Re: CSPPC SCSI hangs

["Georges Heinesch" <ghmlist%attglobal.net@localhost>]

Quoting Ignatios Souvatzis (17-May-00 07:41:57):

>> It doesn't when using the CSPPC SCSI with NetBSD, but with AmigaOS,
>> it works fine. Is that what you meant ... ?

> No... I meant "it doesn't with AmigaOS". You told:

>> >> The only thing the Viking doesn't like so much is sync transfer.
>> >> Hence, it's diabled in my AmigaOS CSPPC bootmenu.

> which indicates that something is wrong with timing on the cable.
> at non-sync the data rate is always < 5 MHz. When sync is enabled,
> the data rate on the '770 can be as high as 20 MHz (when the disk
> agrees to that.

Yep, you are right. With sync, it also creates problems with AmigaOS.

>> > This indicates that either:
>> > a) scsi termination is wrong
>> > b) cable is wrong
>> > c) disk firmware has a bug
>> > d) disk driver in operating system has a bug
>> 
>> > As you have problems with the AmigaOS driver as well with NetBSD,
>> > I suspect it is not d).
>> 
>> I was fiddeling around with the SCSI UW termination for quite a
>> long time and managed to get some very deep into it (I did not
>> volonteer ;). I am pretty sure that the termination is fine. Here
>> the system:
>> 
>> Viking UW ---/UW/--- CSPPC ---/adapter/--- streamer ---scanner
>> 
>> 1. The Viking is actively terminated (jumper).
>> 2. The Scanner (HP 6200C) is actively terminated (automatic).

> Automatic? ugh. Hope this works. Although I must confess that the
> only auto-terminating device that I've seen does work, indeed. (I
> don't want to know what happens when two devices are
> auto-terminating...)

I agress that I reallly prefer to terminate the last device myself,
but this HP 6200C scanner gives me no choice!

>> 3. ---: normal SCSI cable.
>> 4. ---/UW/--- UW cable.
>> 5. The adapter actively terminates the 8 data bits!

> The 8 upper data bits, I guess? Then termination should be ok.

Right. Ok!

>> What can be wrong here?

> First guess: external cable length. SCSI length at Ultra speeds is
> limited. I looked it up... for non-differential busses:

> speed     devices     length      active termination
> <=  5 Mhz *       <= 6.0 m    allowed
> <= 10 MHz *       <= 3.0 m    suggested
> <= 20 MHz *       <= 1.5 m    required
> <= 20 MHz <= 4        <= 3 m      required

Total cable length is <3m and everything is actively terminated.

> Additional restrictions:
> - no "stubs" (bus to device) connections of more than
>   10 cm (including onboard distance from connector to SCSI chip).
> - devices must be 30 cm or more apart.

The 30cm are not always respected here. The CD-REOm and CD-RW are 10
cm apart.

> The host adapter counts as a device in the table above!
> The full cable length counts, including the internal part of the
> cable!

> As an experiment, you could terminate the scsi chain at the
> streamer,  disconnecting the scanner. Well, measuring the cables 

Even when I disconnect all extternal devices and terminate the plug
right after it exits the computer, the Vining doesn't like sync.
Hence, it has nothing to do with the external devices.

> Also, you can try forcing the disk to non-sync, with the -I option
> (see  my other message or "man boot".) as a workaround.

This works!

> But if its a
> cable problem you should rather hunt it down... you didn't buy an
> Ultra Wide disk just to not use 75% of the transfer speed, right?

Correct. But I suspect that the CSPPC timing problem I mentioned in
another mail, creates all that SCSI problem. The DMACs and RAMSEYs
were changed already multiple times. Phase5 knew about the timing
problems, but they never admitted it. I collected many reports from at
least 30 other CSPPC/A3000 users having *identical* timing problems!

> Also, if it's a driver bug, we should hunt it down, too, of course.
> I don't know Michael Hitch's setup, so I don't know wether he has
> multiple devices connected; I only have one disk on the UW bus, and
> connected an old disk and (occasionally) an external MO or scanner
> to the motherboard SCSI.

I believe it's the timing problem. You should also know that sync
works fine until I backup the Vinking to the streamer. In those cases
(high data flow) the sync even crashes the computer. This doesn't
always happen, nor can it be provocated, but it happens randomly.

I should add that the Amiga doesn't even boot up when a CD is inserted
into the CD-ROM (Plextor PX-32TSi) or the CD-RW (Plextor PX-W124TSi)
when sync is on on either of those 2 devices.

-- 
Cu  Georges Heinesch, Luxembourg
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