In article <5m6v44hq3vvs1am7k2i2lid6hlpq6fiqvm@4ax.com>, JW
<none@dev.null> writes
>>The 1772 did not use one.
>
>I was unable to find a datasheet for that device,
It's a Western Digital device, a development of the 1770. Also made
(under licence I assume) by VLSI. Popular in early home computers (BBC
Micro, Atari ST, Acorn Archimedes).
Previously Mike Tomlinson <mike@jasper.org.uk> wrote:
> In article <5m6v44hq3vvs1am7k2i2lid6hlpq6fiqvm@4ax.com>, JW
> <none@dev.null> writes
>>>The 1772 did not use one.
>>
>>I was unable to find a datasheet for that device,
> It's a Western Digital device, a development of the 1770. Also made
> (under licence I assume) by VLSI. Popular in early home computers (BBC
> Micro, Atari ST, Acorn Archimedes).
> Try searching for WD1770 or WD1772.
I think the WD1772 is an ATARI adaption of the WD1770. Anyways, its
one of the chips I really understood way back when I had an ATARI
ST. I have not done anything on that level with floppies since that
time.
On 14 Jun 2008 00:31:34 GMT, Arno Wagner <me@privacy.net> put finger
to keyboard and composed:
>Previously Mike Tomlinson <mike@jasper.org.uk> wrote:
>> In article <5m6v44hq3vvs1am7k2i2lid6hlpq6fiqvm@4ax.com>, JW
>> <none@dev.null> writes
>
>>>>The 1772 did not use one.
>>>
>>>I was unable to find a datasheet for that device,
>
>> It's a Western Digital device, a development of the 1770. Also made
>> (under licence I assume) by VLSI. Popular in early home computers (BBC
>> Micro, Atari ST, Acorn Archimedes).
>
>> Try searching for WD1770 or WD1772.
>
>I think the WD1772 is an ATARI adaption of the WD1770. Anyways, its
>one of the chips I really understood way back when I had an ATARI
>ST. I have not done anything on that level with floppies since that
>time.
>
>Arno
================================================== =================
The WD1771 is the first in a line of floppy disk controllers produced
by Western Digital.
The WD1771 was succeeded by many derivatives that were mostly
software-compatible:
The WD2791-WD2797 series added an internal data separator using an
analog phase-locked loop, with some external passive components
required for the VCO.
The WD1770, WD1772, and WD1773 used an internal digital data
separator, eliminating the need for external passive components. They
supported double density, despite the apparent regression of the part
number ...
================================================== =================
On 10 Jun 2008 13:10:48 GMT, Arno Wagner <me@privacy.net> put finger
to keyboard and composed:
>There is no PLL in a floppy controller.
The datasheet for the original PC AT FDC (NEC uPD765) talks about an
external phase locked loop, and the PC AT FDD/HDD controller circuits
designate uPD765 pin 24 as "VCO EN". In another post I have listed
several different FDC chips, some using an external analogue PLL,
others using an internal digital data separator. I have also found
patents which refer to the use of PLLs in FDC digital data separators.
Sheet 1 shows the Floppy Data Separator (D/S) control chip. Pins 5 & 6
appear to be the data rate select bits.
Sheet 4 shows NEC's uPD765 FD controller chip, and sheet 7 shows the
write control logic.
>> I haven't yet seen a controller that couldn't handle a
>> 720KB 3.5" drive. Its data rate is 2700 sectors per minute. A 360KB DD
>> 5.25" drive has the same number of sectors/track (9), and spins at the
>> same speed (300RPM). Therefore it has the same data rate and should be
>> electrically indistinguishable from a 720KB 3.5" drive (apart from a
>> lesser number of tracks). A 360KB diskette in a faster drive should
>> pose no problem since its data rate would fall in the middle of the
>> PLL's range. Of course I'm assuming that the controller doesn't have
>> two different PLLs, one for each drive type.
>
>Have a look at a floppy controller manual. You can set the clock
>divisor and it has to be set for the expected data rate in order
>for this to work.
Yes, you are correct. The original IBM AT BIOS supports four data
rates, 250Kbs, 300Kbs, 500Kbs, and "reserved". Selecting the wrong
data rate results in no read.
>You need it anyways, since writes cannot
>synchronize on anything.
I concede that writes appear to be executed in open loop mode,
although it is clear that the sync bytes determine when writing
starts. During formatting, however, there must be some reference
point, namely the index pulse.
>>>>>They are also 96tpi rather than 48tpi.
>
>> Not the early ones. They were definitely 48TPI.
