[Coco] error 249

Sat Mar 18 12:49:18 EDT 2017

On Saturday 18 March 2017 11:01:18 Stephen H. Fischer wrote:

> It has been many years since I last used my real CoCo and made the
> mistake of inserting a NitrOS-9 DNS=3 formatted disk into a drive that
> had a descriptor set to DNS=1. Actually VCC and other emulators
> running NitrOS-9 can demonstrate the error.
>
> I think that 249 was the error reported. My OS-9 manuals are currently
> unavailable.
>
> I rarely used DNS=1 as all my descriptors normally had DNS=3 for my
> 5-1/4" 80T2S disks (NitrOS-9 will double step to read a 40T2S disk.)
> All most all of my disks I have archives of online have that format.
>
> I needed to use the correct DNS=3 in my system but the CoCo world
> mainly has DNS=1.

This is one of the changes Robert G. and I did to Nitros9 a couple, maybe 
3 years back. Or possibly an interim change. What I wanted to do was 
make a 40 track disk inserted into an 80 track drive into a read-only 
disk automatically in order to protect the disk from being trashed by 
the write of a much narrower track in the middle of its wider 40 track 
magnetic pattern.

This of course only works IF the disks format truly reflects the disk 
characteristics. That, _everybody_, means ALL your 5.25" 40 track disks 
were formatted with dns=1, and ALL you 5.25" 80 track disks were 
formatted with DNS=3.

Now, to confuse the issue because there is no "high track density" step 
mode to any 3.5" disk drive, they are ALL 135 tpi, the DNS in a 3.5" 80 
track descriptor should always be set for DNS=1 as there is no double 
track density mode in any of the drives.

Robert and I fixed the driver, but its up to you folks to fix your 
descriptors, its one of the things delegated to the makefile IIRC.

AIR, I was able to fix my disks with dEd.  But I forget at this late date 
which byte(s) in lsn0 is changed, sorry. The rbf docs should clarify the 
correct byte(s), its in the DD.TYP, and in PD.OPT section both IIRC.

I also do not know if those descriptor changes made it into the actual 
descriptors made by a current Nitros9 build.  So check and correct them 
with dmode using the "dmode -filename" syntax so they'll be set 
correctly until your next update your Nitros9 install.  Then check it 
again after an update.  The reason I don't know is that descriptors are 
IMNSHO for your hardware, and do not, or should not change when you 
update, So I have a saved dir for them, and a script I run after an 
update that overwrites the distributions descriptors that I use here, 
with my own corrected versions.

So thats my solution to that particular Excedrin headache. You may have 
your own and if it gets the job done, fine. My way "works for me."

> It is hard to understand how the mismatch might happen

No its not at all hard to understand, theres whole books worth of bogus 
info out there about this, but you are reading it from the horses 
fingers here folks. Pay attention please.

> for you but 
> DMODE can be used to quickly check the Descriptor DNS setting and the
> utility "lsn0" or another one will read successfully LSN0 and report
> the disks DNS value (It my have a different name, it has been decades
> since I needed to).
>
> Simply changing the descriptor using "DMODE /D0 DNS=3" after the 249
> error and trying the disk again would eliminate this possibility. Your
> 3.5" disks leave you wide open for this problem should you try to read
> any of my own disks. (Ask if you need the 'lsn0' utility)
>
> SHF
>
> ----- Original Message -----
> From: "Bill" <cwgordon at carolina.rr.com>
> To: "'CoCoList for Color Computer Enthusiasts'" <coco at maltedmedia.com>
> Sent: Saturday, March 18, 2017 6:46 AM
> Subject: Re: [Coco] error 249
>
> > Well, that proves the axiom, "Never assume". I had "assumed" that as
> > many years as I've been privileged to be part of this community,
> > someone would "assume" that I was not as stupid as those who had
> > never had ANY dealings with the Coco, and would be "assumed" that I
> > know enough to NOT put an IBM, Atari, or RSDos disk and try to
> > access it.
> >
> > You want information, I will give as much information as I can
> > provide. Actually, I DO have a clean NitrOS-9 formatted disk loaded
> > in my physical drive. And the nos96809l2v030300coco3_dw.dsk has been
> > booted using HDB-Dos 1.4 DW3 Coco 3 into DriveWire 4.3.30
> > (06/13/2013), by a VIRGIN FD-501 Tandy controller controlling a dual
> > vertical set of 3 1/2" drives, and a TRIAD 512K SRAM Upgraded Coco3
> > with no MPI attached that have shown no signs of errors. The Coco 3,
> > DriveWire 4, and the drives have NOT been showing any OTHER SIGNS of
> > errors. The DMODE settings of the /dn drives running with the
> > nos96809l2v030300coco3_dw.dsk had been modified (DMODE /d0 typ=21
> > cyl=50) and re-cobbled.
> >
> > The aforementioned 'problem' floppy  disk had been previously
> > formatted using a disk-based version of nos96809l2v030300coco3_dw
> > with no problems. I had copied Bill Pierce's utilities on it, and
> > was trying to access the disk while the Coco was running DriveWire
> > 4.
> >
> > Any more information will be provided upon request.
> >
> > -----Original Message-----
> > From: Coco [mailto:coco-bounces at maltedmedia.com] On Behalf Of Robert
> > Gault Sent: Friday, March 17, 2017 2:39 PM
> > To: CoCoList for Color Computer Enthusiasts
> > Subject: Re: [Coco] error 249
> >
> >>> Bill wrote:
> >>> I'm using Drivewire 4 and nos96809l2v030300coco3_dw.dsk, and when
> >>> I try to access a physical drive, I get an ERROR 249 message. Does
> >>> anyone have a solution to this? I can format to the physical
> >>> drive, and after that, II get the ERROR 249 again
> >>
> >> Bill,
> >>
> >> That errors meaning can be found by entering error 249 You will get
> >> 249 - Wrong Type
> >> which at first glance won't mean much. Based on the sparse
> >> information you have supplied, it should mean that you don't have
> >> an OS-9 disk loaded in your "physical drive."
> >>
> >> Now you have said that you can format a physical drive, but how do
> >> you know that the format worked? Have you checked your drive
> >> descriptors with dmode? What is the exact nature of your system?
> >>
> >> Without more information about your system, there is no good way to
> >> provide useful information. I can say that with the disk you
> >> mentioned mounted in DW4 disk 0, and a floppy in one of my drives
> >> on a Coco3, I can read my floppy and not get a 249 error.
> >
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > https://pairlist5.pair.net/mailman/listinfo/coco

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
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