Yousuf Khan wrote:

On 4/25/2020 6:15 PM, Martin Leese wrote:
Hi,

I am transferring an old hard disk (20 Gbyte
Maxtor D740X) from an old PC to a newer one
(Dell Dimension 3000).* On the old machine
the disk was the boot drive, and so was
configured as the Master device. On the newer
machine it will be a Slave device.

I have the "Jumper, CHS, and Install Guide"
for the drive, but there are two Slave
jumper settings.* These are called "Slave"
and "Slave with AC", but nowhere does the
document explain was "AC" actually is.
(There is also "Master with AC" and "Cable
Select with AC".)* What is "AC"?

I can't Google at the moment because my old
PC does not have the required encryption
protocols.* This is why I am trying to
upgrade.

I guess so far there's been no explanation of what the "AC" means yet.
My guess is that it probably stands for "Address Control" or something,
which might be a way of getting an older BIOS to understand a newer
drive. I think around this time most drives used the older CHS
(Cylinder, Head, Sector) formatting system, and to get bigger the new
generation had to switch to the newer LBA (Logical Block Address)
system. Address Control might indicate to the BIOS whether to use the
CHS system or the LBA system. Later generation BIOSes could figure this
stuff out on their own.

Even for BIOSes that supported LBA, they were and still are limited to
the number of addressing bits. At one time, 22 bits was thought
sufficient for IDE/ATA drives. Then 28 bits. Now it's up to 48 bits.
If that isn't enough for the partition size, up the entity size
(sectors). Hard disks have implemented LBA (Int13 extensions) since
1996 rather than rely on a CHS translation scheme in the BIOS.

https://en.wikipedia.org/wiki/Logica...dressing#LBA48
"The current 48-bit LBA scheme was introduced in 2003 with the ATA-6
standard,[4] raising the addressing limit to 248 × 512 bytes, which is
exactly 128 PiB or approximately 144.1PB."

One day, partitions will get bigger than that, and we'll need more or
different specs to address those super-sized drives. Or come up with an
entirely different addressing scheme.

The Maxtor D470X was introduced back around 1996 as part of their
redesigned DiamondMax family line using TI DSP-based architecture. That
was well back in the era when there were BIOSes with and without LBA, so
lots of drives had to cover old and new PCs at that time to maintain
their revenue. The OP wants to put that old Maxtor HDD into a Dell
Dimension 3000 the latter of which was introduced in 2004 (we don't know
what box that drive was in before). That PC will have LBA support. The
AC (aka CLJ) jumper is not needed on that old drive, because it isn't
going into a pre-millenial PC. The jumper wasn't needed in his old PC.
It won't be needed in his new[er] PC.