[sebhc] H-8-IDE board - HDOS 3.0

[Bill malcolm]

Sounds GREAT.

RE: CP/M  device parms can be set to NOT check the disk -- called I think, 
directory check, this is normaly used for hard disks &  ram disks.
bill.



>From: Jack Rubin <jack.rubin at ameritech.net>
>Reply-To: sebhc at sebhc.org
>To: sebhc at sebhc.org
>Subject: Re: [sebhc] H-8-IDE board - HDOS 3.0
>Date: Thu, 22 Jul 2004 09:16:59 -0700 (PDT)
>
>Don't forget that we have full HDOS 2.0 and 3.0 source
>available. 3.0 is in the archives and I'll be glad to
>scan and post any part of 2.0 on an as-needed basis
>since the full listing is a foot-high printout. I also
>have HDOS 3.0.x on disk and hope to have images
>available shortly (??). In the meantime, I could
>provide copies on disk for development purposes.
>
>Walt - I just got a couple H47 and H67 subsystems;
>hopefully I'll have something running in the near
>future. At least the units power up without smoking
>and there isn't too much rodent residue involved. But,
>man, those things are heavy!
>
>Jack
>
>--- Walter Moore <waltm22 at comcast.net> wrote:
> >
> > >Soon as I get it built will write a small program
> > to write test data to the
> > >drive. After verifying the board works (reliably),
> > will write a device
> > >driver for it. If all goes well the drive should be
> > able to store 65535 x
> > >512 = 33,553,920 or 33.5 mega-bytes. 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). The neat
> > thing is we may be able to
> > >create SY0 through SY9 (10) disks on one hard
> > drive. That will make up for
> > >the limited number of files. The device driver will
> > do the mapping between
> > >drives. Due to memory restrictions I think HDOS
> > only allows 3 or 4 drives to
> > >be mounted at any one time so some creative drive
> > management may be in
> > >order.
> >
> > 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.  I seem to recall that the allocation tables
> > were all 8-bit, and
> > 0xFF and 0xFE were taken.
> >
> > You might only get 16M of file space.  The H-47
> > driver had to do some work
> > to make 128 bytes sectors work under HDOS - HDOS
> > really wanted 256 byte
> > sectors.  The file system tracked group (8-bit
> > number) and sector within
> > group  (8-bit).  Everything was assumed to be 256
> > bytes.  (Remember that
> > Reagan was just starting his first term when I
> > really last looked at this!)
> >
> > With the size of current drives and slowness of the
> > H8 and small memory, I
> > would consider throwing away half of every sector so
> > that I didn't get into
> > read/modify/write for short sectors and having to
> > allocate extra memory for
> > the RMW.  This is just a thought.  The performance
> > trade-off might not be
> > worth it.  (Can you low-level format an IDE drive
> > for 256 byte sectors?)
> >
> > I also believe that 8 units is the max (bit flags in
> > a byte are used).  I
> > don't recall any restriction on number of mounted
> > drives.  The buffers and
> > allocation tables were dynamically allocated, but
> > then I never had a chance
> > to use a device with 8 units so maybe there is a
> > limit I missed.
> >
> > I wanted to write a driver where you could change
> > the number of units, but
> > ended up deciding that this could not be easily
> > done.  The number of units
> > and capabilities mask were part of the device driver
> > preamble which was not
> > written back out to disk.  Darn.  I guess this is
> > why they never fully
> > implemented it for the H-47 driver.  A good idea
> > might be to use the set
> > command to map unit number to "partition" and have a
> > couple of the unit
> > numbers be set for read-only.
> > This mapping might only apply on boot, I don't know
> > if they can be
> > dynamically changed for a directory device.
> >
> > I had a friend who added a Corvus 10M hard drive to
> > his H8 back around
> > '82.  It screamed.  I believe he made each unit 2M.
> > It was a lot faster
> > under HDOS than CP/M because CP/M always wanted to
> > check to see if the disk
> > had been swapped while HDOS relied on the "Mount"
> > command (he wasn't a CP/M
> > expert and my have missed something that would have
> > allowed it to be faster).
> >
> > Anyway, if I can get back up and running sometime
> > soon, I'd be willing to
> > help out with the device driver.
> >
> > ..walt
> >
> >
> > --
> > Delivered by the SEBHC Mailing List
> > sebhc-request at sebhc.org.
> >
>
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