Using multiple USB ports at one for heavy data transfer?

Twisted_Sister

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I have a question that I think is mostly MOBO related.

First, do those internal Compact Flash card drive readers provide a significant boost to downlaod speeds vs. USB 2? I typically have to download about 10-15GBs of data.

Also, can a MOBO handle multiple CF cards being downloaded at the same time to different USB ports? Or does it just reallocate bandwith between the USB ports in use?

So if I wanted to download (2) 2GB CF cards at once, while uploading data to an external hard drive... is this possible at full USB speeds on each port?

Thanks
 

Slobogob

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As far as i know all those USB connectors share the same bandwidth. USB2 should have an available total bandwidth of 480 Megabit per Second. That is far more than a single device can saturate.
I don´t think that the Speed of the USB2 Bus can be a limiting factor for a single device yet. For two devices, it could be a bottleneck already - largely depending on the devices you connect.

You should read this.
 

Twisted_Sister

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As far as i know all those USB connectors share the same bandwidth. USB2 should have an available total bandwidth of 480 Megabit per Second. That is far more than a single device can saturate.
I don´t think that the Speed of the USB2 Bus can be a limiting factor for a single device yet. For two devices, it could be a bottleneck already - largely depending on the devices you connect.

You should read this.
Thanks! At the end of the article it said this....

"Practically speaking, if you're running out of USB bandwidth, just pop in a USB 2.0 PCI card, and another 480Mbps pipe will be at your service."

So if I add PCI card, I can effective have 860Mbps of pipe?
 

hergieburbur

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Well, in theory yes, but that depends on two things:

A PCI card shares its bandwidth with all other PCI devices (66 MB/s or 528 megabits/s), some of which may be integrated into the mobo. Which leads to:

If the USB 2.0 header on your mobo already uses the PCI bridge (depends on your mobo), then you would actually be slowing things down by using the extra card.
 

derek2006

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An external hard drive can saturate it. A usb flash drive can't though. 480 Megabits is 60 megabytes. Sata 2 is 3 Gigabits which is 3000 megabits or 375 megabytes.
 

hergieburbur

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An external hard drive can saturate it. A usb flash drive can't though. 480 Megabits is 60 megabytes. Sata 2 is 3 Gigabits which is 3000 megabits or 375 megabytes.
Thats incorrect.

Your numbers are right, but there is not one single external or internal SATA Drive that can come close to those numbers. There are only a few drives out there that can saturate a SATA 1 link, and then only in short bursts. That's why the WD Raptor drives only use a SATA 1 interface.

</Edit>I should say that comes close to those SATA numbers. Fast drives CAN saturate a USB-2 Link, but it is semi-irrelevant whether they are SATA or PATA drives.</Edit>
 

vic20

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Each pair of 2 USB connectors are shared.

So you would need 3 seperate headers to hook up 2 card readers and one external drive to avoid sharing of bandwidth.

If are are using internal card readers, this is easy, as each internal card reader uses a full header anyway.

If you are talking external card reader, just don't plug them both into the same port.

For example, say you have six ports.
Just plug each device into ONE of the pairs
╔╗╔╗
║║║║ <------ Card reader one
╚╝╚╝
╔╗╔╗
║║║║ <------ Card reader two
╚╝╚╝
╔╗╔╗
║║║║ <------ External hard drive
╚╝╚╝

Now keep in mind an external USB 3.5" hard drive can saturate one pair/port (many new 7200 drives are hitting 80MB/s read/write speeds).

But high speed (133/150/166x) CF/SD cards only run at 15MB/s, so all the controller bandwidth in the world won't help much here.

[EDIT] Every chipset has VERY different performance regarding USB/Firewire/SATA, and they are not 100% effecient. Also, the USB to IDE/SATA bridge inside card readers and USB enclosures themselves will vary quite large in performance.

Read the subsystem portion of motherboard reviews and you will get the idea. Intel chipsets seem to have very good USB\SATA performance. ICH8 would be a good choice. Also, read some reviews on enclusures and prepackaged external hard drives.
 

derek2006

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I know there is not one Hard drive to come close to the bandwidths of Sata 2 but HD's do go over the usb bandwidth. My sata drive does about 74mb/s or so. And there is other data being transfered too. I also do know that it is just theoretical. The USB is just theoretical also and you can't actually achieve 480 megabits. If I put my ATA 100 drive back into the external closure it does close to 40 MB/s. In my computer it can do 53 MB's. So the USB bottlenecks external HD's. I put the numbers in there just to give an idea of how slow it is to Sata and how USB may limit it .
 

hergieburbur

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I wasn't necessarily countermanding you as I was clarifying your post. I understood what you meant, but it could be very misleading to people who didn't know better. I was not aware of whether or not you knew better either way.
 

derek2006

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Ya I understand what you mean. It can be misleading. It wasn't a very good post. I should of explained better but I was kinda in a hurry to get some where.
 

Twisted_Sister

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Each pair of 2 USB connectors are shared.

So you would need 3 seperate headers to hook up 2 card readers and one external drive to avoid sharing of bandwidth.

If are are using internal card readers, this is easy, as each internal card reader uses a full header anyway.

If you are talking external card reader, just don't plug them both into the same port.

For example, say you have six ports.
Just plug each device into ONE of the pairs
╔╗╔╗
║║║║ <------ Card reader one
╚╝╚╝
╔╗╔╗
║║║║ <------ Card reader two
╚╝╚╝
╔╗╔╗
║║║║ <------ External hard drive
╚╝╚╝

Now keep in mind an external USB 3.5" hard drive can saturate one pair/port (many new 7200 drives are hitting 80MB/s read/write speeds).

But high speed (133/150/166x) CF/SD cards only run at 15MB/s, so all the controller bandwidth in the world won't help much here.

[EDIT] Every chipset has VERY different performance regarding USB/Firewire/SATA, and they are not 100% effecient. Also, the USB to IDE/SATA bridge inside card readers and USB enclosures themselves will vary quite large in performance.

Read the subsystem portion of motherboard reviews and you will get the idea. Intel chipsets seem to have very good USB\SATA performance. ICH8 would be a good choice. Also, read some reviews on enclusures and prepackaged external hard drives.
Thanks everyone! And this post was very helpful. :D
 

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