Steve Nickolas

On Sun, 15 Jan 2012, Vladimir Ivanov wrote:

>
> 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. ;-)

So it has to be done with a separate program. The tool wouldn't fit in
INIT space anyway.

>> 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.

I dunno if it'd work that way. Might have to be a 4-track 13-sector DOS.

> 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)

Which is why these disks usually run some form of DOS 3.2 (Bob
Sander-Cederlof's assembler documentation for an early version actually
mentioned using a 16/13 DOS 3.2.1), and one I've seen runs a form of 3.1.

>
> 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.
>

Yeah.

-uso.

Steve Nickolas

Replying to myself.

The best I can see the usage of DOS 3.2 with a 16-sector bootstrap would
be to use 3.5 tracks, rather than 3, thus:

Track usage as seen from DOS 3.3 on the left, 3.2.1 on the right.
# - native sector. % - non-native "sector", shown stretched or squashed by
410/342. (this may be inaccurate)

0123456789ABCDEF 0123456789ABC
0##### %%%%%% ##### %%%%
1%%%%%%%%%%%%%%%% #############
2%%%%%%%%%%%%%%%% #############
3%%%%%%% ######

Basically, a few "common" sectors written on track 0 both in DOS 3.2 style
and in DOS 3.3 style, then 2.5 tracks containing the rest of the DOS
image, probably 3.2.1, reordered and with a different loader. It may even
be possible to have track 0 reread AFTER the base rwts is loaded, and load
up to 4 additional sectors there. Maybe others could be freed up and it
would actually fit in 3 tracks, allowing for no loss of capacity.

Formatting would of course require a separate tool... there's no way in
hell to ram all that code into DOS 3.2.1 space.

-uso.

Linards Ticmanis

On 01/15/2012 03:17 AM, Steve Nickolas wrote:

> Basically, a few "common" sectors written on track 0 both in DOS 3.2 style
> and in DOS 3.3 style, then 2.5 tracks containing the rest of the DOS
> image, probably 3.2.1, reordered and with a different loader.

I think the way it was usually done was to have everything in 13-sector
format, except for one single boot sector that can be read by the
16-sector controller card. That sector then just contains an equivalent
of the 13-sector boot ROM and the first thing it does is to simply load
the 13-sector boot sector and jump to it. From there, everything is
almost the same for the two code paths; the 13-sector boot sector is
modified only insofar as it detects whether it has been read in directly
by a 13-sector controller card or by the 16-sector boot sector and
adjusts accordingly (boot sectors generally re-use some part of the
controller ROM routines since they're too small to do anything useful
without that trick).

At least that seems to be what the original release of "Ultima" (later
known as "Ultima I") does, the only universal booter I have looked at in
some detail.

--
Linards Ticmanis

Steve Nickolas

On Tue, 24 Jan 2012, Linards Ticmanis wrote:

> On 01/15/2012 03:17 AM, Steve Nickolas wrote:
>
>> Basically, a few "common" sectors written on track 0 both in DOS 3.2 style
>> and in DOS 3.3 style, then 2.5 tracks containing the rest of the DOS
>> image, probably 3.2.1, reordered and with a different loader.
>
> I think the way it was usually done was to have everything in 13-sector
> format, except for one single boot sector that can be read by the
> 16-sector controller card. That sector then just contains an equivalent
> of the 13-sector boot ROM and the first thing it does is to simply load
> the 13-sector boot sector and jump to it. From there, everything is
> almost the same for the two code paths; the 13-sector boot sector is
> modified only insofar as it detects whether it has been read in directly
> by a 13-sector controller card or by the 16-sector boot sector and
> adjusts accordingly (boot sectors generally re-use some part of the
> controller ROM routines since they're too small to do anything useful
> without that trick).
>
> At least that seems to be what the original release of "Ultima" (later
> known as "Ultima I") does, the only universal booter I have looked at in
> some detail.
>
>

Castle Wolfenstein and Alien Addition are universal booters. The NIBs
have this feature intact.

-uso.

Antoine Vignau

Another one is Softporn adventure by On-line systems,
av