USB 2.0 limited to 20MB/s on eee pc 701 netbook?

13ren

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Sep 13, 2013
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Is the USB 2.0 port of the eee PC 701 (the original) limited to 20MB/s in some way?

In practice, most USB 2.0 memory sticks give around 20MB/s, even though the spec allows for much higher (around 500MB/s IIRC).

USB 3.0 memory sticks of course give higher performance in a USB 3.0 - but interestingly, many of them also claim to also give higher performance in USB 2.0 ports (IIRC, around 30MB/s) - though of course not as fast as in a USB 3.0 port.

My question: I have an old eee PC 701 (the original one). If I buy one of these faster USB 3.0 sticks, will it be fast in the eee? Or... is the eee's USB 2.0 port limited in some way?

Note 1: even its internal SSD only gives around 20MB/s (which is connected by USB)... I would have expected it to be much faster than an external drive.

Note 2: I've also tried an external HDD, via a USB adapter, and that also only gave around 20MB/s, even though the drive itself is much faster. But this doesn't prove the eee's USB port is slow, because it might be due to the adapter...

Thanks for any help! (also, if anyone can suggest where else to ask eee questions... there used to be an eee forum but it's gone now...)
 

cklaubur

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Oct 4, 2006
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Your USB speeds are about what they are expected to be. USB 2.0's maximum bandwidth is 480 Megabits/second, divided by 8 gives you a raw bandwidth of 60 Megabytes/second. Overhead for the signaling protocols and USB functions cause the effective bandwidth to be about 30 Megabytes/second.

Plugging a USB 3.0 device into a USB 2.0 port will give you the same speeds as a native USB 2.0 device. The internal hardware will be faster, but it's like a fast car on a busy two-lane road.

In short, you are being limited by the USB ports, and unfortunately, there isn't much that can be done about it.

Casey
 

cklaubur

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Oct 4, 2006
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Your USB speeds are about what they are expected to be. USB 2.0's maximum bandwidth is 480 Megabits/second, divided by 8 gives you a raw bandwidth of 60 Megabytes/second. Overhead for the signaling protocols and USB functions cause the effective bandwidth to be about 30 Megabytes/second.

Plugging a USB 3.0 device into a USB 2.0 port will give you the same speeds as a native USB 2.0 device. The internal hardware will be faster, but it's like a fast car on a busy two-lane road.

In short, you are being limited by the USB ports, and unfortunately, there isn't much that can be done about it.

Casey
 

13ren

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Sep 13, 2013
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Ah, thanks, I was thinking MB, but it's Mbit!

According to wikipedia, USB 2.0 has 480 Mbit/s (effective throughput up to 35 MB/s) - so my hope of getting 30MB/s instead of 20MB/s seems reasonable. USB 2.0 itself is not limited to 20MB/s.

Googling further, I found someone got close to this theoretical maximum on an eee PC:

Code:
Device 	                       	Read MB/s  Write MB/s 	Benchmark 	   	 	Submitted 
Corsair Flash Voyager 4GB 	34.90 	   11.7 	HD Tach RW 3.0.1.0 	 	eclipse95
Corsair Flash Voyager 4GB 	33.40  	   10.1 	Flash Memory Toolkit 1.11 	eclipse95
 
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