USB 2.0 PCI card question.


Overclocked Like A Mother
Hi Guys,

I am asking this for a friend. He has an older first generation P4 computer, current USB ports on mobo are 1.1 spec. He bought an Adaptec USB 2.0 PCI card and he can't get it to work at 2.0 speeds (480Mbits/sec.), only 1.1 speeds. He figures it is his drivers as he is trying everyone of them from Adaptec home page, to no avail. I am trying to tell him that he can't get USB2.0 Data Transfer Rate because of the PCI bus cannot handle that. The website makes it sound like it can. Can It? Wants to use it for an external HD.



Staff member
Political User
I'm using a USB 2.0 PCI card for my mp3 player, as I only have USB1.1 on my mobo, and it works brilliantly. I just plugged it in and it installed itself in a minute and that was that, no problems or hassle. I'm using XP SP2, on an Abit KT7A mobo using some sort of VIA chipset.
I would guess that a USB 2.0 PCI card will never get quite the performance of the USB ports built into a USB 2.0 mobo, but this is still many many times quicker than my standard USB 1.1 ports.
In short, it should work, maybe your friend could try downloading the latest mobo and USB drivers for his system if he gets problems.

Son Goku

No lover of dogma
It should work, as others have mentioned. You see, the card itself should be supporting USB 2.0... But what the mobo sees is the interface, aka a PCI card, rather then a USB bus. It should be much like my Ultra 160 SCSI card (except that of course, a 32-bit 33 MHz PCI bus couldn't sustain 160 MB/sec data transfer), and reason to get an expansion card for another, or newer bus...

Time to troubleshoot this puppy. What OS, does the card have device drivers, are they loaded, etc?


OSNN Veteran Addict
Lets start over - What do you mean "he is not getting USB 2.0 speeds"?

Does Device Managler/Explorer show the device connected as USB 2.0?
Is it 10% slow, 50% slow, or running at USB 1 speeds?
Has he converted from serial to bytes and added protocol overhead?
What kind of device is it? External HD, Camera, etc.

Assuming the device and the PCI card are connected as USB 2.0 protocol he will be slightly bandwidth limited by the 33 mHz, 32 BIT PCI card interface (<1000 mbits/sec theoretical max) assuming that one card slot can't use the whole bandwidth.

Conversion from bits to bytes and protocol overhead will divide the rated USB 2.0 speed by 10 times. i.e. 48 mBytes/sec.

The advantage to USB 2 (just like 100MHz and 1 gig ethernet) lies in being able to connect several users simultaneously and having them all get goods speeds. Don't expect to see the theoretical maximums on any serial protocol.

PS The P4 FSB of 533mHz x 32 BITs should be plenty of bandwidth, it's not an issue.
Last edited:


Overclocked Like A Mother
Thanks guys,

I found out what exactly what was happening over there. Just got off the phone with him. He has XP SP2, and when he installed the card, Device Manager picked it up, Then he proceeded to install OEM drivers that are not working with SP2. He never actually tried using the thing just with SP2 drivers only. Now that he uninstalled it and reinstalled it without the OEM drivers, it is working fine now.

Thanks again,


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