Re: Now have a 8280 formatted 8" disk (success!)

From: Rob Clarke <>
Date: Thu, 16 Feb 2017 00:31:56 +0100
Message-ID: <>
Woo-hoo! It works. :-)

Following Mike S's comment I made my punched hole a bit bigger and now 
it's formatting successfully, but wow it is slow! It takes around 12 
minutes and 40 seconds to complete, so several times longer than a 1541. 
It  seems to be a 2 pass format process. The first pass is quite fast, 
taking about 20 seconds to step through the 77 tracks, but the second 
pass is very slow, taking around 9 seconds per track. I seem to remember 
reading somewhere that tha BAM maps out bad sectors, so I'm guessing 
that the second pass is checking for bad sectors. When it completes the 
second pass, the head steps backwards and forwards several times before 
finally finishing.

Also, it takes a very long time the first time you read the directory 
with the head stepping several times, but whern it does I get:

0 "test disk            " 99 3a

3946 blocks free.

So the main finding from this is that it must be a double sided disk, if 
you use a single sided, it will fail with a read error.

cheers, Rob

On 15/02/2017 22:54, Mike Stein wrote:
> ----- Original Message -----
> From: "Rob Clarke" <>
> To: <>
> Sent: Wednesday, February 15, 2017 3:41 PM
> Subject: Re: Need an 8280 formatted 8" disk (progress!)
>> ...The 8280 needs double sided disks, as it explicitly says
>> "Double sided diskettes must be used and must be formatted with the
>> HEADER command before using for system operation. "at the beginning of
>> section 4 on the CBM_8280_Specifications.pdf document on your site Bo.
> Yeah, what confused me was this spec, also on Bo's site:
> Model    : 8280
> Type     : Dual 8" Floppy Disk
> Media    : Single Sided, Double Density
> Capacity : 1024K per disk, or 2048K total
> Interface: IEEE-488
> Dos      : CBM DOS 3.0
> Notes    : Huuuuuugggggggeeee!!!!> I tried last night to cut my own index hole using a google
>> image of a double sided disk as a measurement reference, but failed. :-(
> Maybe try making it a little larger in case it's misaligned a bit? Size is not really critical as long as the index sensor can see the LED.
>> Mike S., the drives in my 8280 are TM848-2's, which are the double sided
>> ones but which are *not* MPU controlled, like the 828-1E and 828-2E.
> That's what I assumed from looking at Andre's picture, but the specs and users manual on Bo's site are for the 848-E.
> Good luck!
> m
>> cheers, Rob
>> On 15/02/2017 21:01, Mike Naberezny wrote:
>>> On 2/15/17 11:20 AM, Bo Zimmerman wrote:
>>>> The disk also has a write-protect tab on the bottom-right of the
>>>> disk, near
>>>> where the read/write exposure strip is.  Came right out of the damn
>>>> box that
>>>> way.  Could the write-protect logic on 8" disks be opposite to 5.25"?
>>>> That is,
>>>> write is enabled when the tab is covered, and disabled when exposed?
>>> Yes.  The write protect notch on 8" disks has the opposite behavior of
>>> 5.25" disks.  I recently repaired a CGRS Microtech PEDISK II 8" disk
>>> system for PET.  I had to work through the same issues with the index
>>> hole location and write protect notch.
>>> Now that my PEDISK II system is working, I can provide a known good 8"
>>> single sided, soft sectored, single density (FM) formatted disk with
>>> 77 tracks, 26 sectors per track, and a 128 byte sector length.  Disks
>>> from my system have been successfully read on another.  The filesystem
>>> is not be compatible with CBM drives but the disk can be used to test
>>> sector read and write.
>>> Regards,
>>> Mike
>>        Message was sent through the cbm-hackers mailing list
>         Message was sent through the cbm-hackers mailing list

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Received on 2017-02-16 00:00:02

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