Thank you for using the
Dell Community Forum. Do the two USB2 ports on the D600 connect internally to the same USB2 controller via an internal hub, or is each port wired to its own controller? Their both connected to the same controller.
Will slow devices still soak up bandwidth time and tie up the bus for everything. Yes, there is only a certain amount of bandwith and all USB devices connected to the system have to share it.
Is the hub supposed to buffer slow requests and pass them along as fast requests? The internal USB hub does buffer USB data for several reasons, but it does not increase the speed
of data delivered at USB 1.1 speeds.
Would replacing the slow devices' hub with a USB2.0 hub make a difference? No, because the end device is still a USB 1.1 device.
A USB hub whether internal or external will match the speed of the device which is sending the data.
So the hub will read the 1.1 speed of the USB device and match that speed to make sure the device can recieve the
information accurately. When the USB device is the same speed as the USB hub, then the hub simply repeats the singal
and does not have to match the speed.
In simple terms:
If you have a USB 1.1 device, the transfer of data between the device and the USB controller will be at 1.1 speed.
If you have a USB 2.0 device, the transfer of data between the device and the USB controller will be at 2.0 speed.
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The information above is based on the USB 2.0 specifications found on www.USB.ORG.
Role of Host PC software.
Current applications software on the PC continues to operate with USB 1.1
peripherals and is unchanged. The system software will comprehend the
increased capabilities of USB 2.0 peripherals so that it can optimize
performance. The system software will also detect sub-optimal configurations,
i.e. a USB 2.0 peripheral attached to a USB 1.1 hub, and will alert the user and
recommend a better configuration for attaching the peripherals. New
applications will be written to take advantage of the higher speed capabilities and
ease-of-use of USB 2.0 peripherals and drivers.
Role of the hub.
A USB 2.0 hub accepts high-speed transactions at the faster frame rate and
must deliver them to high-speed USB 2.0 peripherals and USB 1.1 peripherals.
This data rate matching responsibility will require some increased hub complexity
and temporary buffering of the incoming high-speed data. In the simplest case of
communicating with an attached USB 2.0 peripheral, the hub repeats the highspeed
signals on appropriate USB 2.0 upstream and downstream cables just as
a USB 1.1 hub repeats full and low-speed signals today on USB 1.1 devices.
This allows USB 2.0 peripherals to utilize the majority of USB 2.0 bandwidth.
To communicate with USB 1.1 peripherals, a USB 2.0 hub contains a mechanism
that supports the concept of matching the data rate with the capabilities of the
downstream device. In other words, the hub manages the transition of the data
rate from the high speed of the host controller to the lower speed of a USB 1.1
device. This feature of USB 2.0 hubs means that USB 1.1 devices can operate
along with USB 2.0 devices and not consume disproportionate amounts of USB
2.0 bandwidth. This new hub architecture is intended to be as simple and cost
effective as possible, and yet deliver the full capabilities of 1.1 connections.
The new USB 2.0 hub will be completely defined in the USB 2.0 specification
providing clear implementation guidelines for hub vendors and allowing a single
software driver to service USB 2.0 hub products from multiple vendors.
Role of the peripheral.
Current peripheral products do not require any changes to operate in a USB 2.0
system. Many Human Interface Devices, such as mice, keyboards and game
pads will not require the additional performance that USB 2.0 offers and will
remain as full or low speed peripherals as defined by USB 1.1.
The higher data rate of USB 2.0 will, however, open up the possibilities of
exciting new peripherals. Video-conferencing cameras will perform better with
access to higher bandwidth. Next-generation, higher-speed and higher
resolution printer and scanner devices will be enabled at the high-end. High
density storage devices such as R/W DVD, and high capacity CDROM jukeboxes
will also be enabled by USB 2.0. These devices require minor changes to the
peripheral interface, as defined in the USB 2.0 specification. Overall, the
additional cost to support USB 2.0 is expected to be minimal to the peripheral.
Both USB1.1 and USB 2.0 devices will inter-operate in a USB 2.0 system.
Summary
The USB Specification is currently at Version 1.1 and supports a wide range of
products. Many vendors are moving towards USB, drawn by its inclusion on
virtually all PC platforms and its ease-of-use. More and more types of innovative
new peripherals are taking advantage of USB, which further enhance the
available USB product portfolio.
The version 2.0 specification that is under development is an evolutionary step
that increases performance capabilities at low cost for USB peripherals in a
backwards compatible fashion. It is expected to broaden the market for new and
higher performance PC peripherals, and supercede USB 1.1 on future PCs.
