Hi all,
I have an Advantest network analyser that uses a Teac FD-235GF 3156-U floppy
drive. Teac cannot/willnot provide any information on the drive or a
suitable teac replacement. They tell me it's a proprietary drive and to
contact Advantest. Advantest won't help either, the analyser is past service
support life.

Anyone have a collection of NOS or even used FD-235GF 3156-U drives I can
buy ( want around 3-5)

Or - anyone have any info on the teac 235-gf apart from the teac.jp website
glossy and any knowledge of a suitable replacement?

If I can determine what the jumper settings mean perhaps I can find another
drive that would suit. Anyone have a copy of the service manual for the
drive that identifies the jumper settings?

The jumper configuration for the drive as installed in the 3762ah is per the
following list.
A1-B1,B4-C4,B3-C3,D4-E4, F1-G1
D1-D2, E2-E3, G3-G4

Any help appreciated

Thanks
Greg

gcd wrote:

Hi all,
I have an Advantest network analyser that uses a Teac FD-235GF 3156-U
floppy
drive. Teac cannot/willnot provide any information on the drive or a
suitable teac replacement. They tell me it's a proprietary drive and
to contact Advantest. Advantest won't help either, the analyser is
past service support life.

Anyone have a collection of NOS or even used FD-235GF 3156-U drives I
can buy ( want around 3-5)

Or - anyone have any info on the teac 235-gf apart from the teac.jp
website glossy and any knowledge of a suitable replacement?

If I can determine what the jumper settings mean perhaps I can find
another drive that would suit. Anyone have a copy of the service
manual for the drive that identifies the jumper settings?

The jumper configuration for the drive as installed in the 3762ah is
per the following list.
A1-B1,B4-C4,B3-C3,D4-E4, F1-G1
D1-D2, E2-E3, G3-G4

Any help appreciated

Thanks
Greg

That could just be a standard PC floppy drive. Teac FD-235's are/used to
be used in IBM compatible PC's. I'm sure I have some kicking around.
I'll have a look on Monday when I get into work.

--
Best Regards:
Baron.

"Baron" wrote in message
...
gcd wrote:

Hi all,
I have an Advantest network analyser that uses a Teac FD-235GF 3156-U
floppy
drive. Teac cannot/willnot provide any information on the drive or a
suitable teac replacement. They tell me it's a proprietary drive and
to contact Advantest. Advantest won't help either, the analyser is
past service support life.

Anyone have a collection of NOS or even used FD-235GF 3156-U drives I
can buy ( want around 3-5)

Or - anyone have any info on the teac 235-gf apart from the teac.jp
website glossy and any knowledge of a suitable replacement?

If I can determine what the jumper settings mean perhaps I can find
another drive that would suit. Anyone have a copy of the service
manual for the drive that identifies the jumper settings?

The jumper configuration for the drive as installed in the 3762ah is
per the following list.
A1-B1,B4-C4,B3-C3,D4-E4, F1-G1
D1-D2, E2-E3, G3-G4

Any help appreciated

Thanks
Greg

That could just be a standard PC floppy drive. Teac FD-235's are/used to
be used in IBM compatible PC's. I'm sure I have some kicking around.
I'll have a look on Monday when I get into work.

--
Best Regards:
Baron.


Hi Baron,
the PC drives are FD-235 HF not GF as far as I've been able to identify and
the jumper set is different.

For the most part I reckon all I need is to know the jumper matrix settings,
from there I should be able to sort out modifying any current drive to suit.

However, if you do find some GF drives I would be most interested.

Thanks for the help
Greg

"Baron" wrote in message
...
gcd wrote:

Hi all,
I have an Advantest network analyser that uses a Teac FD-235GF 3156-U
floppy
drive. Teac cannot/willnot provide any information on the drive or a
suitable teac replacement. They tell me it's a proprietary drive and
to contact Advantest. Advantest won't help either, the analyser is
past service support life.

Anyone have a collection of NOS or even used FD-235GF 3156-U drives I
can buy ( want around 3-5)

Or - anyone have any info on the teac 235-gf apart from the teac.jp
website glossy and any knowledge of a suitable replacement?

