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Re: "Universal Boot Initializer" ?


Steve,
I am not totally sure what you're after, but if I got your questions right: 


On Sat, 14 Jan 2012, Steve Nickolas wrote:


Weeeeeeeeell...

Of the first 3 tracks, here's usage for a DOS 3.3 48K slave:

 0123456789ABCDEF
0##### ##########
1################
2#####


Is T0/S5 missing for a reason?


Would it be possible to change usage to something more like this?

 0123456789ABCDEF
0#####
1################
2##### ##########
Moving part of T0 to T2 is just a matter of loader for booting purposes. "INIT" would have to be rewritten, but it's screwed anyway since track #0 has to be written with non-standard format. 

As we already agreed to, "INIT" is prime sacrifice. ;-)
and then stuff two versions of the first 5 sectors onto the same track 0? (i.e., a 16-sector version and a 13-sector version).
Ok, I guess you want to keep T1..T22 in 16-sector format, only T0 is funny. 

Here's something even more easier to do and maintain:
Put one 16-sector and one 13-sector S0 on T0. Fill the rest of the track with "macro" sectors encoded in 18-sector format, just as we discussed recently. The beauty of this approach is that the code in both S0 will be exactly the same for 13 and 16-sector cases - it will contain loader for the "macro" sectors from T0. In case 256 bytes aren't enough for such a loader (and you can't rely on the bootstrap ROM), revert to some simple scheme, even 4&4. But the layout of 18-sector "macro" sector is very easy and straightforward. 

Again, you write T0 in single pass.
Now, the only problem with this scheme is that you want to have 16-sector format with 13-sector P5/P6 PROMs on the disk controller. Not reliable and you can't expect (I think) that users will have lucky combination of 16-sector sequencer PROM and 13-sector bootstrap PROM. (Consult Sather's "Understanding the Apple II" for details)
So, to be on the safe side, you have to keep the whole disk in 13-sector format, and the "macro" portion of T0 to be in either something analogous to 18-sector format but with 5&1 encoding, or plain 4&4 for simplicity.