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suppose a slow USB1.1 device with lots of data to transfer (say, a 2 year old scanner) is connected to a usb2 hub along with other slow peripherals (say, a mouse, a keyboard, etc), and that hub is connected to one of the D600's two USB ports.
suppose a single fast usb2 device is connected directly to the D600's other USB port.
Suppose further that the scanner is performing a scan, and transferring data to the notebook at usb1.1 speeds, and the hard drive needs to transfer data at the same time.
What you're saying is that by definition, a USB2 hub isn't supposed to think, "Hmmm. This old slow peripheral is transmitting lots of data and taking a long time to do it. My upstream connection is a lot faster, though, so instead of just blindly soaking up all the upstream bandwidth while this slow peripheral is taking its sweet time and making everybody else who needs access to the bus wait, I'll just buffer it for a few milliseconds, then relay it on to its final destination at the faster rate I'm capable of. That way, if anything else needs to transfer data along the bus, it'll have more opportunities to do so because the bus won't be held up while I'm buffering the next chunk of data from this old slow peripheral.
Furthermore, both USB2 ports on the D600 share the same bus, so while the scanner is trickling data onto the bus, the hard drive will be forced to metaphorically tap its foot impatiently like someone who's in a hurry at a grocery store, stuck behind an old lady who can't make up her mind which scratch-off lottery ticket she wants to buy -- holding up the whole line of people behind her who know EXACTLY what they want in the meantime.
Right?
Oh well. I guess that makes the decision to get a cardbus firewire card a lot easier ;-)
The USB controller will split up the bandwith to accomidate both devices.
But, the USB HUB will not buffer the USB 1.1 signal to make it faster.
The signal must stay at the speed of the USB device which is sending it, in order for that
device not to get confused. When the USB hub buffers the data, it buffers it to match the
speed of the USB device, not to increase the speed.
So, the USB hub will simply repeat a signal it gets from a USB 2.0 device.
But, the hub will buffer the signal from a USB 1.1 device to make sure it is kept at a constant USB 1.1 speed.
Karell
2 Intern
•
2.5K Posts
0
November 19th, 2003 16:00
Thank you for using the Dell Community Forum.
Do the two USB2 ports on the D600 connect internally to the same USB2 controller via an internal hub, or is each port wired to its own controller?
Their both connected to the same controller.
Will slow devices still soak up bandwidth time and tie up the bus for everything.
Yes, there is only a certain amount of bandwith and all USB devices connected to the system have to share it.
Is the hub supposed to buffer slow requests and pass them along as fast requests?
The internal USB hub does buffer USB data for several reasons, but it does not increase the speed
of data delivered at USB 1.1 speeds.
Would replacing the slow devices' hub with a USB2.0 hub make a difference?
No, because the end device is still a USB 1.1 device.
A USB hub whether internal or external will match the speed of the device which is sending the data.
So the hub will read the 1.1 speed of the USB device and match that speed to make sure the device can recieve the
information accurately. When the USB device is the same speed as the USB hub, then the hub simply repeats the singal
and does not have to match the speed.
In simple terms:
If you have a USB 1.1 device, the transfer of data between the device and the USB controller will be at 1.1 speed.
If you have a USB 2.0 device, the transfer of data between the device and the USB controller will be at 2.0 speed.
---------------------------------------------------------------------
The information above is based on the USB 2.0 specifications found on www.USB.ORG.
Role of Host PC software.
Current applications software on the PC continues to operate with USB 1.1
peripherals and is unchanged. The system software will comprehend the
increased capabilities of USB 2.0 peripherals so that it can optimize
performance. The system software will also detect sub-optimal configurations,
i.e. a USB 2.0 peripheral attached to a USB 1.1 hub, and will alert the user and
recommend a better configuration for attaching the peripherals. New
applications will be written to take advantage of the higher speed capabilities and
ease-of-use of USB 2.0 peripherals and drivers.
Role of the hub.
A USB 2.0 hub accepts high-speed transactions at the faster frame rate and
must deliver them to high-speed USB 2.0 peripherals and USB 1.1 peripherals.
This data rate matching responsibility will require some increased hub complexity
and temporary buffering of the incoming high-speed data. In the simplest case of
communicating with an attached USB 2.0 peripheral, the hub repeats the highspeed
signals on appropriate USB 2.0 upstream and downstream cables just as
a USB 1.1 hub repeats full and low-speed signals today on USB 1.1 devices.
