|
|
|
|
У Cypress есть статья и резултаты тестов для FX2.
file: lthbandwidth_meter.pdf
Data was taken on a desktop computer
running Windows XP, with the USB 2.0 Host Controller
on a PCI card. To put the bytes-per-packet numbers into perspective,
the maximum theoretical high-speed bandwidth over
USB 2.0 (from the specification) is 13 BULK packets per microframe.
This represents a maximum bandwidth of:
13 * 512 / 125 µs = 53.24 MBytes/sec [theoretical max.]
(13 packets per microframe, 512 bytes per packet, 125 µs per
microframe.)
The test achieved a peak transfer rate of 5 packets in
a micro-frame, giving a peak bandwidth of:
4 * 512 / 125 µs = 20.48 MBytes/sec [measured]
The average transfer rate is calculated by noting that the transfer
took four microframes, or 500 µs, so the average rate was
8192 bytes in 500 µs, or 16.386 MBytes/sec.
These numbers are typical for the architecture shown in Figure
1. Using the bandwidth meter to test more advanced motherboard
chip sets yields better performance numbers. For example,
an MSI 845Gmax motherboard, which uses the Intel ICH4
chip with integrated USB 2.0 controller, performed an 8192
byte IN transfer using two microframes of 8 packets per frame
[08 08], and a 16384-byte transfer using four microframes,
transferring [09 0A 0A 03] packets per microframe. The peak
value of 10 packets in a microframe is respectably close to the
13-packet theoretical limit.
10* 512 / 125 µs = 40.96 MBytes/sec [measured]
E-mail: 
info@telesys.ru