If I can determine what the jumper settings mean perhaps I can find
another drive that would suit. Anyone have a copy of the service
manual for the drive that identifies the jumper settings?

The jumper configuration for the drive as installed in the 3762ah is
per the following list.
A1-B1,B4-C4,B3-C3,D4-E4, F1-G1
D1-D2, E2-E3, G3-G4

Any help appreciated

Thanks
Greg

That could just be a standard PC floppy drive. Teac FD-235's are/used to
be used in IBM compatible PC's. I'm sure I have some kicking around.
I'll have a look on Monday when I get into work.

--
Best Regards:
Baron.


Hi Baron,
the PC drives are FD-235 HF not GF as far as I've been able to identify and
the jumper set is different.

For the most part I reckon all I need is to know the jumper matrix settings,
from there I should be able to sort out modifying any current drive to suit.

However, if you do find some GF drives I would be most interested.

Thanks for the help
Greg

"gcd" wrote in message
...

"Baron" wrote in message
...
gcd wrote:

Hi all,
I have an Advantest network analyser that uses a Teac FD-235GF 3156-U
floppy
drive. Teac cannot/willnot provide any information on the drive or a
suitable teac replacement. They tell me it's a proprietary drive and
to contact Advantest. Advantest won't help either, the analyser is
past service support life.

Anyone have a collection of NOS or even used FD-235GF 3156-U drives I
can buy ( want around 3-5)

Or - anyone have any info on the teac 235-gf apart from the teac.jp
website glossy and any knowledge of a suitable replacement?

If I can determine what the jumper settings mean perhaps I can find
another drive that would suit. Anyone have a copy of the service
manual for the drive that identifies the jumper settings?

The jumper configuration for the drive as installed in the 3762ah is
per the following list.
A1-B1,B4-C4,B3-C3,D4-E4, F1-G1
D1-D2, E2-E3, G3-G4

Any help appreciated

Thanks
Greg

That could just be a standard PC floppy drive. Teac FD-235's are/used to
be used in IBM compatible PC's. I'm sure I have some kicking around.
I'll have a look on Monday when I get into work.

--
Best Regards:
Baron.


Hi Baron,
the PC drives are FD-235 HF not GF as far as I've been able to identify and
the jumper set is different.

For the most part I reckon all I need is to know the jumper matrix settings,
from there I should be able to sort out modifying any current drive to suit.

However, if you do find some GF drives I would be most interested.

Thanks for the help
Greg

***
Do any of these help?

http://www.teac.com/DSPD/pdf/3fd0105a.pdf

http://www.google.com.au/search?num=...G=Search&meta=

http://www.hkinventory.com/public/Of...=0&datecode =

Larry

"Larry" wrote in message
u...

"gcd" wrote in message
...

"Baron" wrote in message
...
gcd wrote:

Hi all,
I have an Advantest network analyser that uses a Teac FD-235GF 3156-U
floppy
drive. Teac cannot/willnot provide any information on the drive or a
suitable teac replacement. They tell me it's a proprietary drive and
to contact Advantest. Advantest won't help either, the analyser is
past service support life.

Anyone have a collection of NOS or even used FD-235GF 3156-U drives I
can buy ( want around 3-5)

Or - anyone have any info on the teac 235-gf apart from the teac.jp
website glossy and any knowledge of a suitable replacement?

If I can determine what the jumper settings mean perhaps I can find
another drive that would suit. Anyone have a copy of the service
manual for the drive that identifies the jumper settings?

The jumper configuration for the drive as installed in the 3762ah is
per the following list.
A1-B1,B4-C4,B3-C3,D4-E4, F1-G1
D1-D2, E2-E3, G3-G4

Any help appreciated

Thanks
Greg

That could just be a standard PC floppy drive. Teac FD-235's are/used to
be used in IBM compatible PC's. I'm sure I have some kicking around.
I'll have a look on Monday when I get into work.

--
Best Regards:
Baron.


Hi Baron,
the PC drives are FD-235 HF not GF as far as I've been able to identify
and
the jumper set is different.

For the most part I reckon all I need is to know the jumper matrix
settings,
from there I should be able to sort out modifying any current drive to
suit.

