This item is from the Yet Another Enhanced IDE/Fast-ATA/ATA-2 FAQ, by John Wehman and Peter den Haan with numerous contributions by others. (v1.92).
Do not confuse this with Smartdrive (or whatever) lazy writes: what is meant here is altering the drive's buffer cache management algorithm. This is possible using newer versions of Drive Rocket, with hdparm under Linux, and probably other utilities too. Provided, of course, the drive supports this feature. Sometimes it can also be done using jumpers on the drive.
There seem to be problems with this, if a program will issue a soft- reset (which on Intel Pentium Motherboards also issues a hardware- reset) as soon as it sees the last IRQ, which overall ends up corrupting data. Use with care, and backup.