张韡武 <zhangweiwu <at> realss.com> writes:
> Hello. My old sparc server have a USB extension card, which provides two > USB slots at the back of the machine, driving a USB printer on Slot A. > This printer runs at heavy load. because it cannot print the documents > as fast as we need, I wish to add another printer. In most casese, we > need the two printer working together the same time rather then one > after the other. > The two USB slots provided by the USB card are both OHCI (some USB 1.x > stuff, not USB 2.0). So far it seems one single printer uses up all the > USB bandwidth (sometimes printer stop there several seconds wait for > signal). What would happen if I put another Printer there? > case A: the new printer uses the bandwidth on slot B, both run as fast > as if they were the only USB printer; > case B: the new printer share bandwidth with the old one, the result is > both printer work 1/2 fast, that is equal to not having bought another > printer at all. > Which one is true? USB is a 'multi drop' serial bus, like rs485. So if 2 devices on the same usb bus use equal bandwidth, the bandwidth available will be less than 1/2 the standards stated throughput. There is always overhead, due to negotiations and arbitration on busses and any form of shared media. Not all USB chips perform up to the usb 2.0 spefication, when robustly benchmarked. (caveat emptor). Drivers and contention for I/O to the kernel can be another common area for under optimiztion of USB. Um you cannot tell how many usb chips and what version of usb they are running by looking at the physical port. To discern more about the details of your usb hardware, ports, chips, busses and versions of usb those chips(firmware support) you need to use some commands like: lsusb and lshw. (lspci and discover) also. on one of my portables, lspci shows: <snip> 00:03.0 USB Controller: Silicon Integrated Systems [SiS] USB 1.0 Controller (rev 0f) 00:03.1 USB Controller: Silicon Integrated Systems[SiS] USB 1.0 Controller (rev 0f) 00:03.2 USB Controller: Silicon Integrated Systems [SiS] USB 1.0 Controller (rev 0f) 00:03.3 USB Controller: Silicon Integrated Systems [SiS] USB 2.0 Controller <snip> Installing the printers off of (2) separate USB busses that are indeed usb 2.0 compliant should solve your problems. You might need to use different hardware discovery commands on a sparc architecure.... hth, James -- gentoo-user@gentoo.org mailing list
