does aha2940UW work with Seagate LVD disks?

[Steve Brueggeman]

On Tue, 2 Dec 1997 15:49:11 -0200, you wrote:

>Seagate announces an "ultra2" interface supposedly capable of 80MHz
>transfer rates, the low-voltage-differential. Which aha will work with
>these disks? Must it be a differential board?
>
>Carlos

I believe that all Seagate ultra2 drives support both Single Ended, and Low
Voltage Differential.  The drives switch automatically according to the
diffsense line.  If diffsense is grounded, the drives go into Single Ended mode,
so the drives will 'work' with an Adaptec AHA 2940(UW), but only in Single Ended
mode.  Note also, that all devices on the SCSI bus MUST be in the same linemode,
so if even one device is Single Ended, all devices will be in Single Ended mode.

But, Single Ended mode does not support 40Mhz transfers (80MB/sec on a wide
interface).  Single Ended mode only supports Ultra-1 (20Mhz or 80MB/sec on wide
interfaces).  To get 40Mhz transfers, you need a host adapter that has LVD
drivers.

I just checked out adaptec's website
(http://www.adaptec.com/deskpcon/aha2940u2w.html)
Looks like they have a board that supports both LVD and Single Ended, like the
Seagate drives do.  No mention about availability.

The chip they are using appears to be an AIC7890 and an AIC3860.  I have no idea
if this is currently supported under Linux or not.

Steve Brueggeman.