It is possible - for ages. Intec wrote the driver that uses built in IDE controllers that are limited to the 128GB (not MB like I wrote in my last posting), and can use them with virtually any size. So you can use about any disk size in IDE Macs with onboard controllers. See here: http://www.speedtools.com/HDInfo.html
After working with Macs and PCs since the inception, to be honest this approach absolutely sucks. I strongly recommend against any "low level" drivers or "dynamic drive overlays" as they used to call them in the PC world. The main issue is that they will, in the end, lead to data loss. if there are any issues, whatsoever, these "low level" overlays will cause major problems if you move the drive to another system for data recovery. Remember, if the overlay does not load, then the drive will appear "foreign" to all over systems it is connected to. I have personally seen, many instances of a client loosing everything. some go to inexperienced PC/Mac repair places that tell them their drive is "empty" or worse yet, format it, since they "assumed" it was empty because they did not realized it had an overlay to see the drive partitions and stuck it in another Mac or PC without booting to it... which is common when you are having a boot problem and you bring your computer in for service.
As a big advocate Hard disk speed tools for many of their tools, I still do NOT recommend using this feature.
Lastly, as a side note, I have also seen some volumes not mountable in macs that do not have HD Speed Tools installed when you add a hard drive as a secondary drive (that had HDTS installed) to a G4, even though the source MDD and destination MDD both supported large IDE drives. The fix is to install HDTS on the boot volume of the destination MDD, and then everything is fine. Remember, HDTS, updates the original Mac OS 9 driver on the hard drive and assumes you will be booting from a volume that has HDTS installed on it. Sometimes it is not an issue moving drives to units without HDTS, and sometimes it is... I personally hate random variables, so I suggest using HDTS for it's other cool features and NOT updating the drivers on your hard drives as this can add an unwanted side effect when you need to recover data... just an opinion... do whatever suites your needs
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