johnklos
Well-known member
A few people have asked how I make use of modern SCA SCSI disks with older machines.
Since high end 10000 or 15000 RPM 3.5" drives are overkill speedwise, and since most of us don't really need 300 gigs on our older machines, I've settled on 70 gig 2.5" disks such as the IBM 90P1316, the IBM 90P1313 and the IBM 26K5158. They're 10000 RPM drives which can communicate at Ultra-320 speeds ,so they're still much more than we generally need, but they're comparatively new, require less power than a 3.5" disk (although they still do require 12 volts) and they're cheap at around $15 USD each.
Next, we have to reliably connect them to our computers. There are common SCA to 50 and 68 pin adapters which look like this:
With this particular type, even though we see terminators, they don't seem to terminate the bus properly. What works consistently and reliably with this kind of adapter is a 68 pin terminator, a 68 pin cable, and a 68 to 50 pin adapter. This has the advantage of letting you use a physically narrower cable which may be easier to route.
Some people don't like using 68 pin cables and adapters, but a common issue is that if the upper bits on a wide SCSI bus aren't properly terminated, drives sometimes won't negotiate down to an 8 bit bus, which means the drives won't show up on your older machine. As I said, with a 68 pin terminator and cable, this will work reliably.
Here's the 68 to 50 pin adapter, which gets installed in the 50 pin SCSI header of your computer:
What this looks like when you're done can be like this, which you can see isn't bad considering the amount of space available:
or like this, which is quite tidy and actually is more out of the way than the usual 50 pin cable:
There are other SCA adapters with proper termination built-in, which I'll cover soon. I hope this helps
Since high end 10000 or 15000 RPM 3.5" drives are overkill speedwise, and since most of us don't really need 300 gigs on our older machines, I've settled on 70 gig 2.5" disks such as the IBM 90P1316, the IBM 90P1313 and the IBM 26K5158. They're 10000 RPM drives which can communicate at Ultra-320 speeds ,so they're still much more than we generally need, but they're comparatively new, require less power than a 3.5" disk (although they still do require 12 volts) and they're cheap at around $15 USD each.
Next, we have to reliably connect them to our computers. There are common SCA to 50 and 68 pin adapters which look like this:
With this particular type, even though we see terminators, they don't seem to terminate the bus properly. What works consistently and reliably with this kind of adapter is a 68 pin terminator, a 68 pin cable, and a 68 to 50 pin adapter. This has the advantage of letting you use a physically narrower cable which may be easier to route.
Some people don't like using 68 pin cables and adapters, but a common issue is that if the upper bits on a wide SCSI bus aren't properly terminated, drives sometimes won't negotiate down to an 8 bit bus, which means the drives won't show up on your older machine. As I said, with a 68 pin terminator and cable, this will work reliably.
Here's the 68 to 50 pin adapter, which gets installed in the 50 pin SCSI header of your computer:
What this looks like when you're done can be like this, which you can see isn't bad considering the amount of space available:
or like this, which is quite tidy and actually is more out of the way than the usual 50 pin cable:
There are other SCA adapters with proper termination built-in, which I'll cover soon. I hope this helps
