I believe part of the problem on the Keyboard/Mouse may be how inputs or interrupts are handled. Basically each cycle or so the CPU asks the keyboard/mouse if it has anything for it to process. Much like kids on a road trip 'ARE WE THERE YET?'obarthelemy wrote:Those speeds are extremely theoretical:
1- both interfaces have overhead, USB a lot more than SATA. So that 480 Mbps pipe really doesn't ever deliver more than around 350 of useful data.
2- USB uses a lot of CPU cycles to manage the connection and handle the data. Someone's noticed that even with just a keyboard and mouse connected, USB handling uses up to 20% of the Pi's CPU cycles. That's with only 2 peripherals, and very little data to handle. The current USB driver is ... not very good.. but building a better one seems hard.
Thanx for your reply.CCitizenTO wrote:I think people are disappointed with USB3.0 peripherals on the RPi because to maintain compatibility they will fall back to USB2.0 speeds thus they wont get the same performance out of them as they would if they hooked them up to their newer desktop or laptop machines that have a USB3.0 port.
Chart of USB Speeds
USB1.0: 15Mbps (1.88MB/s)
USB2.0: 480Mbps (35MB/s)
USB3.0: 5Gbps (625MB/s)
Chart of SATA Speeds
SATA1: 1.5Gbps (0.19GB/s)
SATA2: 3Gbps (0.34GB/s)
SATA3: 6Gbps (0.75GB/s)
Also I dont think the Pi can handle speeds like 5Gbps. Which is probably why it does not have a 1Gbps Ethernet Adapter (aside from cost considerations as well). That said I've never managed to download something faster than maybe 100-200MB/s on my connection to the internet so that doesnt really matter.
Also you have to keep in mind that conventional drives (rotating spindle) have hit their peak in terms of data throughput. They are big, inexpensive but SLOW. SSDs are small, expensive but FAST. This is ofcourse assuming the same pricing points. There are 2TB SSDs out there that cost you an arm and a leg.
It may just be you have a USB3.0 SATA dock laying around or a USB3.0 one cost as much as a USB2.0 one. But functionally working with the Pi and working with conventional drives they're equivalently the same because it wouldnt take advantage of the higher speeds USB3.0 has to offeranyways.
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