Why PCI Express USB 3.0 card is slower than built-in ports.
PuppyThis forum is for the discussion of Puppy Linux.
Notices
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
Get a virtual cloud desktop with the Linux distro that you want in less than five minutes with Shells! With over 10 pre-installed distros to choose from, the worry-free installation life is here! Whether you are a digital nomad or just looking for flexibility, Shells can put your Linux machine on the device that you want to use.
Exclusive for LQ members, get up to 45% off per month. Click here for more info.
Why PCI Express USB 3.0 card is slower than built-in ports.
Why my PCI Express USB 3.0 card is slower than built-in
ports.
Quote:
So the PCI Express slot is already the gating item.
PCI Express cannot even go at the link rate, due
to limited buffer space on the hub bus buffer. Only
a chipset USB3 port runs at the full rate. The
"add-on" designs are typically passing through
a x1 interface, and then you have to take the
buffer into account.
When a Southbridge USB3 logic block is connected
to the Northbridge, it uses at least the equivalent
of a x4 connection. Even if the connection runs at
50% efficiency, you get a x2 rate, and enough to run
at least a benchmark test at full speed. Whereas,
plugin chips tend to have x1 interfaces, and if the
bus efficiency isn't 100%, then the max USB3 rates
are limited. This is why add-on cards are inferior,
because the company making the chip didn't put an
x2 or x4 interface on it.
And so, a bandwidth report seeing more than is
possible, tells you there is a system file cache
present.
*******
From an administrator account, you could try
echo 3 > /proc/sys/vm/drop_caches
where the possible values are
1 = pagecache
2 = dentries,inodes
3 = both
Doing that, should make no different to
Linux program running speed. But what it
can do, is flush the system file cache.
To be done just before a benchmark step.
To make the benchmark more honest.
LinuxQuestions.org is looking for people interested in writing
Editorials, Articles, Reviews, and more. If you'd like to contribute
content, let us know.