>
>> See http://en.wikipedia.org/wiki/Floppy_disk
>
>> "Finally in 1983 DOS 2.0 supported 9 sectors per track rather than 8,
>> providing 180 KB on a (formatted) single-sided disk and 360 KB on a
>> double-sided."
>
>> Do the maths and you'll find that equates to 40 tracks per side.
>
>Are you sure there ever were drives for 40 tracks double sided?
The circuit diagram for IBM's PC AT double sided diskette drive shows
two R/W heads. The technical reference manual states that "the Double
Sided Diskette Drive is a direct-access device that can store
320/360Kb of data on a dual-sided 5-1/4 inch diskette". The source
listing for the AT BIOS refers to track numbers in the range of 0-39
for 320/360 media in a 320/360 drive, and sector numbers in the range
of 1-8/9.
The DOS help docs for the Format command list the following options:
================================================== ===============
/F:size
Specifies the size of the floppy disk to format. When possible,
use this switch instead of the /T and /N switches. Use one of the
following values for size:
160 (or 160K or 160KB)
160K, single-sided, double-density, 5.25-inch disk
180 (or 180K or 180KB)
180K, single-sided, double-density, 5.25-inch disk
320 (or 320K or 320KB)
320K, double-sided, double-density, 5.25-inch disk
360 (or 360K or 360KB)
360K, double-sided, double-density, 5.25-inch disk
720 (or 720K or 720KB)
720K, double-sided, double-density, 3.5-inch disk
1200 (or 1200K or 1200KB or 1.2 or 1.2M or 1.2MB)
1.2-MB, double-sided, quadruple-density, 5.25-inch disk
1440 (or 1440K or 1440KB or 1.44 or 1.44M or 1.44MB)
1.44-MB, double-sided, quadruple-density, 3.5-inch disk
2880 (or 2880K or 2880KB or 2.88 or 2.88M or 2.88MB)
2.88-MB, double-sided, extra-high-density, 3.5-inch disk
================================================== ===============
>> BTW I do have Nashua DSDD and DSQD 96TPI diskettes.
>
>So?? I have thrown away some 5.25" DSDD and DSHD (HD=QD)
>sisks too. Where is the problem here?
According to the above MS and IBM docs, DSDD implies 48TPI, and 96TPI
implies DSHD.
>>>> A 720KB 3.5" diskette rotating at 300RPM would produce a data rate of
>>>> 2700 sectors per minute. A 360KB diskette rotating at 360RPM would
>>>> produce a data rate of 3240 sectors per minute. A 1.44MB diskette
>>>> rotating at 300RPM would produce a data rate of 5400 sectors per
>>>> minute. Therefore it seems to me that a controller that can read a
>>>> 720KB 3.5" diskette should easily handle a 360KB 5.25" diskette, if
>>>> the issue is the range of the PLL/VCO in the clock/data separator.
>>>
>>>WIth a 5.25" DD drive, no problem at all. With a 5.25" HD
>>>drive, the 20% faster speed may just be within the range
>>>it can still syncronize on.
>
>> That would only be a problem if the controller used two different
>> PLLs. Otherwise it should be easier to sync with the faster drive. See
>> above.
>
>No PLL in an FDC. Not even a digital one.
>
>>> You cannot write though.
>
>> AFAICS, the same PLL is used for reading and writing. If you can do
>> one, then you can do the other.
>
>No PLL in an FDC.
>
>>>However
>>>a PC floppy controller can deal with 360rpm by increasing
>>>the speed of everything. You just need BIOS support and need
>>>to configure your drive as 5.25" HD.
>>>
>>>Arno
>
>> If you could spin your 3.5" drive at 360RPM, then your BIOS or OS
>> wouldn't know the difference.
>
>It would, sicne my disks would become unreadable.
>
>> In fact I just tried configuring my 1.44MB drive as a 1.2MB FD, and my
>> 1.2MB as a 1.44MB FD, and was still able to read 1.44MB and 1.2MB
>> diskettes in their respective drives.
>
>That is unsurprising. Both situations deliver the standard,
>2ms-clocked MFM signal that the controller expects per default with
>HD. You would have to put a 3.5" disk into the 5.25" drive so simulate
>the other thing. No adjustment for drive speed id needed with HD of
>either size.
I see now that the two diskette types would produce the same data
rate. Therefore my results support your contention that the data rate
has to be set in the controller to match the expected data rate from
the FD. I was wrong. Sorry.
>> However, I wasn't able to read a
>> 5.25" 360KB diskette when the 5.25" HD drive was configured as a
>> 1.44MB FD.
