What difference does it make whether the computer uses USB Ethernet Adapter, or a network card?

Question

Just what the title states.

I'd like to know what difference it makes to the modem/switch, speed, power consumption whether the computer is connected by a USB Ethernet Adapter instead of a physical network card installed into a PCI slot.

As a corollary, it would be nice to know which you would recommend to a nouveau at networking.

Answer 1

Computer technician weighing in here...

Just as the other posters have said, your best bet is an internal network card. This is for the following reasons:

1. USB IO is controlled by the CPU and USB network cards cannot use DMA--this means CPU usage grows with network traffic;
2. The USB bus is shared, which means one thirsty peripheral can (in a severe case) impact the performance of other peripherals such as hard drives and may affect the latency of HID peripherals such as mice and keyboards;
3. There are very few ethernet chipsets and they all have solid, tested drivers which are used directly to support PCI cards--when the USB interface is added, an additional driver is necessary to "glue" the chipset to the USB bus;
   • Drivers are easy to mess up, particularly when small companies are involved.

In theory, systemic power usage would be greater for a USB adapter because of the additional CPU overhead that cannot be off-loaded to a dedicated chip. This may not be the case for high-throughput cases, though (read: I am really just making an educated guess).

Answer 2

I would always recommend a dedicated card/adapter over anything USB whenever it is practical.

USB is good for convenience, but should never be used for critical components where it can be helped.

I do not have any figures regarding power or speed.

That being said, I am sure it "can" support full 100Meg networking speed - I am not entirely sure and would doubt about gigabit speed.

If you go back a few years to when many ISPs gave USB networking, they were always causing problems. The most common is that when the CPU is being used intensively (e.g. above 80%), it wasn't uncommon to see packet loss and other errors.

Answer 3

A USB Ethernet adapter IS a network "card". They are the same for all intents and purposes. I am not sure which takes more power, a PCI slot or USB, but it is negligible considering the DC voltages that used internally.

I still prefer an internal network card, but only because I don't like things handing off my computer, if at all possible. And such things can break off.