[sebhc] HDOS sysgen questions (and problems)

Glenn Roberts gfroberts at adelphia.net
Wed Oct 18 20:47:39 CDT 2006

yep it's normal.  if you enjoy reading source code check out


the ABR routine (Auto Baud Rate Selection, line 1938) cycles the UART 
through various BAUD rates and waits for a reading that doesn't cause an 
error, then sets that as the default BAUD rate. 25  years ago I could 
have pointed you to the code that writes this back to the boot track (so 
that on subsequent boots you don't have to hit space) but now I'll have 
to leave that as an exercise to the reader! (it's in there somewhere).

If you were fortunate enough to have an H8 you probably avoided this 
trap ... the code spells out "SPACE" on the LEDs as a hint to hit the 
space bar!

The manuals are also in the SEBHC archive. the Bootstrap procedure is 
described at:


starting at page 1-13.

- Glenn

Bob Shannon wrote:
> Doh!
> So it was working all along!?
> Clearly I have a lot of reading to do.
> So it appears that once its figured out the baud rate, the O/S
> patches itself, and does not auto-baud when you re-boot the disk?
> After pressing the space bar twice, I got the BOOT text and
> HDOS sign on messages.  When I rebooted that same floppy
> later on (without powering off) it simply booted up automatically.
> No need to press the space bar. 
> Is this normal?
> ----- Original Message ----- From: "Mark Garlanger" <garlanger at gmail.com>
> To: <sebhc at sebhc.org>
> Sent: Tuesday, October 17, 2006 5:08 PM
> Subject: Re: [sebhc] HDOS sysgen questions (and problems)
>> On 10/17/06, Bob Shannon <bshannon at tiac.net> wrote:
>>> Ok, I'm stumped here!
>>> How do I make a bootable system disk under HDOS?
>>> I'm able to init and pass media check on a 'blank' floppy.
>>> But when I SYSGEN/M, and attempt to boot the resulting
>>> diskette, nothing happens.
>> At this point try pressing the space bar 3-4 times, it's to determine
>> baud rate, there is set commands to not require it, I'm not sure if
>> SYSGEN/M is some how reseting that option, but it's worth a try. I had
>> seen this with some of the disks I had (HDOS distribution disks). I
>> thought the disks had gone bad - I then attempted to mount them, and
>> they worked fine... then I remember about the space bar and that fixed
>> the problem.
>> Mark
>>> Specifically, I reset, press B for 'boot', the drive light goes on
>>> then off again, then nothing happens.  No additional text is
>>> displayed, no drive access sounds, nothing.
>>> When I try SYSGEN *.* I get a read error on the source
>>> disk and end up back at the HDOS prompt.  The resulting
>>> disk does not boot, it acts exactly like the SYSGEN/M
>>> attempt.
>>> When I simply try SYSGEN, I end up with an error where
>>> the system is looking for ONBECOPY.ABS, which does
>>> not appear to be on my one and only bootable diskette.
>>> Would someone here please tell me exactly how I'm supposed
>>> to make a backup boot disk?
>>> -- 
>>> Delivered by the SEBHC Mailing List
>> -- 
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