbps. PCIe 5.0 defines the maximum bandwidth of a single PCIe lane as a bit over 31 Gbps. So the good news is, you can successfully drive up to 3 USB 3.2 ports off a single PCIe 5.0 lane. In practice though USB controllers are always designed with even numbers of ports, typically 2 or 4. In the case of 4, one lane isn't going to cut it, you'll need at least 2 PCIe lanes.
I think you can see at this point why manufacturers aren't in a huge rush to slap a ton of USB type-c connectors on their motherboards. With a modern desktop there's already a ton of devices competing for limited CPU I/O bandwidth. Even without an extra USB controller added in it's already entirely feasible to come dangerously close to completely saturating all available bandwidth.
I think power delivery is a concern too. If a motherboard had 4 USB-C ports on it, you know someone would try to plug in 4 USB-C monitors at 100W (20V/5A) each, so 400W going across your IO bus. At that point if your motherboard doesn't just burn out, and you have a big enough power supply to provide it, you're still going to have a serious heat problem.
Yeah I recently started using a motherboard that has a 6-pin GPU style header for powering the USB-C ports. It limits power delivery capacity if you don't plug the connector in, but if you do it supports 100W ports.
100W on each port or 100W total output for all 6 ports? I seriously doubt your power supply will deliver 600W on one peripheral cable.
Don't support 100W power delivery on all ports then.
I think it's easy to say this, but harder to actually do in practice. There's a color code system for USB-A, but a lot of manufacturers didn't follow it reliably, and most users don't know what the differences are anyway (I'd certainly have to look up what Yellow and Red are specifically for). You'd have the same problem with trying to mark USB-C ports, and without some easily identifiable marking most users will just expect that a USB-C port is a USB-C port.
Thank you for the detailed and enlightening explanation!
They don’t all have to be high speed. For example, we already see a distinction in USB-A based on things like power and data speed. I don’t see why anyone would be surprised at a similar arrangement for USB-C. Let me have my low speed keyboard and mouse ports, my low power watch charging port
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Not al usb c ports have to gen 2.2, just a few 3.0 ports would be neat.
Nah, they usually advertise one USB-C port with full speed and that is the only one who gets it, even if it has 2, 3 or even 4x.
Btw, the DeskMini is the only full-spec PC i know of, which doesn't use additional chipsets for I/O. There may be a few more boards like this, dunno, but additional I/O chipsets are incredibly common.
Isn't this glossing over that (when allocating 16 PCIe lanes to a GPU as per your example), most of the remaining I/O connectivity comes from the chipset, not directly from the CPU itself?
There'll still be bandwidth limitations, of course, as you'll only be able to max out the bandwidth of the link (which in this case is 4x PCIe 4.0 lanes), but this implies that it's not only okay but normal to implement designs that don't support maximum theoretical bandwidth being used by all available ports and so we don't need to allocate PCIe lanes <-> USB ports as stringently as your example calculations require.
Note to other readers (I assume OP already knows): PCIe lane bandwidth doubles/halves when going up/down one generation respectively. So 4x PCIe 4.0 lanes are equivalent in maximum bandwidth to 2x PCIe 5.0 lanes, or 8x PCIe 3.0 lanes.
edit: clarified what I meant about the 16 "GPU-assigned" lanes.
Typically no, the top two PCIE x16 slots are normally directly to the CPU, though when both are plugged in they will drop down to both being x8 connectivity.
Any PCIE x4 or X1 are off the chipset, as well as some IO, and any third or fourth x16 slots.
So yes, motherboards typically do implement more IO connectivity than can be used simultaneously, though they will try to avoid disabling USB ports or dropping their speed since regular customers will not understand why.
Typically no, the top two PCIE x16 slots are normally directly to the CPU, though when both are plugged in they will drop down to both being x8 connectivity.
Any PCIE x4 or X1 are off the chipset, as well as some IO, and any third or fourth x16 slots.
I think the relevant part of my original comment might've been misunderstood -- I'll edit to clarify that but I'm already aware that the 16 "GPU-assigned" lanes are coming directly from the CPU (including when doing 2x8, if the board is designed in this way -- the GPU-assigned lanes aren't what I'm getting at here).
So yes, motherboards typically do implement more IO connectivity than can be used simultaneously, though they will try to avoid disabling USB ports or dropping their speed since regular customers will not understand why.
This doesn't really address what I was getting at though. The OP's point was basically "the reason there isn't more USB is because there's not enough bandwidth - here are the numbers". The missing bandwidth they're mentioning is correct, but the reality is that we already design boards with more ports than bandwidth - hence why it doesn't seem like a great answer despite being a helpful addition to the discussion.
Am I throwing away all my mice, keyboards, DAC, digital pens, and other peripherals just so I can have a connector with more bandwidth than I'll ever need? Nah.
