[Coco] CocoSDC booting OS9

[Gene Heskett]

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
> > 
> > 
> > 
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > https://pairlist5.pair.net/mailman/listinfo/coco


Cheers, Gene Heskett
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