Subject: Re: myarc fdc card revisions & DSR EPROM versions

From: "Tony Knerr" <[email-masked]>
Date: Sun, 27 Jan 2013 11:33:44 -0000

Just a shot in the dark, but the difference might be that one of the
versions increases the file size by a sector when copying from single or double density to quad, as it should on a file that ends with an odd number of sector data. But the filesize is not reduced when copying back. I know I had one of those beasts in the past.

Tony

--- In [email-masked], Insane Multitasker  wrote:
>
> 
> Today I finished some repairs and had the chance to have two Myarc FDCs side by side.  I noticed the first card had an extra diode and when I inspected the second card, found a diode had been added and a second unrelated trace had been modified.  Secondly, in comparing with one of my own cards, I found I have a DSR EPROM v1.6 PC, Q1770.
>  
> 1.  Does anyone recall an article describing the card revision changes to the Myarc FDC?
> 2.  Does anyone know how v1.6 might differ from the v1.5 that is more prevalent?  I recall Tony MdGovern writing about some quirks with Quad density file problems in one of the revisions but can't seem to find any revision history for the DSR.
>  
> Tim
>

---

From: Insane Multitasker <[email-masked]>
Date: Sun, 27 Jan 2013 11:57:24 -0600

Yes, that's the problem I was thinking of. 
 
The v1.5 EPROM/DSR is the version Richard and I have been installing.  I doubt it has the bug, so does that mean 1.6 is another enhancement or bug fix...?   This is like playing Trivial Pursuit... :)

> To: [email-masked]
> From: [email-masked]
> Date: Sun, 27 Jan 2013 11:33:44 +0000
> Subject: [TI994A] Re: myarc fdc card revisions & DSR EPROM versions
> 
> ------------------------------------
> 
> Yahoo! Groups Links
> 
> 
>

---

From: "Paolo Bagnaresi" <[email-masked]>
Date: Sun, 27 Jan 2013 21:28:29 +0100

Hi Tony and everybody!

To fix the bug, in 1987, I developped 80TK-FIXER.

80TK-FIXER  can be found on:
ftp://ftp.whtech.com/user%20groups/Cedar%20Valley/library/CV317.DSK

Here's the explanation of the 80 Track Eprom Bug.

80TK-FIXER
This program, besides providing a disk catalog, will fix the "bug" of 80
Track Eprom version >03. This Eprom, when saving a DIS/VAR, DIS/FIX,
INT/VAR, INT/FIX file makes an error in determining the total sectors used
by the file. This info is stored in the Directory sector where the 
FILENAME
is kept, offset >0E from the beginning of the sector. All other values in
the same sector are correct. Even the bit map free/used sector in sector
zero is correct. However, >0E word in filename sector is sometimes 
different
from what it should be.

More precisely, if the REALLY Total used sectors are an even number, then
 >0E word (total sector) reports 1 sector less. On the other hand, if real
total sectors is an odd number, then >0E sector is correct. This bug will
not usually give you any problem: the file is still redable (TI-Writer, 
Ext.
Basic...), since >0E word (total sector) is not used in direct file
handling.

However, when you try to copy that file to another disk, with a logical
filename copier, then the last sector WILL NOT BE COPIED, if the total # 
of
sector is even! So, the same file will not be readable any longer in the
copy disk by TI-Writer, Ext. Basic, E/A...., since the last sector is now
REALLY MISSING! Only a sector-to-sector copy will give you a readable 
file.

As far as 80 Track Eprom version >03 is concerned, please note the
following:
1) Files saved first to RAM-DISK will be correct.
2) Files saved first to SS/SD or DS/DD diskettes (not 80 Track), will be
correct.

3) Files that are correct, when copied to an 80 track disk by Myarc Disk
Manager Supreme, DM1000 (Ottawa UG), BA-COPIER or any other logical 
copier,
will be correct.

4) Program files (memory image files) will always be correct, even when
saved directly to an 80 track disk.

5) Troubles may happen only when saving a file, record by record, DIRECTLY
to an 80 track disk, as it would happen with TI-WRITER or Editor of E/A.

To avoid this bug, 80TK-FIXER was created. You should use it from time to
time, only when you save a file directly to the diskette. 80TK-FIXER will
fix any bugged file, by calculating exactly how many sectors will be 
really
used by the file. Then, this new # will be poked into >0E word (total
sectors) of the FILENAME sector. 80TK-FIXER is really fast. You will not
notice the difference in cataloging speed from any other disk cataloger
program.
If the FIX 80 TRACK DISKETTE Otpion is used, you will see a "Wrong" on the
right of the screen row 4 (Pr.Name, Sector Type, Lenght, P, Wrong). If a
bugged file is found, then a "Y" will appear below the "Wrong" header, on
the corresponding screen row. Thereafter, that FILENAME Sector will be
fixed.

After 80TK-FIXER has finished, you will be given a message, either:

"All wrong files have been fixed" or

"No wrong file has been found", depending on what happened previously.

Also, you will notice that, after fixing, the wrong file will increase its
sector size by at least 1 sector. You will check that by re-cataloging 
again
the same diskette.

After fixing, the diskette can be backed with any logical file copy 
program.

Warning: use of 80TK-FIXER on a back-up diskette will work only if the
back-up has been obtained by a sector-to-sector copy (because only in this
case the back-up diskette will contain all the physical sectors the file 
is
made of).

You are strongly suggested to use 80TK-FIXER before copying a file from an
80 track diskette. We all hope that Myarc will release a new Eprom to fix
the above bug. Then, 80TK-FIXER will be useless. I hope it will happen 
soon!

March 1987 version, New Horizon Ram Disk compatible.

>
> ----- Original Message ----- 
> From: "Tony Knerr" <[email-masked]>
> To: <[email-masked]>
> Sent: Sunday, January 27, 2013 12:33 PM
> versions increases the file size by a sector when copying from single or
> double density to quad, as it should on a file that ends with an odd
> number of sector data. But the filesize is not reduced when copying 
> back.
> I know I had one of those beasts in the past.
>
> Tony
>
>> Today I finished some repairs and had the chance to have two Myarc FDCs
>> side by side.  I noticed the first card had an extra diode and when I
>> inspected the second card, found a diode had been added and a second
>> unrelated trace had been modified.  Secondly, in comparing with one of 
>> my
>> own cards, I found I have a DSR EPROM v1.6 PC, Q1770.
>>
>> 1.  Does anyone recall an article describing the card revision changes 
>> to
>> the Myarc FDC?
>> 2.  Does anyone know how v1.6 might differ from the v1.5 that is more
>> prevalent?  I recall Tony MdGovern writing about some quirks with Quad
>> density file problems in one of the revisions but can't seem to find 
>> any
>> revision history for the DSR.
>>
>> Tim
>>
>
>
>