Strange SCSI behaviour - maybe missing terminator?!?

[JohnFante]

I recently bought a A4000 with a CSPPC, CVPPC etc.

There are three HD's, two CD's and a zip drive connected to the SCSI-controller.

However I think there is a missing terminator on one end of the SCSI-chain.

I get an strange behaviour with one of the HD's when I install OS4.1 (see picture). It installs fine on one of the other HD's (not the one with the error) but my system has an tendency to lock (with only a reset as the cure) when I copy huge amount of data from one HD to another.

As far as I can see my chain is

Terminator
CSPPC
Seagate ST150176LW 0001 - 46,5GB
IBM DRHS36D 0110 - where OS4.1 is installed
CD-ROM PX-32-TS
HP35470A (ZIP)
CD-R PX-W124TS
Quantum Viking II 4,5WSE5520

I have attached a photo of the last drive (the Quantum) and as far as I can see there is no terminator after the Quatum.

Does anybody know what could be the cause of the behaviour, and do I need a proper terminator after the Quatum HD and what kind should it be?

I do not know if it is any help but SCSI-config (on 3.9) gives this:

Units:
Board 0 - Unit 1 - DRHS36D
Board 0 - Unit 2 - CD-ROM PX-32-TS
Board 0 - Unit 3 - HP35470A (ZIP)
Board 0 - Unit 4 - CD-R PX-W124TS
Board 0 - Unit 5 - ST1250176LW
Board 0 - Unit 8 - Viking II 4,5WSE5520

Thank you in advance.

[danbeaver]

Are all these guys (devices) attached the the 68-pin cable?

At least 4 of these are SCSI 1/2, the hard drives I can't tell by looking (I'm in bed typing on my iPhone with a fat white cat on my chest). Are any of the hard drives UW160/320?  These questions have nothing to do with your problem, because, YES. You near an "active, wide, LVD/SE Terminator" at the other end of the cable.

The CSPPC SCSI device can reach near 40MB/s with SCSI-3 (also known as UltraWide) supported. The SCSI 2 will slow your bus down to 10MB/s or less. The drive transfer types compatible with the SCSI 3 bus are also listed as U160 or U320; Amy may not reach those speeds, but these drives are real inexpensive off *Bay, and I've gotten 35MB/s on a windy day.

But yeah, get on the web (*Bay) and score a Terminator, and don't spend more than 10 USD for one (good ones have an LED that glows to prove its active).

[danbeaver]

Additional info:
SCSI 1: 5MB/s. 8-bit data w/ asynchronous transmission
SCSI 2: 10MB/s  8-bit data w/ synchronous transmission
SCSI 3:  Confusing, ranging from 20MB/s (50-pin) to 40 MB/s (68-pin), with speed improved by faster clock and error checking (CRC)
Wide = 16-bit data
Ultra = improved bus communication
U160/320 = MegaBits/s (not MegaBYTES/s) -- bigger numbers sound faster, but these transfers are parallel and should be referred to as bytes, leaving Bits to serial transfer
Synchronous = bytes can be sent without each bytes getting a "received signal"
CRC = cyclic redundancy check -- done on transmitted data every 8/16/32/.... Byte to assure accuracy at high transmission rates

Termination = keeps sent signal on the bus from ranging wildly with the faster the signal, the more wildly it can go; Passive is dampening using a set of resistors that can be used usually with SCSI 1/2; Active = an electrical circuit actively dampens the signal to prevent errors from fast transmission speeds. Active is ALWAYS better than passive, and is best reproduced at the cable level (my opinion).
Narrow termination = 8-bits are dampened
Wide termination = 16-bits are dampened

On a Wide cable (68-pin CSPPC) a wide terminator is needed at BOTH ends; narrow termination leave 8-bits running free and wild to represent any ole' number they wish

[Zac67]

UW-SCSI is very picky about termination quality, cable quality, device spacing(!) and cable length(!!). With >4 devices connected to the bus it runs a maximum of only 1.5 m.

