Subject: Re: ncr hangs system
To: Ross Harvey <>
From: Thor Lancelot Simon <>
List: port-alpha
Date: 03/19/1999 12:19:13
On Thu, Mar 18, 1999 at 03:05:46PM -0800, Ross Harvey wrote:
> There are fundamental theoretical reasons why SE doesn't work well.
> If someone doesn't know what they are, and would like to know, I would be
> happy to fill them in off the list. :-) :-)
> Note that the NONE of the new low voltage interfaces even have a SE
> spec: they are ALWAYS differential.

N.B. every device I've ever seen that does the new modes falls back to
FAST-20 SE if there's any non-LVD device on the bus, including the
terminators.  So at least there's some semblance of backwards compatibility.

(You probably already knew that, but some readers might not)

One of my clients just bought a prepackaged Linux box from VA Research.
It's a very nice 2U machine with an Intel motherboard that's *supposed*
to have onboard dual-channel LVD SCSI.  Unfortunately, though the
Intel specs put a 53c896 on the board -- dual-channel Ultra2 LVD SCSI --
the board was aparrently special-ordered by VA Research with a 53c876
instead... and they won't swap out the motherboard for us.  Makes me want 
to scream.

They shipped the thing with two Quantum LVD disks, because Quantum only
*makes* LVD disks in the high-end models now.  Both are running in SE
FAST-20 16-bit mode now.  I have to buy a big RAID array for the box;
I'm going to put all LVD disks on it, put an SE host module in it (unless
CMD's LVD host module will fall back to SE), and run as short a cable from
it to the controller as I can.  I'm hoping it'll work at 40MB/sec...

Of course, that leaves me moving the two internal LVD disks onto the other
bus they helpfully provided -- which unfortunately has a *narrow* connector
on the motherboard.  Now I just have to find a *good* 68-pin to 50-pin
SE converter that actually terminates the upper 8 bits, and pray that those
disks will work not just SE, but 8-bit SE...

Gosh, life would certainly have been a lot easier if they just picked the
"best mode" and specified it.  I really have to agree with you there. :-)

Thor Lancelot Simon	                            
	"And where do all these highways go, now that we are free?"