On Tue, 22 Dec 1998 08:03:03 -0800, "Shawn Wright" <swright@xxxxxxxxxxxxxxx>
jammed all night, and by sunrise was overheard remarking:
> On 22 Dec 98, at 7:31, Rand E. Tomcala wrote:
> > Shawn Wright wrote:
> > In essence is says, capable of parallel and USB operation, for best
> > performance use parallel
> > port.
The high performance parallel port on the PC can hit rates up to 16Mb/s
or so, but usually only if you run it in ISA DMA mode, which virtually
no one does (because you have to allocate an ISA DMA channel, which is a
rare resource). Each USB port can run at rates up to 12Mb/s, and it's
always run as a PCI-based bus mastered cycle, more efficient system-wise,
but somewhat slower. By contrast, standard 10-Base-T Ethernet is 10Mb/s,
RS-422 (Mac serial) is run at 1Mb/s or less, RS-232 usually peaks out at
under 0.100Mb/s, etc.
> > I think that USB is probibly a "dumbed down" consumer gadget for the
> > hammer handed who wouldn't know (or appreciate) good performance if it
> > was explained.
> That was my suspicion as well - it appears to be the "APS" of interface
> standards.
Not really (either of these). USB was designed, and ok -- not perfectly,
but not that bad either -- as a replacement for all of the stupid I/O
ports on the back of the PC: keyboard, mouse, serial, parallel. It is
not even close to a replacement for SCSI, nor was it intended to be.
After all, if you had to put a SCSI port in every mouse, you would find
the price of mice going up by at least $30-$40 (some of that is for the
separate power supply the mouse would need, SCSI isn't exactly a
low-power technology).
> But I note that the HP scanner (I think it's the 6200 and 6250)
> come with USB and SCSI, but do not supply a SCSI card or cable, implying
> that it should work with USB.
Even SCSI-1 runs at up to 5-6MB/s (that's 40-48Mb/s). For things like
scanners that can actually go faster with a faster port, SCSI makes
sense. Actually, there aren't all that many things that cross the
boundaries. If scanners were any faster, no one would have put them on
parallel or USB ports, but any slower, they wouldn't have bothered with
SCSI. It's kind of a grey area. Otherwise, printers, floppy-like drives,
mice, tablets, etc. all should be just fine for USB (well, if you have a
print buffer, put it on a fast network or SCSI).
The advantages of USB are many. It's actually a tiered star network of
sorts, so it supports hubs that allow you add an incredible number of
devices. It supports isochronous (time-safe) transfers, so you can run
audio and MIDI over it (MIDI makes far more sense, it's kind of stupid
to suck up all that USB bandwidth for audio). It's fully auto-configuring,
the PC can detect what's there, and in fact, you can hot-plug anything
(for example, a digital camera), safely too, since it uses a phone-style
connector.
> And I haven't heard of any using a USB device with NT, so I suspect that
> would be a hassle as well.
Microsoft has an "interesting" policy these days of using new techologies
as a lever to force OS upgrades that you might not otherwise need. USB
is one of these -- it gets lip service support (keyboards, mainly) in
Windows 95 OSR2.1, but you need Windows 98 or (eventually) Windows 2000
(what used to be called Windows NT 5.0) for full support.
--
Dave Haynie | V.P. Technology, Met@box Infonet, AG | http://www.metabox.de
Be Dev #2024 | NB851 Powered! | Amiga 2000, 3000, 4000, PIOS One
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