>
>And here is the problem that this gives a 3.3ms clocked MFM
>instead of a 4ms clocked one that is expected for a DD disk. The
>controller cannot handle a deviation this large. And since
>the drive was set to 3.5" no, test whether it actually was
>a 360rmp drive. You just proved my point.
>
>Arno
I agree.
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
On Sat, 07 Jun 2008 00:14:35 -0400, mm <NOPSAMmm2005@bigfoot.com> put
finger to keyboard and composed:
>A friend gave me a 5 1/4 inch floppy that she wants to retrieve some
>data from.
>Current attempts to read the disk with a high density drive have given
>nothing but low-values, zeroes, including when using Norton Diskedit
>(where I only read 12 clusters) and RESQFLPY, with which I copied the
>entire floppy and got a file 368,640 bytes long. When I looked at the
>copy on the hard drive, using Notepad+, it was entirely zeroes.
You could try loading the FDREAD.EXE DOS TSR that ships with FDFORMAT.
FDREAD allows your machine to read special high capacity formats which
are written by PC-compatible hardware.
Previously Franc Zabkar <fzabkar@iinternode.on.net> wrote:
> On 10 Jun 2008 13:10:48 GMT, Arno Wagner <me@privacy.net> put finger
> to keyboard and composed:
>>There is no PLL in a floppy controller.
> The datasheet for the original PC AT FDC (NEC uPD765) talks about an
> external phase locked loop, and the PC AT FDD/HDD controller circuits
> designate uPD765 pin 24 as "VCO EN". In another post I have listed
> several different FDC chips, some using an external analogue PLL,
> others using an internal digital data separator. I have also found
> patents which refer to the use of PLLs in FDC digital data separators.
> Sheet 1 shows the Floppy Data Separator (D/S) control chip. Pins 5 & 6
> appear to be the data rate select bits.
> Sheet 4 shows NEC's uPD765 FD controller chip, and sheet 7 shows the
> write control logic.
Yes, you are correct that there are FDCs with PLLs, as I have found
out by now. There are also those without and the one I studied in
detail way back did not have one. Sorry about my absolute statement.
>>> I haven't yet seen a controller that couldn't handle a
>>> 720KB 3.5" drive. Its data rate is 2700 sectors per minute. A 360KB DD
>>> 5.25" drive has the same number of sectors/track (9), and spins at the
>>> same speed (300RPM). Therefore it has the same data rate and should be
>>> electrically indistinguishable from a 720KB 3.5" drive (apart from a
>>> lesser number of tracks). A 360KB diskette in a faster drive should
>>> pose no problem since its data rate would fall in the middle of the
>>> PLL's range. Of course I'm assuming that the controller doesn't have
>>> two different PLLs, one for each drive type.
>>
>>Have a look at a floppy controller manual. You can set the clock
>>divisor and it has to be set for the expected data rate in order
>>for this to work.
> Yes, you are correct. The original IBM AT BIOS supports four data
> rates, 250Kbs, 300Kbs, 500Kbs, and "reserved". Selecting the wrong
> data rate results in no read.
>>You need it anyways, since writes cannot
>>synchronize on anything.
> I concede that writes appear to be executed in open loop mode,
> although it is clear that the sync bytes determine when writing
> starts.
They do.
> During formatting, however, there must be some reference
> point, namely the index pulse.
Yes, it is used for the track start.
>>>>>>They are also 96tpi rather than 48tpi.
>>
>>> Not the early ones. They were definitely 48TPI.
>>
>>> See http://en.wikipedia.org/wiki/Floppy_disk
>>
>>> "Finally in 1983 DOS 2.0 supported 9 sectors per track rather than 8,
>>> providing 180 KB on a (formatted) single-sided disk and 360 KB on a
>>> double-sided."
>>
>>> Do the maths and you'll find that equates to 40 tracks per side.
>>
>>Are you sure there ever were drives for 40 tracks double sided?
> The circuit diagram for IBM's PC AT double sided diskette drive shows
> two R/W heads. The technical reference manual states that "the Double
> Sided Diskette Drive is a direct-access device that can store
> 320/360Kb of data on a dual-sided 5-1/4 inch diskette". The source
> listing for the AT BIOS refers to track numbers in the range of 0-39
> for 320/360 media in a 320/360 drive, and sector numbers in the range
> of 1-8/9.
Convincing. I would have been satisfied with a ''yes'' ;-)
> The DOS help docs for the Format command list the following options:
> ================================================== ===============
> /F:size
> Specifies the size of the floppy disk to format. When possible,
> use this switch instead of the /T and /N switches. Use one of the
> following values for size:
> 160 (or 160K or 160KB)
> 160K, single-sided, double-density, 5.25-inch disk
Clearly 40 tracks. Agreed.
