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Apple 5.25" drive vs Unidisk 5.25"

What are the differences between these drives apart from the Unidisk
requiring 12v ?


0
rob9165 (18)
6/24/2006 6:15:58 AM
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rob wrote:
> What are the differences between these drives apart from the Unidisk
> requiring 12v ?

There isn't any difference, except daisy-chain cabling and the case.

Both require +12v., +5v, and -12v.

-michael

Parallel computing for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."
0
mjmahon (7061)
6/24/2006 7:31:24 AM
Michael J. Mahon wrote:
> rob wrote:
> > What are the differences between these drives apart from the Unidisk
> > requiring 12v ?
>
> There isn't any difference, except daisy-chain cabling and the case.
>
> Both require +12v., +5v, and -12v.

??

The UniDisk 5.25" had daisy chaining as well, no ? How else did one add
a second drive?

0
mdj.mdj (1102)
6/24/2006 10:49:07 AM
In <0tGdnaAuM5HTdwHZnZ2dnUVZ_uqdnZ2d@comcast.com> Michael J. Mahon wrote:
> rob wrote:
>> What are the differences between these drives apart from the Unidisk
>> requiring 12v ?
> 
> There isn't any difference, except daisy-chain cabling and the case.
> 
> Both require +12v., +5v, and -12v.
> 
> -michael

Hmm... I remembered reading that the reason the Apple IIe card for the 
Macintosh LC could only use the Apple 5.25 Drive for its 5.25" drive was 
that the Mac LC didn't have a -12V supply.

This article claims that's the reason.
Apple IIe Card: Which Drives are Supported
http://docs.info.apple.com/article.html?artnum=8807

But then this one says the drive does need -12V.
Apple 5.25 Drive: Specifications
http://docs.info.apple.com/article.html?artnum=7886

But then again maybe it's just an incorrect copy and paste of the 
specifications of the older drive.
UniDisk: Specifications (Discontinued)
http://docs.info.apple.com/article.html?artnum=1189

I suppose I could satisfy my curiosity by opening up one of those Apple 
5.25 Drives by my feet...

-- 
* Roger Johnstone, Invercargill, New Zealand -> http://roger.geek.nz
* PS/2 Mouse Adapter for vintage Apple II or Mac
* SCART RGB cable for Apple IIGS
0
news2006 (141)
6/24/2006 11:25:40 AM
mdj wrote:
> Michael J. Mahon wrote:
> 
>>rob wrote:
>>
>>>What are the differences between these drives apart from the Unidisk
>>>requiring 12v ?
>>
>>There isn't any difference, except daisy-chain cabling and the case.
>>
>>Both require +12v., +5v, and -12v.
> 
> 
> ??
> 
> The UniDisk 5.25" had daisy chaining as well, no ? How else did one add
> a second drive?

I thought we were comparing the Disk ][ and the Unidisk 5.25"...

-michael

Parallel computing for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."
0
mjmahon (7061)
6/24/2006 6:03:47 PM
Roger Johnstone wrote:
> In <0tGdnaAuM5HTdwHZnZ2dnUVZ_uqdnZ2d@comcast.com> Michael J. Mahon wrote:
> 
>>rob wrote:
>>
>>>What are the differences between these drives apart from the Unidisk
>>>requiring 12v ?
>>
>>There isn't any difference, except daisy-chain cabling and the case.
>>
>>Both require +12v., +5v, and -12v.
>>
>>-michael
> 
> 
> Hmm... I remembered reading that the reason the Apple IIe card for the 
> Macintosh LC could only use the Apple 5.25 Drive for its 5.25" drive was 
> that the Mac LC didn't have a -12V supply.
> 
> This article claims that's the reason.
> Apple IIe Card: Which Drives are Supported
> http://docs.info.apple.com/article.html?artnum=8807
> 
> But then this one says the drive does need -12V.
> Apple 5.25 Drive: Specifications
> http://docs.info.apple.com/article.html?artnum=7886
> 
> But then again maybe it's just an incorrect copy and paste of the 
> specifications of the older drive.
> UniDisk: Specifications (Discontinued)
> http://docs.info.apple.com/article.html?artnum=1189
> 
> I suppose I could satisfy my curiosity by opening up one of those Apple 
> 5.25 Drives by my feet...

Actually, the only thing that -12v was *ever* used for was to allow a
bias adjustment for the head amplifier to go both positive and negative.

If Apple switched to a different head amplifier than the MC3740 (?),
they could have dispensed with the -12v supply.

-michael

Parallel computing for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."
0
mjmahon (7061)
6/24/2006 6:10:56 PM
Michael J. Mahon wrote:
> rob wrote:
> > What are the differences between these drives apart from the Unidisk
> > requiring 12v ?
>
> There isn't any difference, except daisy-chain cabling and the case.

There is a difference if you have a ROM03 IIgs...