Am I buying them or adapters all over again just so I can be compatible with a new universal standard that I don't need? Double nah.
KVM switches, or breakout hubs that these devices plug into, then a single USB c device goes to the computer is the most logical avenue for a migration. But this will take a long time. Most people don't even have that kind of luxury.
On the other side of that, I’m already stuck throwing away all my Lightning cables and chargers, and ideally want to change only once. Why is it so hard to jump right to C for everything?
What on earth would possess folks to replace their often expensive existing peripherals for no benefit? To totally get rid of USB-A a person will either be out a bunch of money or be stuck with having to keep track of adapters for all their devices they can currently just plug in. An industry move to do so would necessitate the creation of a huge amount of e-waste and would net everyone else precisely nothing.
USB-C is great for mobile devices as it's small, relatively robust, easier to connect, and does pretty much everything from power deliver to video to connecting any device imaginable. Desktops (and even laptops really) don't need to place such a premium on port size. Laptops and other mobile devices standardizing on USB-C for power is great. We can charge all our devices from the same charger. Fantastic!
Making 20+ years of working equipment harder to use and forcing billions of people to buy stuff they don't need (and that many can't afford) would be wild.
Expect to continue seeing USB-A for a long, long time. No need to replace anything with a USB-C version until it breaks (and maybe not even then).
sure, but some people are already in a position where they already have only USB-C (me). I have adapters for the USB-A ports and it sucks. Just let me choose to get rid of the old shit that I don't need please
But we're not at the point of debating whether users should replace all of their devices. If motherboards with a single USB-C are so common, we're actually at a place where we're expecting users to buy all their new peripherals to be USB-A as well.
I agree most motherboards should at least come with 2 or 4 USB-C ports.
That being said, people upgrading all their peripherals happens significantly less often than the PC upgrade itself, and 90% of my current setup relies on USB type A, so if a motherboard (specially mATX) needs to decide what ports to fit into limited space, I'd prioritize USB A for sure.
Yeah, I've got mostly USB-A peripherals, and the USB-C ones are using a USB-A to C cable anyway. What I'd actually want is graphics cards with the same Thunderbolt type ports that laptops have, so the USB stuff can be pushed through the same cable to your monitor.
Because there is no reason to have more than 1 or 2 since almost everything uses a type A connector.
Most desktop peripherals are still USB-A. For low-power, low-data things like keyboards and mice, what would be the point of USB-C? It would increase the cost of the product but provide no real benefit to the user.
Also, if you had a new desktop motherboard with say 6 USB-C ports, would you expect all of them to be capable of delivering 20V at 5A so they can be used to drive USB-C monitors &etc? Because that's a lot of power to be running across your motherboard, even if you have a power supply that can handle it. You'll need a separate cooler just for the USB-C bus controller, and pray that nothing ever goes wrong with power delivery because it will probably fry the whole board.
How the heck is USB-A a legacy port and what would I do with 11 USB-C ports on a PC when everything I plug into it besides my phone (depending on the cable) has a USB-A connector? Like how would I even use something as simple as a flash drive or Bluetooth/wifi/radio transmitter?
USB-C makes a ton more sense for mobile devices, docks, and charging, but not so much when you're plugging them into a suitcased size brick that doesn't move. I could see useful applications for something powered that needs a lot of bandwidth, but PCs also come with dedicated ports for all those peripherals too.
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Would make much sense. You still want USB-A ports for most peripherals as using an usb-c port to connect a single mouse would be pretty much wasting a port.
However adding a Thunderbolt4 port or two along side the usual USB-A ports would be nice.
Ofcourse you'd still want some type a ports, but I have 6 type a ports and a single type c on my rear io but i would definitely give up 1 or 2 a ports for 2 more type c.
I'd honestly love to see everything USB-C-ified. Would be great to finally just have one standard to concern yourself with.
Nobody tell them about the massively fragmented set of standards using the USB-C connection.
I know, but at least we'd only have one physical connector at that point. While there are indeed a lot of standards for USB C, many of them are not all that relevant in day-to-day use when you're mostly just looking to connect some basic USB peripherals like a mouse, a thumb drive or charge your phone.
I disagree.
More technical people would understand, but your average Joe would try to plug in their external monitor and RMA PC because it's not working, same with slow charging phone speed etc.
I'm honestly all in for keeping USB-A for basic I/O devices. Although inventing an USB-A female connector that works both sides and is backwards compatible would be neat.
