8" drive on PC troubleshooting

[Randy McLaughlin]

From: "Vintage Computer Festival" <vcf at siconic.com>
Sent: Friday, March 04, 2005 10:08 PM
> On Wed, 2 Mar 2005, Dwight K. Elvey wrote:
>
>> Hi
>>  Made a mistake and left out part of the pointer.
>> The first one should have been:
>>
>> http://members.tripod.com/~oldboard/assembly/bios_data_area.html
>>
>>  Hope this didn't cause any great confusion.
>> Dwight
>>
>> PS Thanks to Robert Greenstreet for pointing this out.
>
> Ok, so I used debug to change the byte at 50:22 from DF to D1.  No go.  I
> then tried D0: no go.  I can only assume I'm doing something wrong.
>
> Has anyone ever actually successfully hooked an 8" drive to a PC
> controller and gotten it to work?  If so, who is that person?
>
> -- 
>
> Sellam Ismail                                        Vintage Computer 
> Festival
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>
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I've done it and have never had any trouble.  I use a Compaq P100 since it 
handles FM & a Mitsubishi 1/2 height 8" drive.

I've only used it with 22disk, Teledisk, and Anadisk.  They all work fine 
but 22disk has to be v1.41, later versions do not work with 8" drives.

A few things to remember when dealing with classic disks on PC's:

Use a real DOS not a DOS window.

Make sure drive is OK (clean it & run RPM tests).

Make sure your computer handles the format, 8" drives use the same data 
transfer rate as PC HD drives and standard PC controllers (8 bit 360K 
controllers) will not handle 8" drives.  Most PC controllers don't handle 
FM.

Get 22disk v1.41 and try some 8" MFM formats (format, write, read back). 
Only try FM (such as SSSD) after you have MFM working.

Double check your cable.

The TG43 signal can be ignored until you have a problem.  No matter what the 
first half of the disk should always be OK.


I am working on creating a page with drive info similar to Herb Johnson's 
but more oriented to cleaning and hooking up to PC's.


Here are a couple of links to check out:

http://home.iae.nl/users/pb0aia/cm/8-525.html

http://nemesis.lonestar.org/computers/tandy/hardware/model16_6000/floppyfix.html


The TG43 signal is used by truly old 8" drives.  Most 8" drives ignore it. 
The problem was handles by having "smarter" floppy drives.  Early 8" drives 
were built with discrete logic and mediocre heads later they used LSI chips 
and better heads.  The newer 8" drives "knew" when to change the head 
current rather than relying on the host controller.

If you have trouble with the outer tracks (it is a writing problem) then you 
can buy a board from dbit to generate the TG43 signal.



Randy
www.s100-manuals.com