On Tue, 2002-05-14 at 23:19, Sridhar Dhanapalan wrote: > > > > Ahhh...Carroll, my friend. :) That is the beauty part. If indeed you do > > contemplate an upgrade, all you need do is get a usb serial/parallel > > adapter for a modest sum, and presto, your printer and modem are back in > > business. In addition, having done that you can do as I did and use > > IRQ's 7, 3, and 4 for things other than being tied to onerous dated and > > obsoleted onboard ports. Obsoleted in the sense that their functions > > are now duplicated on a less resource intensive external bus. > > How is the CPU usage of USB compared to the 'legacy' ports (serial, parallel, > PS/2, etc.)? The legacy ports were designed for older systems, so they cannot > suck up too much juice.
It is interesting that you bring up the CPU usage aspect of USB, as I've not seen any numbers regarding that. The resource benefits I was referring to was directed towards IRQ usage, because I have a real need for extra IRQ's (and I suspect others with legacy hardware do also), so in that regard the USB bus was a real benefit. There's a lot you can do with three extra IRQ's. I am interested in CPU utilization numbers, if you've got some URL's... > I hear that USB, on the other hand, is a real pig in > this regard (no surprise that Intel supports it). If that is the case, is it > really worth using USB peripherals on a PC when legacy types would suffice? That begs the question of some numbers, does it not? Such as, what exactly is required for the device in question? (is it an isdn modem, or....) Not only that, but in order to answer your question properly you also need some performance numbers in regard to the chipset platform that is giving you the USB functionality. Quite naturally, this is going to be giving different performance results depending on which chipset platform you choose; i.e., Intel or Via. "Performance" in this context meaning both CPU utilization and USB bus throughput. > Here, I am referring to simple components that have little to gain from USB, > like keyboards and mice. I don't want my keyboard and mouse slowing down my > system :) > > -- > Sridhar Dhanapalan I've never been an advocate of moving primary user IO off the legacy ports. You are removing redundancy and putting all your eggs in one basket, cause if the USB bus goes you lose it all. I know you've got a little tongue in cheek here with the mouse/keyboard thing, but just for the heck of it I'll run the numbers on it. There's not much of a chance that a 1200 bits/sec mouse serial stream and a character stream from some human hands at the macro level can influence a bus that's been benched at up to 5.7 MB/sec (BTW, the USB bus has been *marketed* as a 12 MB/sec bus. 5.7 is the best I've seen in RL, tho). So you've got a mouse that communicates at 150 bytes/sec on a bus that has been RL evaluated at 5.7 Megabytes/sec; that's 38,000 times more bandwidth than the mouse requires. This is an invalid evaluation however, because I still don't know how fast you can type. ;) L8r, LX -- 같같같같같같같같같같같같같같같같같같같같같같같같같� Kernel 2.4.8-26mdk Mandrake Linux 8.1 Enlightenment 0.16.5 Evolution 1.02 Registered Linux User #268899 http://counter.li.org/ 같같같같같같같같같같같같같같같같같같같같같같같같같�
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