>First, can anyone point the direction of info regarding subject??? Would
>like to read/see the difference of SCSI through the years ~ it might help
>me to better understand the difference between 1, 2, Narrow, Wide, Fast,
>etc.
www.scsifaq.org is a *great* source of info.
It's pretty easy though, here goes:
bit width ---- narrow = 8bit, wide = 16bit
pin # ---- narrow = 50pin, wide = 68pin
so just think that per speed grade wide scsi can transfer twice as much,
because it doubles the bit width. These speed grades are *theoretical*
maximums, also. You won't see these exact speeds. I'm not going to get into
Ultra160 and above, because it's not really relevant to this list and adds a
whole bunch of other confusing factors.
narrow | wide
normal 5MB/s | 10MB/s
fast 10MB/s | 20MB/s
ultra 20MB/s | 40MB/s
ultra2 x | 80MB/s
pretty linear, eh?
Now for connectors. The label "SCSI 1" actually refers to a command set, but
it has been applied to the connectors that were standard at the time.
SCSI 1 --- 50-pin centronics
SCSI 2 --- high-density 50-pin DB
SCSI 3 --- high-density 68-pin DB
The 25 pin DB connectors that Apple used for external scsi is a
bastardization of the SCSI 1,2 50-pin connector. Each data line is supposed
to have it's own independent ground, but they tied them all together to save
space. That means you will get noise on the lines (==corrupt data) if you go
over 5MB/s. But it's a moot point because Apple's external SCSI never went
faster than that.
>Second, have purchased 3 different external HDD cases, all different (noted
>below) ~ is there a general rule that determines which port is 'in' and
>which is 'out' when considering chaining (does it matter)?
(snip)
What you have is three SCSI 1 external cases. It doesn't matter which one
you plug in/out cables into. Just make sure no jacks are "open". Each 50-pin
jack should either have a cable running to the computer or another scsi
device, or be terminated with an external terminator.
>Third, will 800K floppies play nicely in a 1.44Mb drive??? Still confused
>after reading the FAQ, LEM and others :(
Yes. Superdrives are backwards compatible with 800k "lacklusterdrives".
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