> 180 (or 180K or 180KB)
> 180K, single-sided, double-density, 5.25-inch disk
> 320 (or 320K or 320KB)
> 320K, double-sided, double-density, 5.25-inch disk
> 360 (or 360K or 360KB)
> 360K, double-sided, double-density, 5.25-inch disk
> 720 (or 720K or 720KB)
> 720K, double-sided, double-density, 3.5-inch disk
Ok, I think I see what the issue is: 3.5" DD is 80 tracks while
5.25" DD is 40 tracks. Seems my memory is a bit fuzzy after all
this time.
> 1200 (or 1200K or 1200KB or 1.2 or 1.2M or 1.2MB)
> 1.2-MB, double-sided, quadruple-density, 5.25-inch disk
> 1440 (or 1440K or 1440KB or 1.44 or 1.44M or 1.44MB)
> 1.44-MB, double-sided, quadruple-density, 3.5-inch disk
> 2880 (or 2880K or 2880KB or 2.88 or 2.88M or 2.88MB)
> 2.88-MB, double-sided, extra-high-density, 3.5-inch disk
> ================================================== ===============
>>> BTW I do have Nashua DSDD and DSQD 96TPI diskettes.
>>
>>So?? I have thrown away some 5.25" DSDD and DSHD (HD=QD)
>>sisks too. Where is the problem here?
> According to the above MS and IBM docs, DSDD implies 48TPI, and 96TPI
> implies DSHD.
On 5.25" floppies. On 3.5" floppies DD is 80 tracks.
>>>>> A 720KB 3.5" diskette rotating at 300RPM would produce a data rate of
>>>>> 2700 sectors per minute. A 360KB diskette rotating at 360RPM would
>>>>> produce a data rate of 3240 sectors per minute. A 1.44MB diskette
>>>>> rotating at 300RPM would produce a data rate of 5400 sectors per
>>>>> minute. Therefore it seems to me that a controller that can read a
>>>>> 720KB 3.5" diskette should easily handle a 360KB 5.25" diskette, if
>>>>> the issue is the range of the PLL/VCO in the clock/data separator.
>>>>
>>>>WIth a 5.25" DD drive, no problem at all. With a 5.25" HD
>>>>drive, the 20% faster speed may just be within the range
>>>>it can still syncronize on.
>>
>>> That would only be a problem if the controller used two different
>>> PLLs. Otherwise it should be easier to sync with the faster drive. See
>>> above.
>>
>>No PLL in an FDC. Not even a digital one.
>>
>>>> You cannot write though.
>>
>>> AFAICS, the same PLL is used for reading and writing. If you can do
>>> one, then you can do the other.
>>
>>No PLL in an FDC.
>>
>>>>However
>>>>a PC floppy controller can deal with 360rpm by increasing
>>>>the speed of everything. You just need BIOS support and need
>>>>to configure your drive as 5.25" HD.
>>>>
>>>>Arno
>>
>>> If you could spin your 3.5" drive at 360RPM, then your BIOS or OS
>>> wouldn't know the difference.
>>
>>It would, sicne my disks would become unreadable.
>>
>>> In fact I just tried configuring my 1.44MB drive as a 1.2MB FD, and my
>>> 1.2MB as a 1.44MB FD, and was still able to read 1.44MB and 1.2MB
>>> diskettes in their respective drives.
>>
>>That is unsurprising. Both situations deliver the standard,
>>2ms-clocked MFM signal that the controller expects per default with
>>HD. You would have to put a 3.5" disk into the 5.25" drive so simulate
>>the other thing. No adjustment for drive speed id needed with HD of
>>either size.
> I see now that the two diskette types would produce the same data
> rate. Therefore my results support your contention that the data rate
> has to be set in the controller to match the expected data rate from
> the FD. I was wrong. Sorry.
No problem. This is a rather subtle point and I took some time
back then to understand it myself. I tried to connect a 5.25"
HD floppy to my Atari ST and never got it to work right.
>>> However, I wasn't able to read a
>>> 5.25" 360KB diskette when the 5.25" HD drive was configured as a
>>> 1.44MB FD.
>>
>>And here is the problem that this gives a 3.3ms clocked MFM
>>instead of a 4ms clocked one that is expected for a DD disk. The
>>controller cannot handle a deviation this large. And since
>>the drive was set to 3.5" no, test whether it actually was
>>a 360rmp drive. You just proved my point.
>>
>>Arno
Re: How to play an old floppy disk. 
Linear Mode
