USB1.1 support?

[vanweric]

I'm trying to decide whether or not I need to support USB 1.1 / full-speed.  How do I estimate prevalence of full-speed only hosts?

The rest of my application relies on SSE3 instructions, so I guess the real question is whether or not requiring high-speed will further reduce my target pool.

[Jan Axelson]

USB 2.0 has been around for 11 years.

As to whether your customers will be using 1.1 hosts, I think it depends in part on the device's market, but in any case, I don't think the numbers are large.

To pass USB IF compliance tests, the device may need to respond to bus resets and standard requests at full speed to inform the host that the device requires high speed to perform its function.

Jan

[Bret]

It's not just USB 1 hosts you need to woory about, but also USB 1 hubs.  Numbers are probably limited there also, but they certainly aren't non-existent.  I still have several of them.

I personally think it's a bad idea to be potentially telling a customer, "You may need to buy some new hardware besides what you're getting from me or mine won't work."  Unless you're device/application simply won't work properly at a slower speed, I think you should support USB 1.  But that's just me.

[vanweric]

Thanks for the input!

When my device is plugged into a 1.1 port, the application appropriately recognizes the device and appropriately recognizes its speed.  Unfortunately, the actual protocol is too large for the packet size of 1.1 HID.  To support it, I would have to implement a way of chopping protocol packets up over multiple USB packets and re-assemble on either side.  Do-able, but non-trivial.  The resulting data-rate isn't unusably bad, but it is a noticeable degradation.

I haven't found any southbridges since 2003 that didn't support high-speed, but I have found that AMD southbridges usually have two 1.1 ports.  I think the pain threshold would be finding a chipset that supports the rest of the application (>XP SP2 and SSE3) but doesn't have any high-speed support.

[Jan Axelson]

It sounds to me like you have good reason to be high speed only.

Jan