Re: Reading Commodore 900 disks in the 8250 (LP)

From: Francesco Messineo <francesco.messineo_at_gmail.com>
Date: Thu, 11 Jan 2024 14:03:08 +0100
Message-ID: <CAESs-_xoczvX8aakaLiYeDLwn-sG89LePnPqKsfROEQ8vbc0mA_at_mail.gmail.com>
On Thu, Jan 11, 2024 at 1:58 PM Santo Nucifora <santo.nucifora_at_gmail.com> wrote:
>
> Just to clarify:
>
> The 8250/SFD-1001 uses a Matsushita JU-570 or JU-570-2 drive mech.  The C900 uses a JA-560-012 drive mech and the serial number on mine is in the 100s.  I have never seen another drive in the wild.  Other than the C900 documentation, I have not been able to find any other info on these drives.

according to this document:
https://retrocmp.de/fdd/panasonic/Panasonic_JU-475-4_Service_Manual_OCR.pdf
The JA-560 is a 96 TPI drive
Frank IZ8DWF


>
> Hope this helps.
> Santo
>
>
>
> On Thu, Jan 11, 2024 at 7:15 AM Francesco Messineo <francesco.messineo_at_gmail.com> wrote:
>>
>> On Thu, Jan 11, 2024 at 1:04 PM Michal Pleban <lists_at_michau.name> wrote:
>> >
>> > Hello!
>> >
>> > Francesco Messineo wrote on 10.01.2024 16:45:
>> >
>> > > according to this page
>> > > https://www.zimmers.net/cbmpics/c900.html
>> > > The 900 has a 96 tpi floppy drive, the 8250 has (for sure) 100 tpi
>> > > drives.
>> >
>> > I am not entirely sure that this info is correct (see how it also says
>> > it's 1.2 MB whereas the disks have in fact 1.0 MB capacity). I do know
>> > that the disk drive interface is identical to the one used in the
>> > 8250LP. The C900 documentation states that MFM support is incomplete,
>> > and only GCR is used in the disk controller code, so they would not need
>> > to bother with 96 TPI MFM disks. The C900 mech is also outwardly
>> > identical to the one from the 8250LP except it has a grey faceplate, so
>> > I think there's good chance it is simply the same 100 TPI mech.
>> >
>>
>> if it supports only GCR (I assume the same format as the 8250?) then
>> why you need
>> to bother with MFM ?
>> If you know the actual format used it's easy to tell what is the
>> mechanism they used, if it's 80 tracks per side, then it's 96 TPI, if
>> it's 77 tracks per side, then it's 100 TPI.
>> Frank
>> > Regards,
>> > Michau.
>> >
>>
Received on 2024-01-11 15:00:03

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