ACSI bus... Do all hard drives need to be powered on?

[Calab]

I have a MegaFile 60 and an UltraSatan. Each works find when connected to my Atari Mega ST2. If I connect the MegaFile to the ST and the US to the Megafile and power them both up, they also work fine. If I don't power up the MegaFile, the system doesn't boot as if the US wasn't there.

ID0 = UltraSatan slot 1
ID1 = UltraSatan slot 2

ID3 = MegaFile 60

 

If I have multiple hard drives on the ACSI bus, do the middle devices need to be turned on to see the devices at the end of the bus?

[TGB1718]

It's probably not working as the device that's not powered still has it's interface with passive components

i.e. terminators that are not powered, so may be draining the signals internally, the source from the ST can

only push a certain amount of milli-amps through the interface, so I guess it's being overloaded.

[ParanoidLittleMan]

Of course that need to be powered on. And rule is to power on first peripheral/hard disk, and computer when all other is powered.

Additionally, it is highly recommended to attach only what will be used in oncoming session. Machines are very old, and it's best to not load output lines without real need.

For instance, I don't connect even floppy drive to my Ataris, except rare cases when I need some test what involves real floppies.

[+DarkLord]

It really just depends.

 

On the system that powers my BBS, the SCSI chain is like this:

 

Mega ST4 --> SyQuest EZ-135 --> 4gig Seagate Hard drive --> 2x CD-ROM/Writer.

 

The ICD Link 2 adapter is attached to the EZ-135.

 

The SyQuest EZ-135 is turned off. I only turn it on to do backups and file copies.

 

Of course, as mentioned above, this is a SCSI setup, not ACSI.

 

In your case, if something wasn't working like it's supposed to, I'd turn it on.

 

[ijor]

In the exact example you describe, the Megafile being first in the chain, then yes, absolutely it must be turned on. And this is for the simple reason that the Megafile 60 pass through connection is actively buffered, it is not passive (as is i.e., on most Atari 8-bit SIO devices). Some signals will simply not reach the second hard disk if the Megafile is turned off.

 

But there is no universal answer to the question as stated at the thread title. It depends on the specific host adapters. Some use a passive pass through connection, some ICD adapters are allegledly "smart" with logic that adapts depending on the other devices.

 

[Calab]

45 minutes ago, ijor said:

In the exact example you describe, the Megafile being first in the chain, then yes, absolutely it must be turned on. And this is for the simple reason that the Megafile 60 pass through connection is actively buffered, it is not passive (as is i.e., on most Atari 8-bit SIO devices). Some signals will simply not reach the second hard disk if the Megafile is turned off.

Thanks for the info folks. Looks like I'll be setting up my drives differently then.  I don't want to run the MegaFile very often. I was just hoping to avoid having to unplug/replug cables on the odd occasion that I did want to use it.

Does anyone know if a "Y" type cable would work? Middle of the Y plugged into the ST, one arm plugged to the MegaFile and the other to the UltraSatan?