Very Computer

I am running kernel 2.0.17 on a box with an Adaptec 2940 controller,
which supports a hard disk and a CD-ROM (Sony CD-76S). The firmware
setup for both the hd and the CD allows them to negotiate synchronous
communication at the highest supported speed - 10 Mb/s.  However, the
aic7xxx driver reports that the CD is only being run at 5 Mb/s. The
hd successfully negotiates the higher speed.

I glanced at the aic7xxx.c code, and it appears that the CD must not
be requesting the 10 Mb/s speed.  Is this the case, or is the driver
somehow set up to reject 10 Mb/s negotiation from CD's?

--
## Jeremy Buhler * peace through superior algorithms * U. Washington ##

: I am running kernel 2.0.17 on a box with an Adaptec 2940 controller,
: which supports a hard disk and a CD-ROM (Sony CD-76S). The firmware
: setup for both the hd and the CD allows them to negotiate synchronous
: communication at the highest supported speed - 10 Mb/s.  However, the
: aic7xxx driver reports that the CD is only being run at 5 Mb/s. The
: hd successfully negotiates the higher speed.

: I glanced at the aic7xxx.c code, and it appears that the CD must not
: be requesting the 10 Mb/s speed.  Is this the case, or is the driver
: somehow set up to reject 10 Mb/s negotiation from CD's?

Why are you interested in getting the CD to run at 10MB/sec?  Even an 8x CD
is only 1.2MB/sec.

I suspect that the CD knows this, and doesn't bother trying to negotiate
to more than 5MB/sec.

        Stu

RT>: I glanced at the aic7xxx.c code, and it appears that the CD must not
  >: be requesting the 10 Mb/s speed.  Is this the case, or is the driver
  >: somehow set up to reject 10 Mb/s negotiation from CD's?

RT>Why are you interested in getting the CD to run at 10MB/sec?  Even an 8x CD
  >is only 1.2MB/sec.

RT>I suspect that the CD knows this, and doesn't bother trying to negotiate
  >to more than 5MB/sec.

One off the good things using SCSI is that You can use drives with
different speeds on the same bus.

My CD-rom runs at 4.4 MB/s I think, and the disk at 10.0 MB/s.
My Adaptec supports up to 20MB/s.

If You want Your drive to run at eg. 20MB/s You must buy drives that
supports 16bit SCSI (SCSI-2 Wide).

There is noone making CD's that run at 10, 20 or 40 MB/s. There is no
reason for it, and noone want to pay for it.

The only systems that have any need for 20MB/s drives or more are BIG
file-servers and some special purpose workstations.

Remember, that You can't buy any normal drive that cat deliver more
then about 5MB/s, and at that speed they cost $$$$$$$$$$$$.
.
1 Regards Johnny Oestergaard ?

oRime  : ->1117                     o
?

 * 1st 2.00 #589 * Silence is a heavy stone.

SO, all you have to do is find a 67 X CD rom, and you're home free!  Too bad
that 12 X is currently the fastest.

The SCSI speed is the hardware interface speed!

[stuff about not getting CD to negotiate at 10 Mb/s]

Thanks for the explanatory responses.  It would seem that the Adaptec
BIOS doesn't bother asking each device what speed it is willing to
negotiate before showing the "Max Allowed Negotiation Speed".

--
## Jeremy Buhler * peace through superior algorithms * U. Washington ##

: >: I am running kernel 2.0.17 on a box with an Adaptec 2940 controller,
: >: which supports a hard disk and a CD-ROM (Sony CD-76S). The firmware
: >: setup for both the hd and the CD allows them to negotiate synchronous
: >: communication at the highest supported speed - 10 Mb/s.  However, the
: >: aic7xxx driver reports that the CD is only being run at 5 Mb/s. The
: >: hd successfully negotiates the higher speed.
: >
: >: I glanced at the aic7xxx.c code, and it appears that the CD must not
: >: be requesting the 10 Mb/s speed.  Is this the case, or is the driver
: >: somehow set up to reject 10 Mb/s negotiation from CD's?
: >
: >Why are you interested in getting the CD to run at 10MB/sec?  Even an 8x CD
: >is only 1.2MB/sec.
: >
: >I suspect that the CD knows this, and doesn't bother trying to negotiate
: >to more than 5MB/sec.
: >
: >  Stu
:
: CD speed is 150KBps!
: 2X = 300KBps
: 4X = 600KBps
: 6X = 900KBps
: 8X =1200KBps
: 10X=1500KBps
: 12X=1800KBps
: 67X=10MBps
:
: SO, all you have to do is find a 67 X CD rom, and you're home free!  Too bad
: that 12 X is currently the fastest.
:
: The SCSI speed is the hardware interface speed!

Actually there are 20 & 30X CD-roms, but they start at around $1000 and are
designed for servers...

--
 _/_/_/_/  _/        _/_/_/_/   T Jones

  _/     _/        _/  _/       NCSU - Department of Computer Science
 _/     _/_/_/_/  _/_/_/        http://krusty.rh.ncsu.edu/~tavaris

[JOHNNY OESTERGAARD]

|   Remember, that You can't buy any normal drive that cat deliver more
|   then about 5MB/s, and at that speed they cost $$$$$$$$$$$$.

Sure you can. I have measured the Seagate Barracuda 4 GByte at 6.8 MByte/s
sustained read speed on the outer parts of the disk (100 MByte size files),
and 5.76 MByte/s sustained over the whole disk. The Quantum Atlas 4 GByte
is supposed to be even faster...

(Yes, I know these drives are not the cheapest - but I'd still classify
them as normal drives :-)