Thats what I was looking for, a litmus test! So what that means is the original HD20 startup disk will not work with older systems. I'll bet System 3.0 & Finder 5.1 (or maybe even 5.0) will work just fine with a newer system. I read an interesting article in MacTech that detailed the changes thoroughly and SYstem 3.0 and up really changed the System resources considerably.
Otherwise, I think we are starting to repeat ourselves! LOL At this point I am interested in the pure mechanics of how the HD20 INIT works and not so much the practicality of it. I think we have the MFS formatting dilemma behind us.
As for MFS partitioning, of course it works. I have an application called MacServe which was the original AppleTalk disk serving and network printer software dating back to the Lisa. Essentially that allowed you to partition an HD 20 with HFS & MFS volumes. And originally they were MFS only. I saw it explained somewhere that HFS folders are basically just disk partitions. Since my HD20 is currently not working, I have set this up on a ZIP 100 drive running System 3.2/F5.3 that boots the Mac. The key is, the drive must be formatted according to the manufacturer instructions. So the HD20 (like the ZIP) must be initialized HFS, then MacServe partitions the drive however you want.
I'm basically curious if the HD20 could be initialized completely MFS and therefore used with an MFS only system. I agree partitioning it would be the only practical way to use it.
I would certainly be interested in the results. And if using my ZIP 100 drive is any indication, entirely possible. As long as the Mac can see and understand the drive and there is a system on the drive that the Mac understands, then it shouldn't matter what version it is. However, as you pointed out Finder 4.1 is NOT HFS aware. I believe that the normal version of the HD20 INIT makes System 2.1 HFS aware, but does nothing for the Finder which is why the System can see HFS formatted disks, but cant write to them, or discern their contents & folders. That seems to be the Finder's job, to find the folder "partitions" or file structures. However, you wouldn't want to use such a system if it did work since you would royally screw up your data by writing files MFS onto an HFS formated disk. The only variable is whether something in the "hand-off" would prevent it from loading.
There is a lot of info on these pages of invaluable nature for working with and further investigating an 800K drive, HD20 and MFS/HFS Systems. However, the main goal of working with 800K MFS disks has been achieved by not one, but two and conceivably other methods. Clearly the HD20 is best formatted for practical use as an HFS drive and partitioned accordingly using existing software and other solutions. I will keep working on the MFS issue for the large volume access on a 128K as that is where my goal lies and report back, but until someone is ready to initialize an HD20 most of it will be theoretical.