This allows USB 2.0 peripherals to utilize the majority of USB 2.0 bandwidth.
To communicate with USB 1.1 peripherals, a USB 2.0 hub contains a mechanism
that supports the concept of matching the data rate with the capabilities of the
downstream device. In other words, the hub manages the transition of the data
rate from the high speed of the host controller to the lower speed of a USB 1.1
device. This feature of USB 2.0 hubs means that USB 1.1 devices can operate
along with USB 2.0 devices and not consume disproportionate amounts of USB
2.0 bandwidth. This new hub architecture is intended to be as simple and cost
effective as possible, and yet deliver the full capabilities of 1.1 connections.
The new USB 2.0 hub will be completely defined in the USB 2.0 specification
providing clear implementation guidelines for hub vendors and allowing a single
software driver to service USB 2.0 hub products from multiple vendors.
Role of the peripheral.
Current peripheral products do not require any changes to operate in a USB 2.0
system. Many Human Interface Devices, such as mice, keyboards and game
pads will not require the additional performance that USB 2.0 offers and will
remain as full or low speed peripherals as defined by USB 1.1.
The higher data rate of USB 2.0 will, however, open up the possibilities of
exciting new peripherals. Video-conferencing cameras will perform better with
access to higher bandwidth. Next-generation, higher-speed and higher
resolution printer and scanner devices will be enabled at the high-end. High
density storage devices such as R/W DVD, and high capacity CDROM jukeboxes
will also be enabled by USB 2.0. These devices require minor changes to the
peripheral interface, as defined in the USB 2.0 specification. Overall, the
additional cost to support USB 2.0 is expected to be minimal to the peripheral.
Both USB1.1 and USB 2.0 devices will inter-operate in a USB 2.0 system.
Summary
The USB Specification is currently at Version 1.1 and supports a wide range of
products. Many vendors are moving towards USB, drawn by its inclusion on
virtually all PC platforms and its ease-of-use. More and more types of innovative
new peripherals are taking advantage of USB, which further enhance the
available USB product portfolio.
The version 2.0 specification that is under development is an evolutionary step
that increases performance capabilities at low cost for USB peripherals in a
backwards compatible fashion. It is expected to broaden the market for new and
higher performance PC peripherals, and supercede USB 1.1 on future PCs.
---------------------------------------------------------------------
jskubick
8 Posts
0
November 23rd, 2003 16:00
OK, so in other words:
suppose a slow USB1.1 device with lots of data to transfer (say, a 2 year old scanner) is connected to a usb2 hub along with other slow peripherals (say, a mouse, a keyboard, etc), and that hub is connected to one of the D600's two USB ports.
suppose a single fast usb2 device is connected directly to the D600's other USB port.
Suppose further that the scanner is performing a scan, and transferring data to the notebook at usb1.1 speeds, and the hard drive needs to transfer data at the same time.
What you're saying is that by definition, a USB2 hub isn't supposed to think, "Hmmm. This old slow peripheral is transmitting lots of data and taking a long time to do it. My upstream connection is a lot faster, though, so instead of just blindly soaking up all the upstream bandwidth while this slow peripheral is taking its sweet time and making everybody else who needs access to the bus wait, I'll just buffer it for a few milliseconds, then relay it on to its final destination at the faster rate I'm capable of. That way, if anything else needs to transfer data along the bus, it'll have more opportunities to do so because the bus won't be held up while I'm buffering the next chunk of data from this old slow peripheral.
Furthermore, both USB2 ports on the D600 share the same bus, so while the scanner is trickling data onto the bus, the hard drive will be forced to metaphorically tap its foot impatiently like someone who's in a hurry at a grocery store, stuck behind an old lady who can't make up her mind which scratch-off lottery ticket she wants to buy -- holding up the whole line of people behind her who know EXACTLY what they want in the meantime.
Right?
Oh well. I guess that makes the decision to get a cardbus firewire card a lot easier ;-)
Karell
2 Intern
•
2.5K Posts
0
November 25th, 2003 13:00
The USB controller will split up the bandwith to accomidate both devices.
But, the USB HUB will not buffer the USB 1.1 signal to make it faster.
The signal must stay at the speed of the USB device which is sending it, in order for that
device not to get confused. When the USB hub buffers the data, it buffers it to match the
speed of the USB device, not to increase the speed.
So, the USB hub will simply repeat a signal it gets from a USB 2.0 device.
But, the hub will buffer the signal from a USB 1.1 device to make sure it is kept at a constant USB 1.1 speed.