Larry/Dean,
You're explanation is reasonable. Don't knock yourself so much!
Actually, a IDE cable can handle two devices, as you state. One (probably
your disk) is known as the master device, the other (probably your CD) known
as the slave. Some of the PCs I have, at BIOS time, actually tell you which
devices are master and slave.
The real physical problem for CD-R drives (or even CD drives playing
games) is that the master blocks the slave. Anytime the system wants to
access disk (say looking at swap space) that access takes priority on the
cable over anything going on with the CD. This is what causes problems.
To get around this problem, Intel introduced dual IDE controllers years
ago in their chipsets. Normal configuration was for one controller to talk
to the disk, and the other controller to talk to the CD. Both drives (disk
and CD) can now be masters. This gets around that problem very nicely. There
is however one last issue...
I found out a few months ago that Linux takes a default stance of not
enabling DMA on the IDE controllers. This lowers disk throughput a lot. For
instance, on my Athlon 750, talking to an UltraDMA disk drive, I measured
about 3MB/S disk access as the machine was set up after Linux install.
Enabling DMA pushed that up to just shy of 30MB/S! Prior to enabling DMA I
was not able to capture 1394 video in this system reliably. After enabling,
I don't drop frames anymore.
CAVEAT - READ THE HOWTO'S - THERE MAY BE REASONS THAT YOU DO OR DO NOT
WANT TO TURN ON DMA ON YOUR GIVEN SYSTEM! I TAKE NO RESPONSIBILITY FOR WHAT
MIGHT HAPPEN. It has, however, been completely reliable for me on this one
machine.
I am NOT at all familiar with laptop architectures these days, but I have
no reason to believe that these same issues would not effect those machines
also. Problem is it's a lot harder to look inside and see if the drive and
CD are on the same cable...
Mark
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Larry
Marshall
Sent: Monday, January 29, 2001 4:05 AM
To: [EMAIL PROTECTED]
Subject: Re: [Win4Lin-users] Re: Problems installing Microsoft Office
2000 and Project 2000
> 15 minutes or so. I've never understood why this behaviour. I just
> assumed that win4lin/linux pair was doing something nasty with the CD
> reader. Anyone care to explain it to IDE ignoramus.
As long as you don't mind the explanation coming from another IDE
ignoramous. Actually this is a problem, in a milder state, that
people experience under native Windows when they start writing CDs,
which is a data flow critical process where it can be seen.
An ide controller typically has two channels and each channel can
service two devices. So, when you plug in a hard drive you connect a
cable from the controller to the drive. When you plug in a second
device (a CD device) you just plug it onto the same cable the HD is
connected two.
These controllers have some difficulties providing data flow from one
device to the other on the same channel. Normally this isn't a
problem as the flow is buffered and short little burps are handled
without problem. When writing to a CD writer, however, it just can't
handle those burps as its buffer empties and you get a bad CD
created. It's actually recommended under Windows that you install
your CD writer on one channel and devices you're going to write from
on the other.
Under Linux this hasn't been a problem either but something got a bit
bugged in v7.2 of LM and this streaming (from devices on the same
channel) tends to fail. Until the bug is fixed the solution seems to
be to read from one channel and write to the other. I don't know of
anyone who had this problem prior to 7.2 but it's a problem now.
Hope my attempt at a non-technical explanation helps.
Cheers --- Larry
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