Xref: utzoo comp.protocols.nfs:1948 comp.arch:21424 Newsgroups: comp.protocols.nfs,comp.arch Path: utzoo!henry From: henry@zoo.toronto.edu (Henry Spencer) Subject: Re: Incremental sync()s and using disk idle time Message-ID: <1991Mar13.195708.28678@zoo.toronto.edu> Date: Wed, 13 Mar 1991 19:57:08 GMT References: <10773@dog.ee.lbl.gov> <3236@crdos1.crd.ge.COM> <1991Mar12.194704.17859@zoo.toronto.edu> Organization: U of Toronto Zoology In article zeeff@b-tech.ann-arbor.mi.us (Jon Zeeff) writes: > ...You >can't get much main CPU for the couple of dollars more it costs to >have smart(er) serial ports (which can provide significant performance >increases). What do you mean by "smart(er)"? If you just mean throwing in some FIFOs to ease latency requirements and make it possible to move than one byte per interrupt, I agree. I was assuming that the base for discussion was dumb i/o devices, not brain-damaged ones. If you mean DMA, that does *not* cost a mere "couple of dollars more" if it's the first DMA device on your system (or, for that matter, if it's the second), and it can actually hurt performance. (As a case in point, the DMA on the LANCE Ethernet chip ties up your memory far longer than data transfers by a modern CPU would.) >Same with smart keyboards, smart graphics controllers, smart terminals, etc. I'm not at all sure what you mean by "smart keyboards"; if you mean having a keyboard encoder chip to do the actual key-scanning, that does not require any form of "smartness" -- see comments above on dumb vs. brain-damaged. Keyboards did that long before keyboards had micros in them. The micros replaced dedicated keyboard encoders because they were cheaper and a bit more flexible, not because they added useful "smartness". "Smart" graphics controllers are useful only if they actually bring specialized hardware resources into the graphics operations. All too many "smart" graphics controllers are slower and less flexible than doing it yourself in software. Just *talking* to them to tell them what you want to do can take more time than doing it yourself. (This is a particularly common vice of "smart" devices.) "Smart" terminals are useful only if they are programmable. >Smart hardware is usually quite effective for small simple jobs. Small simple jobs don't need smart hardware. -- "But this *is* the simplified version | Henry Spencer @ U of Toronto Zoology for the general public." -S. Harris | henry@zoo.toronto.edu utzoo!henry