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