Don't think this didn't happen for people that wished to copy something from or to an external drive, and RMAd as they found it to be too slow. They plugged it into a black usb 2.0 port instead of a red one because they thought it was dangerous. Ow wait, no. That motherboard manufacturer used green usb ports for USB3.2. What do you mean you didn't try it because you didn't know what they were for? Your hard drive cable has blue plugs, didn't you at least try the blue ports? No? Because there was a lighting bolt printed nearby... I understand you don't want to lose the data. Do you have a backup? ... You should. Ok, well you can test it with the mouse or keyboard. Yes, the top two usb ports do have the icons for those, but that doesn't mean... Oh, you already put the pc in the mail. See you in 2 weeks then.
Also, switchable usb-a is already a thing, but is very flimsy due to the necessity of moving parts.
The difference between different generations of USB-A are speeds. If user notices differences in speeds, they are way more likely to know the difference between USB versions.
The differences between USB-C and USB-A are capabilities. USB-C is already confusing for many people. My boss (IT Project Manager) thought he could use USB-C to connect his monitor, while he couldn't because his laptop doesn't support DisplayPort over USB-C.
There is already a huge mess with USB-C capabilities. Some of them are just glorified USB-A ports, some of them have DisplayPort over USB-C, some of them are Thunderbolt (with different versions or course), some of them are QC (with different versions - once again).
I can just imagine the confusion from users, who expect all of the USB-C ports in the motherboard to work the same way, but then only one or two ports from 8 total have DisplayPort capabilities.
"If it doesn't fit it means it's not supposed to go here" is a great way to tell the user what capabilities the port has.
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Standard USB type A ports are cheaper, and more importantly, STURDIER then USB C ports. This is extremely important for peripherals that do not need to be disconnected and reconnected often.
USB C is great for convenience for certain things, but it's a weaker port in terms of physical connection strength.
Weirder is that you can’t really find usb c mice and keyboards, though I really don’t know why.
Extra cost for no real benefit
Because motherboards are mostly USB A, because peripherals are mostly USB A, because motherboards are mostly USB A, bec...
There are a few, but certainly not many. And they mostly seemed to be aimed at plugging into Mac laptops. But at the moment, manufacturers can count on every computer made in the last 20 years or whatever having at least one USB-A port, and most computers still having zero USB-C ports. The options are to make it USB-C and pay extra to include an adapter, or just say the hell with it and make it USB-A. Or relegate yourself to basically selling to Mac users only.
Most manufacturers, naturally, will pick the second option.
USB-C is very hard to manufacture and expensive as fuck as a result.
thats why.
Especially when most devices don't need the bandwidth or power needs of USB-C.
Source? Why is it expensive?
Pretty sure this person is just talking out of their ass. I found one source from four years ago that showed a price difference of about a buck to manufacture. Yes, that is more expensive, but passing that dollar onto the consumer for some USB-C ports on a motherboard seems pretty reasonable, and by now I'm sure that gap has decreased significantly.
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I know for a fact that USB-c is about 1.5× mirco-b.
https://www.adafruit.com/search?q=usb%20breakout%20board
Since USB A is not a slave connector that are no comparable boards on adafruit. So I asked Bing AI:
According to the web search results, the cost of a USB-C connector on a motherboard depends on various factors, such as the manufacturer, the chipset, the data standard, and the features of the motherboard. However, based on some examples of motherboards with USB-C ports, the price difference between USB-C and USB-A connectors with the same speed (USB 2.0) is not very significant. For instance, the ASRock B550M-ITX/ac motherboard has one USB-C port and four USB-A ports, all with USB 2.0 speed, and costs around $120. The [ASRock B450M-HDV R4.0] motherboard has six USB-A ports, all with USB 2.0 speed, and costs around $70. The difference in price between these two motherboards is $50, but this is not only due to the USB-C connector, but also to other factors such as the chipset, the memory slots, the audio codec, and so on. Therefore, it is hard to estimate the exact cost of a USB-C connector on a motherboard with USB 2.0 speed, but it is likely to be less than $10.
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My kids laptop has 4 IIRC. Getting a PC motherboard with more than one on rear and one connector for front of case was impossible last I looked. I generally keep my pc’s for about 5 years and wish to future proof somewhat. It is beyond ridiculous at this point. Although, I haven’t tried to buy one for a few months so perhaps this has changed.
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Had the same feeling a year and a half ago, I was thinking that maybe as I was not on a next gen CPU I was just on an older model and that's why it was not very present. I only have one usb-c on my motherboard B550M Micro ATX
bandwidth and room on the board mainly
my thinkpad has two usb-c ports, both can be used for charging. i still prefer usb-a cuz i still use peripherals and drives i have right now. im not ready throw them away for the sake of "newer ports."
I like USB A for thumb drives and other legacy equipment but I definitely prefer more USB C. Right now, I have a connected to my laptop through it, one for charging and then 2 USB A for peripherals. I'd personally trade the other two USB A and use a small hub instead so I can charge my phone, watch and vape without a separate charger.
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