Re: Interesting speed benchmarks

Hans Petter Selasky wrote:
On Friday 26 January 2007 13:41, Stefan Ehmann wrote:
On Friday 26 January 2007 13:35, Andrew Pantyukhin wrote:
On 1/26/07, Stefan Ehmann <shoesoft@xxxxxxx> wrote:
On Friday 26 January 2007 11:00, Alexey Karagodov wrote:
what manufacturer says about usb speeds?
that is the question
Well, "up to 56MB/s" which is pretty much full USB2 speed.

It is called high speed USB, and it can go up 53 MB/s with a payload of 512
bytes per packet according to "Table 5-10. High-speed Bulk Transaction
Limits" in the USB 2.0 specification. The table does not say anything about
whether this include bit-stuffing or not. If bit stuffing is not included,
then you have to divide this value by 1.20 approximately for the worst case,
all 1's. 53 MB/s div 1.20 = 44 MB/s.

But writing it on the box doesn't mean the speed can actually be
reached.

Benchmarking on windows might be interesting, but I don't know how to
measure raw disk io on windows.
Format the disk, copy a large file to/from it, divide
its size by time spent, add the word "approximately" :-)
I'd rather not format a drive with my backups and other stuff on it :-)

Results with the new USB stack*:

Changing the interrupt delay from 2 microframes to 1 microframe gave me
2MBytes more per second on the EHCI controller.

I connected two high speed "umass" capable devices to the same EHCI controller
on my computer, and did a "dd" on both devices at the same time, with a block
size of 131072 bytes.

The one device transferred 22 MB/s. The other device transferred 16 MB/s.
Summed up this yields 38 MB/s. Used alone these devices can transfer 27 MB/s
and 20 MB/s. It seems clear that the EHCI controller is saturated at 38 MB/s.

%dmesg |grep ehci
ehci0: <Intel 82801DB/L/M (ICH4) USB 2.0 controller> mem 0xe0100000-0xe01003ff
irq 10 at device 29.7 on pci0
usb3: <Intel 82801DB/L/M (ICH4) USB 2.0 controller> on ehci0
%


Just FYI.

I get about the same performance on my laptop running Windows XP when
moving between local 100 mb 5400 rpm ATA and 250 mb 7200 rpm USB2.0 disk.
I have the same controller.

--
Sten Daniel Sørsdal

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