Followup on 274xT Adaptec

[Doug Ledford]

--------
> Ok, per Doug's request I hacked up the driver to panic just before
> scanning Chan. A.  Here's what transpires:

Thanks :)

> 
> aic7xxx: <Adaptec AHA-274X SCSI host adapter> at EISA 2
> aic7xxx: BIOS enabled, IO Port 0x2c00, IRQ11 (level sensitive) Rev <= C
> aic7xxx: Extended translation disabled.
> aic7xxx: Twin Channel, A SCSI ID 7, B SCSI ID 7, 4/4 SCBs, Qfull 4, \
> 		QMask 0x7

This is what I wanted to see.  We are setting the p->bus_type = AIC_TWIN 
prior to our call to loadseq();

> aic7xxx: Downloading sequencer code... 378 Instructions downloaded

My 2842 only downloads 369 instructions, so this looks like we are getting 
the twin channel sequencer support.

> scsi0: Adaptec AHA274X/284X/294X (EISA/VLB/PCI - Fast SCSI) 4.1/3.2
> scsi: 1 host
>   Kernel panic <6>scsi0: Scanning Channel A for devices

Justing, according the the books on these chipsets, what exact conditions 
can cause the settings of SIMODE0 and 1 to get changed, and does it matter 
if we set the conditions prior to enabling the bus drivers?  Could the fact 
that we are doing the outb(ENABLE, p->base + BCTL); after we set the SIMODE? 
registers be causing the B channel settings not to take?  Also, I wonder how 
a completely absent cable and termination would effect how the card handles 
these things.  Steve, if you go ahead and put a device on the second 
channel, does it work then?  I think I recall you saying there currently 
isn't anything on the second channel.

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