Single Ended was abandoned beyond Ultra SCSI because of this. All later standards used Low Voltage Differential signaling.


The bus ends MUST be terminated actively (SE or LVD/SE) and the devices next to the ends should be supplying termpower. My guess is device spacing (any connectors added after manufacturing?), overall cable length or cable quality. Another possibility is a SCSI-2 device influencing the Ultra-SCSI transmissions. I've also seen bad wide-to-narrow adapters.

If you can't or don't want to change the cabling you can probably slow down CSPPC SCSI to Fast-Wide (20 MB/s max) in general to get rid of the problems. Another approach is to move the slower, non-Ultra devices to a separate bus (=controller).

[JohnFante]

Are all these guys (devices) attached the the 68-pin cable?

At least 4 of these are SCSI 1/2, the hard drives I can't tell by looking (I'm in bed typing on my iPhone with a fat white cat on my chest). Are any of the hard drives UW160/320?  These questions have nothing to do with your problem, because, YES. You near an "active, wide, LVD/SE Terminator" at the other end of the cable.

The CSPPC SCSI device can reach near 40MB/s with SCSI-3 (so known as UltraWide) supported. The SCSI 2 will slow you bus down to 10MB/s or less. The drive transfer types compatible with the SCSI 3 bus are also listed as U160 or U320; Amy won't reach those speeds, but these drives are real inexpensive used.

But yeah, get on the web (*Bay) and score a Terminator, and don't spend more than 10 USD for one (good ones have an LED that glows to prove its active).

Everything is connected to the same cable. Some have adapters so the cable can connect but that is that. One long chain.

Thanks for the advice on the terminator. Any specific suggestions for wich one?

[danbeaver]

Yeah, what Zac67 said, kinda

[Zac67]

The SCSI 2 will slow your bus down to 10MB/s or less.

No. The bus will arbitrate the best speed with each device separately. Slow devices may use up a lot of bus time while they're in use, slowing down faster devices, but they do not slow down the bus in general.

The only exception to this rule is when connecting an SE device (up to Ultra SCSI) to an otherwise LVD bus (U2W+), forcing the whole bus to SE mode electrically. But there's no LVD controller for the Amiga, so this doesn't count. (There's even an exception to this exception rule when using a SCSI bridge like e.g. the Adaptec 2940U2W does.)

SCSI 1: 5MB/s. 8-bit data w/ asynchronous transmission

Not entirely correct - SCSI-1 has asynchronous (~3.5 MB/s max) and synchronous mode (5 MB/s max).

U160/320 = MegaBits/s (not MegaBYTES/s)

Nonsense - it's 160 / 320 megaBYTES/s.
Our old LTO-3 drive peaks at ~120 MB/s. 320 Mb/s would only be 40 MB/s.

Another note on termination:
Passive terminators are only supported up to Fast (Wide) SCSI. Ultra (Wide) SCSI requires active termination and U2W, U160, U320 require LVD(/SE) terminators.

[danbeaver]

Yes, I like "68-pin active SCSI terminator -brand new FOX CONN" the price is right as is shipping -- free

Some places want up to 60 USD For these

Sorry Zac, you are right it is megabytes; please note it is 6am here, I've been up all night and there is a heavy animal sitting on my chest

[danbeaver]

Zac, as I said earlier, "To err is human, to forgive is unexpected."

[Zac67]

Well, maybe you should get rid of that feline hulk...

[danbeaver]

Zac, this is unconditional love!

[JohnFante]

Thank you for your help.

I think I will take the ZIP and CD-burner of the chain and get a new terminator.

Can anybody recommend any good ones that you can buy online (a link would be nice :-))?

[danbeaver]

Sorry,

Links are problematic on the iPhone

[JohnFante]

Could I use something like this?:

http://www.ebay.co.uk/itm/SCSI-3-Half-pitch-68-male-active-terminator-Ultra-Wide-/130592807947?pt=UK_Computing_Drive_Cables_Adapters&hash=item1e67f01c0b

[danbeaver]

That sounds like it will work (at over twice the price of the US eBay one)