There is a maximum number of FIDs that the empeg can handle at one time, about 21000. Each playlist and each track take up one FID. If you try to play a playlist that contains too many FIDs, it won't be able to store them properly, and it will forget what it's been playing when you reboot.

The maximum number of FIDs is determined by the size of a part of your hard drive. This part was allocated at the factory, or the last time you ran the "drive builder" image, if you ever did. The thing is, when it was allocated, it requested 16MB (that might not be the right size, but it's irrelevant). But the way hard drives work, they have to allocate space in chunks of particular sizes. If your particular hard drive allocates in 16MB chunks, then it allocated exactly 16MB. If it allocates in 8MB chunks, you got exactly 16MB. But if it allocates in 32MB chunks, then you got 32MB. Or if it allocates in 10MB chunks, you got 20MB. The problem is that the software thinks that you have 16MB, regardless of how much space is actually there. The maxfid patch checks to see how much space is actually available, and modifies the software so that it will use all of it.

So, if you ever have problems where you play a large playlist and the empeg forgets about it when it restarts, then you have a problem that might be fixed by the maxfid patch. If you don't have that problem, then it's not going to do anything for you. But it shouldn't hurt anything either.