USB 2.0 flash drive on USB 1.1 port

Posted on 2003-02-28
Medium Priority
Last Modified: 2010-04-03
Will a USB 2.0 flash drive work on a USB 1.1 port?  Also, the description of the drive says "bulk-only transport of USB mass storage class support PIO mode 4".  What does that mean?
Question by:tirving
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Accepted Solution

kannabis earned 100 total points
ID: 8043253
yes it will work since USB 2.0 is backwards compatible with 1.1.


Short for Programmed Input/Output, a method of transferring data between two devices that uses the computer's main processor as part of the data path. ATA uses PIO and defines the speed of the data transfer in terms of the PIO mode implemented, as shown below: PIO Mode Data Transfer Rate (MBps)  Standard
0 3.3 ATA  
1 5.2 ATA  
2 8.3 ATA  
3 11.1 ATA-2  
4 16.6 ATA-2  
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Assisted Solution

by:Prester John
Prester John earned 100 total points
ID: 8043461
Just a comment:
PIO has generally been abandoned in favor of DMA [direct memory access] for increased data transfer/time.
This flash drive is PIO? Interesting.
What brand is it?

Author Comment

ID: 8043606
Kannabis:  thanks for your answer.  Brand is unknown.  I want to purchase it from comready.com who doesn't list the manufacturer.  Is this mode significantly deficient compared to DMA?  What does bulk only mean?
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Expert Comment

by:Prester John
ID: 8044672
I'm not certain about the "bulk only" thing. Maybe that's a reference to burst rates. see next.

As kannabus said: the fastest PIO mode (4) has a max. transfer rate (burst) of 16.7 MB/s.

Sustained transfer rates are ALWAYS slower.

The slowest Ultra DMA [UDMA] mode 0 has the same burst rate as PIO 4 & the current mode has a burst of 133MB/s
There is a secondary advantage to DMA/UDMA.
They bypass the CPU entirely [ hence the term "direct memory access"].
This frees up the CPU and, consequently, most of the rest of the system. Doesn't bog the computer down nearly as much.

I would look around a bit.

BTW kannabus deserves the points here. ;-)

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Expert Comment

ID: 10097476
No comment has been added lately, so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area that this question is:

Split between kannabis and StoneG

Please leave any comments here within the next seven days.


EE Cleanup Volunteer
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Expert Comment

by:Prester John
ID: 10097736
K by me if ok w/kannabis.
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Expert Comment

by:Prester John
ID: 10150516

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