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Mac Forum / General / Hardware / December 2005Poss to ugrade USB1 to USB2 (iMac)?
I have an iMac and an iBook, both with USB-1. I need an external DVD writer, and may soon replace ny scanner and printer. As most such peripherals are USB-2 now, (a) would they work under USB-1, (b) is it possible to upgrade these older computers to USB-2 (and if so, how)? TIA Rab > I have an iMac and an iBook, both with USB-1. I need an external DVD > writer, and may soon replace ny scanner and printer. > As most such peripherals are USB-2 now, >(a) would they work under USB-1, Yes, USB 2.0 is 'backwards compatible', so any USB 2.0 device works on a USB 1.1 port, but only at USB 1.1 speeds. > (b) is it possible to upgrade these older computers to USB-2 (and if so, > how)? Not easily. Normally you would use a USB 2.0 PCI card, but these computers do not have PCI slots.  SignatureJohan W. Elzenga johan<<at>>johanfoto.nl Editor / Photographer http://www.johanfoto.nl/ > I have an iMac and an iBook, both with USB-1. I need an external DVD > writer, and may soon replace ny scanner and printer. [quoted text clipped - 3 lines] > TIA > Rab The printer and scanner will be fine with the USB-1 ports. The USB-1 will be too slow for the DVD burner. It is possible to replace the CD drives in the iMac and iBook with DVD burners, but you have to be very careful. If you can't find a firewire external DVD burner, you can buy the internal model and a 5.25" firewire case. You can't upgrade the USB ports to USB-2. If your printer really needs more speed than USB-1, get a router and connect it via ethernet. > You can't upgrade the USB ports to USB-2. If your printer really needs > more speed than USB-1, get a router and connect it via ethernet. How would that help ?, or did you mean a router with builtin print server!! Dave >> You can't upgrade the USB ports to USB-2. If your printer really needs >> more speed than USB-1, get a router and connect it via ethernet. > > How would that help ?, or did you mean a router with builtin print server!! > > Dave Any printer that needs data faster than USB-1 probably has a network option. e.g. my postscript printer can connect via USB or using LP protocol through the ethernet. A print server (either built-into the router, or connected to a port) would also give you fast data (assuming you have a printer driver that knows about the print server). I think the gimp print drivers can handle this, but it is unlikely that USB-1 will slow your printing. > I have an iMac and an iBook, both with USB-1. I need an external DVD > writer, and may soon replace ny scanner and printer. [quoted text clipped - 3 lines] > TIA > Rab An interesting question, anyone know what the USB chipset is on the iMac? it may be possible if there is a later USB2 chip that is pin-compatible, (and yes I can replace QFP chips). The only problem then may be getting the OS to recognise the new chip. I may be getting a cheap iMac tomorrow, perhaps I can find a USB2 card with the right chips on it and perform the surgery, if so I will post the results here. Ben. > > I have an iMac and an iBook, both with USB-1. I need an external DVD > > writer, and may soon replace ny scanner and printer. [quoted text clipped - 6 lines] > An interesting question, anyone know what the USB chipset is on the > iMac? Depends on the model. > it may be possible if there is a later USB2 chip that is > pin-compatible, (and yes I can replace QFP chips). From a quick glance at the developer notes, it seems that the original iMac models (up to the last model with tray-loading CD-ROM drives) used a standard USB controller chip with OHCI-compatible registers, and it was connected directly to the PCI bus. In theory it might be possible to replace this with a later pin-compatible and register-compatible chipset, assuming EHCI is upward compatible with OHCI and there aren't any artificial speed caps on the iMac's PCI bus which would limit the throughput. Mac OS X support should be OK, but I don't know whether Open Firmware would know how to handle the USB2 controller, which might prevent it from working properly, or limit it to USB1 mode only. In later iMac models, the USB controller was integrated into the KeyLargo I/O device controller, which is an FPGA designed by Apple. By the 2001 models (last generation of iMac G3) the KeyLargo with integrated into the Pangea FPGA, which also controls the memory. Replacing USB1 with USB2 would be impossible in these models, unless there was some way to tack a separate USB2 controller onto the PCI bus. When USB2 was introduced, it was done by adding another PCI-based USB controller. Some Mac models continued to use the USB1 controller in the FPGA for some peripherals (e.g. the internal modem) while others stopped using it completely (and the USB1 controller was probably removed in an update to the FPGA). > The only problem then may be getting the OS to recognise the new chip. > I may be getting a cheap iMac tomorrow, perhaps I can find a USB2 card > with the right chips on it and perform the surgery, if so I will post > the results here. Go for it. Old iMacs aren't much use for anything else these days. :-) SignatureDavid Empson dempson@actrix.gen.nz |
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