[sebhc] H-8-IDE board

West, Ronald S. RONALD.S.WEST at saic.com
Thu Jul 22 13:59:48 CDT 2004

Thanks for all the good advice folks. If the group table is using bytes for
group numbers then sounds like the limit will be the 250 value mentioned.
Will see when I get into the device driver writing. Hmmm.... May have to
take Walt up on his offer <hehe>. 

Making it look like an H67 might be a good idea also. Don't know much about
the 67, will have to look at the manual and device drivers.

Btw - I have a set of hard sector floppies purported to contain most of the
source code for HDOS 2.0. I forget who gave them to me... It was a long time
ago. If I can get them to read will post them to the web site.

Wonder if some of these issues were taken up in 3.0? Does anyone know if
they addressed the affinity for 256 bytes and the fact that HDOS uses a 16
bit word to address sectors, which is where I got the 65535 limit. Walt (I
think) said something about not using all 512 bytes in a sector. That might
be a good idea too. All depends on what I find when I start issuing commands
to this thing.

Even with all the above limitations we should have a machine that really

Being a system administrator type I don't get to use my training in hardware
design I spent so much time learning. Scary, but this is a lot of fun!

Keep the good suggestions coming.


> -----Original Message-----
> From: sebhc at sebhc.org [mailto:sebhc at sebhc.org] On Behalf Of 
> Steven Parker
> Sent: Thursday, July 22, 2004 1:26 PM
> To: sebhc at sebhc.org
> Subject: Re: [sebhc] H-8-IDE board
> >>Due to the way HDOS 2.0 (don't know if
> >>3.0 is different) allocates files it will only store 400 files per 
> >>disk (including system and directory files).
> >
> >Are you certain about the 400 files?  I haven't given the 
> source code a
> >good look in a long time, but I thought that the limit was 
> about 250 files.
> You can't have more files than allocation groups, and the 
> group table index 
> for a floppy is one byte.  H-17 floppies had 200 allocation 
> groups, but I've 
> made fantasy floppies for the simulator with 250.  The total 
> capacity has to 
> be a common multiple of both the allocation size and the 
> number of sectors 
> per track.
> I don't recall the H-67 layout though, perhaps it got around that 
> limitation.  You'd probably want to set up your driver to 
> make your IDE 
> drive look like an H-67 to the system rather than a bunch of floppies 
> anyway.
> Cheers,
> - Steven
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