A sessão de perguntas e respostas de hoje nos é oferecida por cortesia do SuperUser, uma subdivisão do Stack Exchange, um agrupamento de sites de perguntas e respostas conduzido pela comunidade.
Foto cedida por Jack Zalium (Flicker).
A questão
Leitor de superusuário philipthegreat quer saber se conectar um mouse a uma porta USB 3.0 fornecerá qualquer benefício de velocidade ou não:
I am looking for an authoritative answer backed by data. A friend asked me the other day if he would benefit from plugging his mouse into a USB 3.0 port instead of an available 2.0 port. I flippantly replied that it would make no difference at all. I am certainly not the only one to think that. See these responses to the debate on:
- Tom’s Hardware
- Overclock.net
- Logitech Forums
- Yahoo Answers
Intuitively, I do not think data throughput should be an issue. Mice worked fine over a serial port, and those transfer at a maximum of 112.5 Kbps. USB 1.0 runs at 1.5 Mbps (slow) or 12 Mbps (fast). USB 2.0 can handle 480 Mbps and 3.0 can reach 5 Gbps.
But what about response speed? Are there any published studies of response time between USB 2.0 and 3.0 ports?
My question is, was I right? Would it matter if I have a really fancy mouse? Can my friend safely blame his loss in League of Legends on his slow USB port?
Conectar um mouse a uma porta USB 3.0 faz diferença ou não?
A resposta
Os contribuidores do SuperUser, AFH e Michael Hamilton, têm a resposta para nós. Primeiro, AFH:
- A mouse is a slow device (the old PS/2 standard was RS232C-based), so USB 1.0 is more than adequate.
- USB 3.0 ports have extra connectors for high-speed transfers, but also have standard USB 2.0 connectors for backward compatibility.
- Unless your mouse has these extra connectors (and I can not imagine any mouse that has them), it will connect via USB 2.0 in a USB 3.0 connector.
So you are entirely correct. Plugging a mouse into a USB 3.0 connector confers no benefits whatsoever. If a mouse responds slowly, it is because something else is hogging the CPU to the detriment of the mouse driver.
Seguido pela resposta de Michael Hamilton:
We need to take a look at the mouse’s polling rate. From that we can have a better idea of how much data is being transmitted. If a mouse has a 100hz polling rate, it is sending data to the computer 100 times a second.
A standard mouse will send a 3-byte packet containing info on X/Y position information as well as button information. Considering that 3 bytes are transferred each cycle of the polling rate, you could have 300 bytes per second being transferred.
By default, the USB polling rate is 125hz, so by our logic, the amount of data being transmitted is 375 bytes per second.
Based on this, I do not think USB 3.0 is going to be any more beneficial than USB 2.0 (or even 1.0).
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