> A single multi-port USB to serial converter would address this nicely,
> but we have evaluated about a dozen of them, and while all they work
> perfectly in Windows, they are either unsupported in Linux at all,
> or horribly broken (like dropping a byte every couple of hours).
> It is an embarrassing shame. I wish our company had the resources
> to sponsor somebody to fix that.
Do they _really_ work perfectly in Windows? In my experience, cheap serial converters are prone to dropping a byte now and then, and when I searched online it turned out that it was hardware not drivers -- Windows users would experience the same problem given the same level of usage and attention to detail (it just happens a lot less often, because there are more of us Linux developers making heavy use of serial ports).
Sorry I can't find an actual reference explaining the hardware issue on a common PLX usb-serial chip; there is no sufficient replacement yet for the recently-discontinued Google Linux search :`-(
I agree that keyspan did not have these problems, but they were significantly more expensive and seem to have lost out to the even cheaper but somewhat flaky adapters...
If there are current multi-port adapters that really do have higher quality chips in them (i.e. like keyspan rather than PLX) but lack Linux drivers, then somebody should get in touch with the Linux Driver Project and donate such an adapter! http://www.linuxdriverproject.org/