[Coco] CocoSDC booting OS9

[Brett Gordon]

Gene: excellent! .. I see where the superblock only has a 2 byte value
for the size in *bytes* of the allocation map... my mind translated
that to a 16 bit number of *sectors*  Whoops!   Then your calculation
was correct.  This also mean that having a boot-track could NOT
conflict with the allocation bitmap.  ME a Dummy!

This means that Bob's original concern over the boot track getting in
the way of RBF sector allocation is unfounded?

On Tue, Nov 18, 2014 at 10:02 AM, Gene Heskett <gheskett at wdtv.com> wrote:
> On Tuesday 18 November 2014 07:43:20 Brett Gordon did opine
> And Gene did reply:
>> As of now, HDBDOS only support the standard FDC emulation of SDC.  The
>> LBA mode of SDC isn't support by HDBDOS, until someone writes a driver
>> for it. I might take up that project of the toolshed people see fit,
>> as it will benefit the community plus help my cocoboot project (which
>> borrows the HDBDOS drivers for its harddrive/DW)
>>
>> Usually, I think most user partition there HD's with OS9 at the
>> beginning, and HDBDOS *after* it.  With Boisey's Super Driver for OS9
>> you can partition the drive the other way around with HDBDOS drives
>> taking the lower partition and OS9 the higher. If you format your HD
>> this way, then you have the ability to create a bootdisk that is
>> readable from HDBDOS (and the DOS command) solve the Bob's proposed
>> dillema.
>>
>> To answer Bob's original question:
>>
>> At clusters of 1 sector (the defacto standard?), a Combined OS9 RBF
>> with a boottrack can be:
>>
>> 630 sectors - 18 boottrack - 1 superblock = 611 sector for allocation
>> bitmap X 256 bytes per sector = 156,416  bytes for allocation bitmap
>> X 8 bits per byte = 1,251,328 bits in allocation bitmap
>> X 256 bytes per sector = 320 Megs
>>
>> -Brett
>
> Sorry Brett, but the allocation map is hard limited to 65536 bytes. We
> expand for up to 4.2Gb by making one bit in the map correspond to more
> than one sector on the media.  The 4.2Gb limit is reach when we are out of
> LBA addresses with only 24 bit sector addressing.
>
> So above, the one sector per cluster bit maximum is just a hair over 131
> megabytes.
>
>> On Nov 17, 2014 10:20 PM, "Robert Gault" <robert.gault at att.net> wrote:
>> > 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.
>> >
>> > I don't have the SDC and don't know how it is supposed to work. If it
>> > supports HDBDOS and can accept a .vhd such as is used by a real Coco,
>> > the JCV, MESS, and VCC emulators, then it is trivial to place a
>> > 35-track single sided "disk" in the Disk Basic portion of the .vhd.
>> > That is your OS-9 boot disk and there is no need to worry that OS-9
>> > and Basic use different directory structures.
>> >
>> > You can also set up the boot disk for automatic booting at turn on,
>> > if you only use OS-9.
>> >
>> > Robert
>> >
>> >
>> >
>> > --
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>> > Coco at maltedmedia.com
>> > https://pairlist5.pair.net/mailman/listinfo/coco
>
>
> Cheers, Gene Heskett
> --
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-- 
Brett M. Gordon,
beretta42 at gmail.com