Write Precompensation Cylinder (WPC)
Applicability: Hard disk drives that use the ST-506/ST-412 interface (commonly referred to as MFM).
WPC is the cylinder of the hard drive at which write precompensation starts.
If the WPC of a drive is shown as zero, that means that precompensation is required to ALL cylinders.
If the WPC is shown as "none" or "N/A" or "-1" or "65535", that means that no precompensation is required.
Using the wrong WPC will not stop the hard drive from booting/operating.
WPC was important back in the days when personal computers were used to store important business information.
These days, in a hobby environment, it is not important.
Detailed information on write precompensation follows.