ez-scsi speed settings and aic7890

[Mike Bilow]

Doug Ledford wrote in a message to Mike Bilow:

>   Vendor: RICOH     Model: RO-1420C          Rev: 1.62
>   Type:   CD-ROM                             ANSI SCSI revision: 02
> Detected scsi CD-ROM sr1 at scsi0, channel 0, id 4, lun 0

 DL> This one didn't negotiate any synchronous transfer speed,
 DL> but that's expected on the Ricoh devices.  They don't
 DL> support sync operation. 

> (scsi0:0:6:0) Synchronous at 80.0 Mbyte/sec, offset 31.
>   Vendor: QUANTUM   Model: VIKING II 4.5WLS  Rev: 4110
>   Type:   Direct-Access                      ANSI SCSI revision: 02
> Detected scsi disk sda at scsi0, channel 0, id 6, lun 0

 DL> 80MByte/s on the drive, good.
* * *
 DL> There is nothing wrong with that configuration.  The problem
 DL> appears to be memory corruption.  When the CD-ROM is run at
 DL> full speed under NT along side the Ultra2 disk, you get
 DL> corruption as well.  Because the linux ext2 filesystem is in
 DL> general faster than NT's filesystem, you see the same memory
 DL> corruption with lower speeds on the CD-ROM.  Basically,
 DL> linux is faster and that makes it break with lower transfer
 DL> speeds.  I would suggest you try swapping out the RAM and/or
 DL> CPU to see if the problem goes away.

I would like to take a flyer on this one, but I disagree with Doug's guess
about memory corruption.  I agree that the driver is not at fault, of course.

My guess is that the CD-ROM drive is bad.  Running in the presence of an 80MB/s
Ultra2 device might confuse it.  If you can, I suggest that swapping the CD-ROM
drive with, frankly, a better brand -- say, Toshiba -- might solve your
problem.  I would go so far as to say that, in my opinion, it is unlikely that
Doug's suggestion about swapping RAM and CPU will have any effect.

You could probably stabilize the system by limiting the hard drive data rate,
but that is not a real solution.  Overterminating the SCSI bus, so that
termination on the controller (which must be in the middle on your system) is
enabled in addition to each end of the bus could help, too, although this is
certainly not a recommended long term solution.
 
-- Mike




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