Strange SCSI behaviour - maybe missing terminator?!?

[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

[danbeaver]

Yeah, what Zac67 said, kinda

[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."

[danbeaver]

Zac, this is unconditional love!

[danbeaver]

Sorry,

Links are problematic on the iPhone

[danbeaver]

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

[danbeaver]

Yes, but with "P&P" it works out to the same 5 USD range. Those are the ones I use( I like the glowing LED to tell me it is working.

[danbeaver]

Put an active, wide Terminator on both ends of the cable. The one I picked out with the glowing LED has "Termination Power" and thus is "Active" or there would be no power to make the LED glow. No reason to invoke, "Night and Fog" in this (Nacht und Nebel).

[danbeaver]

To Mechy

So the internal chip in the active terminator works without any electrical power like a resistor?  It attempts to normalize the bus signal with an un-powered circuit?  Then what is the termination power used for?

[danbeaver]

Well that clears up the Active vs Passive question

[danbeaver]

JF, I know you didn't ask, so take this as unsolicited info:  the Acard 7720UW (100 USD) will allow a wide-to-IDE conversion for a new DVD-RW drive at full 2012 speed on your CSPPC bus and white ones to match your Amiga are available.

[danbeaver]

Again, nothing in this post will solve your issue, but since the last "unit" on the bus/chain is designated by its ID number and the controller wants to know the last device and last unit number, I have always felt that it should be a drive where this is recorded in its RDB; so I use a HDD there and a CD earlier.

[danbeaver]

It appears to me before booting the SCSI controller scans the entire bus querying each ID (and LUN) before it does any booting. Also whenever I change a device (CF Card added or removed at end of chain -- something I no longer do) when I go to HDToolBox or Media Toolbox I get a "need to update drive" request dealing with Last ID / LUN. From this I inferred that the controller wants to be able to write this info into the RDB or someplace on the drive; hence a CDROM would have no place to write this.

In addition how can an active terminator circuit "actively dampen" a signal without a power supply?  A resistor uses the power of the signal itself to reduce that signals amount of voltage, but a circuit that attends to do a proper reduction of a signal voltage should itself be powered. If so, how can it do that without, lets say for the sake of argument, without termination power. If it does so with another power source, what is then the termination power used for?  I'm not an electrical engineer and I think in terms of digital rather than analogue, but a simple transistor setup to dampen an excessive signal voltage still needs a separate power supply, or is there another way around this?