3 Sep
2006
3 Sep
'06
1:14 p.m.
Don wrote:
Hi,
I want to move my scanners over to one of these Macs
(probably the 840AV since I can also exploit the video
capabilities thereof).
But, it's got those wacky DB25 SCSI connectors. :-/
I have DB25-Centronics cables. And, DB25-HD50 adapters.
The scanners have a hodge-podge of *different* connectors
(sheesh! talk about "standards"... :< ).
I assume a good goal is to minimize *connections* wherever
possible. So, instead of DB25-HD50 adapter to HD50 cable,
use DB25-HD50 cable, if possible.
But, I'm nervous about the DB25's and their roles in all this.
Is this just a regular SCSI (narrow, SE) bus with a few less
returns? Or, are there other consequences of this connector
choice?
E.g., how much grief can I expect going *through* the slide
scanner with DB25 coming in and Centronics going out? Is
this just effectively a "DB25-Centronics" adapter with a
device tap in the middle?
Thanks!
--don
The main thing to worry about when the DB25 is involved
is that the cable that is used is scsi certified. The round cable
that is usually used between the two connectors if it is there
has a special way of positioning the req and ack signals
in the bundle of wires. Other than that, the standard specified
the connector, so that should be no worry.
I know early on, some cables were made and just used that
may not have been SCSI certified, and in early "vintage" systems
you may run across such, and have noise or performance
problems with the devices, if the REQ / ACK / Select signals
get messed up.
Only when you go from 50 -> 68 pin should you beware of
termination on the upper 8 bits added by the extra lines and
what you have for an initiator and targets.
There is not much science in a wide initiator selecting narrow
devices on a chain, but there is when you have wide targets and
a narrow initiator.
but you don't have that from what I read, so it is just a matter
of haveing a bit of everything in the chain connetorwise, but
the SCSI bus should all be the same.