See
http://groups.google.com.au/group/comp.sys.apple2/browse_frm/thread/764f115858dc29bb/0521a9adf824f50c?lnk=st&q=5.25+rom03+smartport&rnum=2&hl=en#0521a9adf824f50c

0
mcs6502 (519)
6/24/2006 11:15:07 PM
David Wilson wrote:
> Michael J. Mahon wrote:
> 
>>rob wrote:
>>
>>>What are the differences between these drives apart from the Unidisk
>>>requiring 12v ?
>>
>>There isn't any difference, except daisy-chain cabling and the case.
> 
> 
> There is a difference if you have a ROM03 IIgs...
> 
> See
> http://groups.google.com.au/group/comp.sys.apple2/browse_frm/thread/764f115858dc29bb/0521a9adf824f50c?lnk=st&q=5.25+rom03+smartport&rnum=2&hl=en#0521a9adf824f50c

That's *very* interesting, since the drive is just hardware.  ;-)

There must be some line used for smartport signalling that it leans
on too hard...?  Since it apparently *works* with the ROM01, it could
be a signal loading issue, where the ROM3 tightened the timing...or
what?

-michael

Parallel computing for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."
0
mjmahon (7061)
6/25/2006 12:20:14 AM
Michael J. Mahon wrote:
> That's *very* interesting, since the drive is just hardware.  ;-)
>
> There must be some line used for smartport signalling that it leans
> on too hard...?  Since it apparently *works* with the ROM01, it could
> be a signal loading issue, where the ROM3 tightened the timing...or
> what?

I wish I could recall where I found this information originally. I am
sure it was a software change in the ROM03 firmware.
I think (but am not sure) that there may be an extra chip on the Apple
5.25 drive PCB that is not present on the UniDisk 5.25. As for the
DuoDisk, I do not know if it works the same way or not. I have an Apple
5.25 and a DuoDisk and both ROM01 and ROM03 IIgs systems. I will have
to test this.

0
mcs6502 (519)
6/25/2006 4:08:22 AM
Michael J. Mahon wrote:

> I thought we were comparing the Disk ][ and the Unidisk 5.25"...

Although now that I look in my parts box, I have one Unidisk 5.25" that
doesn't have a daisy chain port... curous, I wonder if it's actually
there behind the plate...

Matt

0
mdj.mdj (1102)
6/25/2006 5:18:42 AM
David Wilson wrote:
> Michael J. Mahon wrote:
> 
>>That's *very* interesting, since the drive is just hardware.  ;-)
>>
>>There must be some line used for smartport signalling that it leans
>>on too hard...?  Since it apparently *works* with the ROM01, it could
>>be a signal loading issue, where the ROM3 tightened the timing...or
>>what?
> 
> 
> I wish I could recall where I found this information originally. I am
> sure it was a software change in the ROM03 firmware.
> I think (but am not sure) that there may be an extra chip on the Apple
> 5.25 drive PCB that is not present on the UniDisk 5.25. As for the
> DuoDisk, I do not know if it works the same way or not. I have an Apple
> 5.25 and a DuoDisk and both ROM01 and ROM03 IIgs systems. I will have
> to test this.

It would be interesting to know.

I've always regarded the various generations of Apple 5.25" disk drives
as an exercise in repackaging.  ;-)

-michael

Parallel computing for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."
0
mjmahon (7061)
6/25/2006 8:30:48 AM
Roger Johnstone wrote:
> I suppose I could satisfy my curiosity by opening up one of those Apple
> 5.25 Drives by my feet...

There's a handy list of drive compatibility here:
http://www.mandrake.demon.co.uk/Apple/drives.html

Looks like I need an Apple 5.25 to use on both my //c & Mac IIe card.

Cheers,
Nick.

0
6/25/2006 5:49:27 PM
> There must be some line used for smartport signalling that it leans
> on too hard...?  Since it apparently *works* with the ROM01, it could
> be a signal loading issue, where the ROM3 tightened the timing...or
> what?

Here is another reference:
http://www.apple2.org/A2WebRef/A2Reference03.html

ROM03, IIc+ and IIe emulation card all require Apple 5.25 drives rather
than UniDisk 5.25.

I note that this set of machines represents the final Apple II
Smartport implementations.

0
mcs6502 (519)
6/25/2006 11:51:19 PM
Michael J. Mahon wrote:
> That's *very* interesting, since the drive is just hardware.  ;-)
>
> There must be some line used for smartport signalling that it leans
> on too hard...?  Since it apparently *works* with the ROM01, it could
> be a signal loading issue, where the ROM3 tightened the timing...or
> what?

I finally found where I read about this:
http://www.apple2.org/A2WebRef/A2Reference05.html

0
mcs6502 (519)
6/26/2006 12:45:18 AM
David Wilson wrote:
> Michael J. Mahon wrote:
> 
>>That's *very* interesting, since the drive is just hardware.  ;-)
>>
>>There must be some line used for smartport signalling that it leans
>>on too hard...?  Since it apparently *works* with the ROM01, it could
>>be a signal loading issue, where the ROM3 tightened the timing...or
>>what?
> 
> 
> I finally found where I read about this:
> http://www.apple2.org/A2WebRef/A2Reference05.html

So Apple *did* abandon compatibility with their older 5.25" drives!

Actually pretty amazing, since they got so little for such a big
backward compatibility hit.

-michael

Parallel computing for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."
0
mjmahon (7061)
6/26/2006 6:16:48 AM
Reply: