[Coco] CocoSDC booting OS9

[Bob Devries]

I understood from the documents, that the CocoSDC has an LBA mode. I'm 
assuming that this can be used with large disk images?

I know no more about it other than the one reference in the PDF file.

Regards, Bob Devries
Dalby, QLD, Australia


On 18/11/2014 12:03 PM, Brett Gordon wrote:
> That sounds like a fine idea!  It's just a matter of changing OS9 and
> BASIC to agree to do something different.
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> On Mon, Nov 17, 2014 at 6:37 PM, Bob Devries <devries.bob at gmail.com> wrote:
>> Unlike Nick, I don't dabble in BASIC. I'm exclusively an OS9 user.
>>
>> Tricking the DOS command into thinking that the disk is a *standard* disk
>> limits the size that the disk can be, because the sector allocation table
>> starts at sector 1 and continues for 1 byte for every 8 sectors until all
>> the disk is accounted for. This means that the disk's size *must* have a
>> sector allocation table of less than 612 bytes. This means that I would have
>> a relatively small boot disk, which to my mind is a waste.
>>
>> Regards, Bob Devries
>> Dalby, QLD, Australia
>>
>>
>> On 18/11/2014 8:34 AM, Brett Gordon wrote:
>>>
>>> Bob:
>>>
>>> BASIC can only access so much drive (much less than OS9).  I think the
>>> SDC docs explain some of the assumptions SDC DOS makes about Large
>>> Disks.  The DOS command ALWAYS loads the Boottrack from logical Drive
>>> 0, Track 34, sectors 1-19.  Once the second stage is loaded (BOOT and
>>> REL, and those fellows)  the entire disk is available.   Its a minor
>>> problem very similar to Linux's LILO Bootloader had: BIOS limited the
>>> kernel file to the first 1024 Cylinders.  But after the kernel was
>>> loaded really big disks where accessible.   I'm assuming the OS9GEN or
>>> COBBLER take care of making sure the boottrack is where its supposed
>>> to be at (and marks those sectors as used in OS9 )
>>>
>>> Shameless plug:
>>> Try my boot-trackless booting:
>>> http://sites.google.com/site/cocoboot2.  Any Nitros9 compiled from
>>> source in the last couple weeks supports it.
>>>
>>> On Mon, Nov 17, 2014 at 4:53 PM, Bill Pierce via Coco
>>> <coco at maltedmedia.com> wrote:
>>>>
>>>>
>>>> Bob, I think (but not sure), the whole basis of these "big disks" with
>>>> custom NOS9 boots is that if you're booting from HDBDOS and/or DW4 (how else
>>>> would you use them?), DW4 doesn't know about disk size (and doesn't care),
>>>> and as long as the kernel is on track 34 when you type DOS, HDBDOS will load
>>>> it. For that matter, with a little modding, the kernel can be on disk 255 of
>>>> an RSDOS/OS9 partitioned drive and still boot :-) After that, RSDOS/HDBDOS
>>>> is no longer in control and the whole process is determined by the "boot"
>>>> file in the kernel... be it dw4, becker, cocosdc, superide... whatever. The
>>>> "boot" for that kernel is setup for that bootfile and it "Just Works"(tm)
>>>> Ingenious I tell ya... FREAKIN INGENIOUS!
>>>>
>>>> BTW... I was told not to worry about stuff like that... that it was just
>>>> Majic and not to question it or it would go "poof!".
>>>>
>>>>
>>>> Bill Pierce
>>>> "Today is a good day... I woke up" - Ritchie Havens
>>>>
>>>>
>>>> My Music from the Tandy/Radio Shack Color Computer 2 & 3
>>>> https://sites.google.com/site/dabarnstudio/
>>>> Co-Webmaster of The TRS-80 Color Computer Archive
>>>> http://www.colorcomputerarchive.com/
>>>> Co-Contributor, Co-Editor for CocoPedia
>>>> http://www.cocopedia.com/wiki/index.php/Main_Page
>>>> E-Mail: ooogalapasooo at aol.com
>>>>
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: Bob Devries <devries.bob at gmail.com>
>>>> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
>>>> Sent: Mon, Nov 17, 2014 4:02 pm
>>>> Subject: [Coco] CocoSDC booting OS9
>>>>
>>>>
>>>> Hi all,
>>>>
>>>> I don't have my CocoSDC yet.... (soon!)
>>>>
>>>> I was looking through the NitrOS9 repo and found a disk image which can
>>>> be used with it. I was surprised to see that even though it's a ~4.5MB
>>>> disk, it can still boot OS9 without any extra disks.
>>>>
>>>> Now that makes me wonder what the largest size a disk can be and still
>>>> be bootable under the current boot method. The limitation would seem to
>>>> be $0264 sectors for the sector allocation table, since the DOS command
>>>> gets the kernel track from there (34 tracks * 18 sectors = 612 ($0264)).
>>>>
>>>> Perhaps the "DOS" command could be made more intelligent by having it
>>>> check the size of the disk by grabbing the first three bytes from LSN0,
>>>> and then subtracting 18 sectors, and load the kernel track from there,
>>>> thus putting the kernel out of the way of the sector allocation table,
>>>> and thereby allowing for almost any size (hard) disk.
>>>>
>>>> One gotcha would be if the file system used a cluster size of more than
>>>> 1, which would make the allocation of the kernel's sectors in the sector
>>>> allocation table a bit more curly.
>>>>
>>>> Chris Burke used a method by which track 128 of the drive was used as
>>>> the kernel track, but IIRC it could be changed. He also had utilities to
>>>> allocate the sectors in the sector allocation table.
>>>>
>>>> My $0.02
>>>>
>>>> Regards, Bob Devries
>>>> Dalby, QLD, Australia
>>>>
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>>>
>>>
>>>
>>
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