USB 2.0 PCI Card speed knowledge?

[SysRed]

I have installed a PCI USB 2.0 host controller card, which seems to run much slower than the motherboards (MSI K9NGM / MS-7252) USB host controller.

When using the USB connectors direct from the motherboard, I was getting a much higher data rate than when using the ones on the PCI card. Can you advise where the bottleneck is happening as i beleive that the PCI BUS has a data rate of 480Mps ?

I could transfer 250GB of data in 6 hours from the motherboards USB controller but now can only manage 280GB in 24 hours from the PCI card.

Many thanks

Rich

 

[wahnula]

You can't go by the spec of 480mbps as a useful stat...it's more a "max" stat. Like my old Nova had a speedometer to 120 mph but could only do 90mph on a regular basis . Your mainboard's ports are obviously tied to a faster bus than the PCI bus and/or have a faster path to the HDD. I would never expect a PCI peripheral to have an equal or faster path than on onboard controller.

The bottleneck is the PCI bus overhead.

Tony

Users helping Users...

 

[SysRed]

Thanks Tony, I appreciate you will never ever get the 'perceived' maximum on any kind of data transfer, i just wanted to know or to confirm that the bottleneck is the PCI BUS given that they are both rated at 480MBps. I'm off to find out the data rate of the onboard USB controller. Thanks Rich.

 

[BadBigBen]

Although Tony is correct about the speed... I would beg to differ about the onboard USB being on a different BUS than the PCI, both are controlled by the SOUTHBRIDGE and are tied into the PCI bus... now with that info, there is the possibility that the onboard USB ports are tied into the system with PCI-Express speeds/standards, which makes them faster than any PCI card can ever be...

now, the bottleneck could also be IRQ related, e.g. shared IRQ with the GFX card or MEM controller, etc. could hamper transfer rates, and some if not most mainboards have two types of PCI SLOTS, Master and Slave... Slave ports can be problematic with certain PCI cards, e.g. TV Tuners or any which need high data transfers...

suggestion: try the PCI USB 2.0 card in another SLOT and retest the speed...

Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

How to ask a question, when posting them to a professional forum.

 

[SysRed]

Thanks ben, i'll check it out

 

[BadBigBen]

question: with a total of 8 USB ports (4 back & 4 front), why is it necessary to install a separate PCI USB card?



Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

How to ask a question, when posting them to a professional forum.

 

[SysRed]

PostBadBigBen Wrote
question: with a total of 8 USB ports (4 back & 4 front), why is it necessary to install a separate PCI USB card?

Fair question, The USB ports on the MB are no longer working (neither is the infrared which i understand uses the same controller) Also the box is a small form factor media centre therefore it only ever had 4 ports (2 front, 2 back) although the MB has ability to run 8. It took me a while to find a half height PCI card which also had header pins so i could use the front ports, i had to order one from the States.

 

[BadBigBen]

SysRed - Oh, I see... that is a bummer...

PS: mind if I ask, where you hail from?


Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

How to ask a question, when posting them to a professional forum.

 

[SysRed]

BadBigBen (MIS) Wrote
SysRed - Oh, I see... that is a bummer...
PS: mind if I ask, where you hail from?

Sunny (wet) Spain

Rich

 

[BadBigBen]

Rich - spain, hmmm, it probably would have been cheaper to order from the EU, e.g. Germany, NL, or UK, unless you are in the MIL... but I digress, and it's off topic...

as to the USB not working, have you checked the BIOS settings?

Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

How to ask a question, when posting them to a professional forum.

 

[SysRed]

Ben - Yes checked the BIOS, ran Micro 2000 diag software on the PC, reports back there is no USB installed, the reason i went the PCI card route. To be honest i could not find a supplier in the EU that had a half height card with the header pins to attach the the front ports. I'm not unhappy with my purchase from the states, and yes, subsequently i have found somewhere, always the way, never mind.

 

[BadBigBen]

I'm not unhappy with my purchase from the states,

Hey, no problem there...

and Ok about the USB & BIOS, just checking that nothing was overlooked...

Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

How to ask a question, when posting them to a professional forum.

 

[cdogg]

Rich,
An important point to keep in mind is that the PCI bus is not as efficient as a direct link to the Southbridge, which is the difference between an add-in PCI card and the motherboard's onboard ports. This is because PCI is a parallel inteface that is limited to one-way transfers that is shared among all devices on the PCI bus. IRQ wait-stop requests can easily saturate the bus especially when there is a lot of data that needs to access the hard drive or other components that are not directly attached to the PCI interface.

Also, you should be aware of the speed terminology. 480mbps (megabits per second) is the same as 60MB/s (megabytes per second). Actual transfer rates on USB 2.0 is usually peaks around 40MB/s due to overhead and other issues. The standard 32-bit 33MHz PCI interface can transfer up to 133MB/s. At first glance it would seem more than capable to handle USB 2.0, but for the reasons I've already mentioned, it's just not as efficient.

Although I would expect the PCI card to be slower, I wouldn't expect it to be almost 4 times slower as you've shown in your observation. That seems quite a bit off. There might be something else in play here causing the slow transfer speed.

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Einstein
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[SysRed]

cdogg, thanks for the explanation, I was aware that there are 8 bits to every bite, however I must admit in my ignorance I had wrongly assumed that USB 2.0 (theoretically) was 480MB/s rather than mbps!!! I'm going to test the card on another computer and see what the results are, cheers again Rich.

 

[cdogg]

No problem. Doing the math using 40MB/s, the fastest the transfer can occur will be right under 2 hours. However, the transfer will likely take a lot longer depending on the performance of the hard drives and what was discussed above about PCI. Anything higher than 5-6 hours though would be a surprise...