Hi there, On Wed, 17 Mar 2004 [EMAIL PROTECTED] wrote:
> Is there any way to enable DMA on an external USB drive? No. Generally speeds depend on the way you're using the discs since they're electro-mechanical things, and are 'better' at sequentially reading sectors than hopping about over the surface looking for odd bits of data (or somewhere to write it). The drives themselves cache data, so you can get better 'burst' transfer rates for small data transfers than sustained rates for large transfers. Your question isn't specific so it's difficult to know what you need to know. DMA requires that there is hardware (the DMA controller) physically wired beween the IDE controller and the memory in your box, so that the data can go direct to the memory without the CPU getting involved. USB involves the CPU a great deal for data transfers, it's designed that way. You might for example find that you can improve performance with a faster CPU but you need to ask yourself better questions before you go out buying new hardware. > If DMA can't be enabled, are there any similar methods for tuning that > would allow the same type of performance increase? Performance is limited by the USB design. USB 2.0 is faster than USB 1.x and the data rates are available in the specifications. It will never reach the speeds that you can get from fast disc arrays using DMA which can be an order of magnitude better without difficulty. You could I suppose conceive a storage system which used USB in a RAID arrangement, but I'd say that was pretty crazy. It's not what USB is for. Maybe there'll be a USB 3.x sometime... 73, Ged. ------------------------------------------------------- This SF.Net email is sponsored by: IBM Linux Tutorials Free Linux tutorial presented by Daniel Robbins, President and CEO of GenToo technologies. Learn everything from fundamentals to system administration.http://ads.osdn.com/?ad_id=1470&alloc_id=3638&op=click _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
