I found some info here that might apply:

http://www.scsifaq.org/scsi_quick_start.html#_Hlk410547597

===============================================================================
QUESTION: Will attaching a SCSI-1 device to my SCSI-2 bus hurt its
performance? 

ANSWER From: Gary Field (scsifaq at engineer.com) 


Attaching a SCSI-1 device to a system with a SCSI-2 host adapter and
several SCSI-2 devices already attached will not hurt over-all
performance significantly unless it doesn't handle disconnect/reconnect
well. This assumes that the host adapter keeps track of
protocol options separately for each target device. Some people have the
idea that attaching a SCSI-1 device to a SCSI-2 bus will cause
the entire bus to run at SCSI-1 speeds. This is not true. 

Table of Contents 

QUESTION: Can I connect a SCSI-3 disk to my SCSI-1 host adapter? 

Can I connect a SCSI-2 CDROM to a SCSI-3 host adapter? 

Can I connect a Narrow SCSI2 disk to a WIDE SCSI3 host adapter? 

ANSWER From: Gary Field (scsifaq at engineer.com) 


Questions of this nature really cannot be answered in a useful way.
There are so many aspects and options to each of the SCSI
standards, you need to be much more specific about what devices and
adapters you're interested in connecting. Most of the time the
best thing to do is just try it! Most combinations will work, but if
you're considering a purchase and looking for a guarantee from "The
Net", forget it. 

The issue is further complicated by the fact that vendors like to latch
onto the latest acronyms before they even know what's involved.
For example SCSI3 is not approved yet, but vendors are already saying
their devices are SCSI3 compatible. Since there is no standards
compliance testing organization, they can pretty much say what they
want. 

If you buy a high end host adapter (probably called SCSI3 :-) ) from a
reputable vendor, and it has enough control over the various
options (like synch xfer rate 5,10,20,40 mega-xfers/sec and the ability
to disable WIDE or FAST/Ultra negotiation), and you carefully
think out what devices you connect to it (all WIDE devices nearest the
host adapter end of the bus etc.), and you are careful to properly
terminate not only both ends, but both halves (upper byte and lower
byte) of the bus, and none of the older devices you might already
have (like a Panasonic CDROM) do anything stupid (like not handle the
WIDE negotiation message without hanging) then it will all work
fine. :-) 

Even though a host adapter may be called SCSI3 doesn't mean it can
enable or disable each optional feature, yet this is vital for
supporting older devices. 

To make matters worse, you won't know which older devices do some of the
stupid things unless you know someone who's been bitten
already. Your best bet is to look for good deals on name brand devices
and adapters and before you buy, ask in comp.periphs.scsi
whether anyone has tried the combination you're considering. It's also
important to buy from a well known vendor with reasonable
return policies. 

If you're looking at buying a Vendorxyz spiffydisk which claims to be
SCSI-3 compatible and you have a Seagate ST-01 host adapter
and you want to know if anyone else has tried this combination, then
that's exactly what you should ask. 

In general, most SCSI devices and adapters made less than 4 years apart
will probably work together, but without specific information
about exactly which devices there's no assurance of it. There's also the
potential for poor performance even if it does work. 

Table of Contents 

QUESTION: Can I connect a WIDE device to my narrow SCSI host adapter? 
QUESTION: Can I connect a narrow device to my WIDE SCSI host adapter? 

ANSWER FROM: Gary Field (scsifaq at engineer.com) 
Updated: June, 2000 


Yes, you just need an appropriate adapter. Most WIDE devices use the 68
pin "P" connector so you need a 68 pin to 50 pin adapter. 
You do need to make sure that both the upper byte and lower byte of the
bus will be properly terminated though. Some adapters 
provide Hi-9  terminators, others do not. If the wiring adapter is
placed right at the SCSI host adapter, you can usually configure the 
host adapter's on-board terminators to only terminate the high byte. You
need to be clear on what type of connectors are present 
where you want to do the conversion. You also need to plan your bus so
that there won't be any narrow cable between any of the 
WIDE devices. 
Certain host adapters with auto-termination make the assumption that
when the low byte is terminated the high byte is also. When 
using WIDE/narrow adapters this assumption is not valid. Another purpose
served by the hi-9 terminator is supplying pull-up 
current to the upper data lines which would otherwise be left floating. 

Special note for LVD drives: 

It is recommended that if you connect a WIDE LVD drive to a narrow bus
that you use a 68 to 50 pin adapter which has high byte 
termination. It may seem that the termination wouldn't be needed in this
case because the bus is narrow. However, the drive needs to 
have those signals "pulled up" (logically negated), to avoid the
floating signals from confusing it. 

If for some reason you attach a WIDE device to a WIDE host adapter using
a narrow cable, you must be sure to disable WIDE 
negotiation in the host adapter BIOS or the device will hang when it is
accessed. 

One further caveat is that if narrow devices are attached to a WIDE
adapter, the adapter's ID must be between 0 and 7 because 
narrow devices would not be able to see it if the ID was any higher than
7. 
===============================================================================

Nate Carlson wrote:
> 
> On Thu, 31 Aug 2000 Nick.T.Reinking at supervalu.com wrote:
> > I've heard really good things about Teac CD-Rs and CD-ROMs
> > if you're trying to do weird things (overburn disks, bypass copy
> > protection, copy PSX disks, etc.)
> >
> > As far as the UW thing goes, you should be able to get an
> > 68pin->50pin connector for a Kenwood, and run it right up there
> > with the rest of your UW devices.  ;P
> >
> > Nick Reinking
> 
> I've seen cases where when you use a converter on one device on your UW
> scsi chain, you also have to disable wide negotiation for the rest of them
> for anything to work.. not good.  :)
> 
> --
> Nate Carlson <natecars at real-time.com>   | Phone : (952)943-8700
> http://www.real-time.com                | Fax   : (952)943-8500
> 
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-- 
Troy Johnson   mailto:john1536 at tc.umn.edu   http://umn.edu/~john1536/
Still, if you will not fight for the right when you can easily
win without bloodshed, if you will not fight when your victory
will be sure and not so costly, you may come to the moment when
you will have to fight with all the odds against you and only a
precarious chance for survival. There may be a worse case.  You
may have to fight when there is no chance of victory, because it
is better to perish than to live as slaves.
	--Winston Churchill

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