However, if you do find some GF drives I would be most interested.

Thanks for the help
Greg

***
Do any of these help?

http://www.teac.com/DSPD/pdf/3fd0105a.pdf

http://www.google.com.au/search?num=...G=Search&meta=

http://www.hkinventory.com/public/Of...=0&datecode =

Larry



Hi Larry,
thanks for the links - unfortunately not much use I'm afraid. I hadn't seen
that pdf on the teac site but as it was about HG to HF differences no
mention of the GF drive.

I'm particularly looking for the GF drive not the HF drive. The jumper pad
on this drive allows for all sorts of non standard pinout configurations
such as density select on pin 6 rather than 2 etc. The problem is some of
these interfaces have changed over time, for example the density select can
be either an input or an output or both depending on the drive and the
controller and without the jumper data I'm not sure how the drive is
actually configured to operate.

The controller on the drive is a T4A34F, again no luck in finding any info
on this chip to allow me to identify what pin goes to what jumper. If anyone
has a datasheet on that teac IC that would also be of some use.

Thanks
Greg

You might want to pose this question to the floppy hardware gurus at
"Individual Computers."

They make a product called the "Catweasel" which reads all floppy formats
known to man. as such, they proabably have some experience with drives.

http://siliconsonic.de/contact/contact_e.htm

Or Tim Mann is also a floppy guru.
http://www.tim-mann.org/catweasel.html

gcd wrote:


"Baron" wrote in message
...
gcd wrote:

Hi all,
I have an Advantest network analyser that uses a Teac FD-235GF
3156-U floppy
drive. Teac cannot/willnot provide any information on the drive or
a suitable teac replacement. They tell me it's a proprietary drive
and to contact Advantest. Advantest won't help either, the analyser
is past service support life.

Anyone have a collection of NOS or even used FD-235GF 3156-U drives
I can buy ( want around 3-5)

Or - anyone have any info on the teac 235-gf apart from the teac.jp
website glossy and any knowledge of a suitable replacement?

If I can determine what the jumper settings mean perhaps I can find
another drive that would suit. Anyone have a copy of the service
manual for the drive that identifies the jumper settings?

The jumper configuration for the drive as installed in the 3762ah is
per the following list.
A1-B1,B4-C4,B3-C3,D4-E4, F1-G1
D1-D2, E2-E3, G3-G4

Any help appreciated

Thanks
Greg

That could just be a standard PC floppy drive. Teac FD-235's are/used
to
be used in IBM compatible PC's. I'm sure I have some kicking around.
I'll have a look on Monday when I get into work.

--
Best Regards:
Baron.


Hi Baron,
the PC drives are FD-235 HF not GF as far as I've been able to
identify and the jumper set is different.

For the most part I reckon all I need is to know the jumper matrix
settings, from there I should be able to sort out modifying any
current drive to suit.

However, if you do find some GF drives I would be most interested.

Thanks for the help
Greg

I've made a note about that difference ! I have some weird HP kit
kicking about with 3.5" floppies in them ! Without looking I'm sure
that they are Teac drives. I'll find out tomorrow.

--
Best Regards:
Baron.

Baron wrote:

gcd wrote:


"Baron" wrote in message
...
gcd wrote:

Hi all,
I have an Advantest network analyser that uses a Teac FD-235GF
3156-U floppy
drive. Teac cannot/willnot provide any information on the drive or
a suitable teac replacement. They tell me it's a proprietary drive
and to contact Advantest. Advantest won't help either, the analyser
is past service support life.

Anyone have a collection of NOS or even used FD-235GF 3156-U drives
I can buy ( want around 3-5)

Or - anyone have any info on the teac 235-gf apart from the teac.jp
website glossy and any knowledge of a suitable replacement?

If I can determine what the jumper settings mean perhaps I can find
another drive that would suit. Anyone have a copy of the service
manual for the drive that identifies the jumper settings?

The jumper configuration for the drive as installed in the 3762ah
is per the following list.
A1-B1,B4-C4,B3-C3,D4-E4, F1-G1
D1-D2, E2-E3, G3-G4

Any help appreciated

Thanks
Greg

That could just be a standard PC floppy drive. Teac FD-235's
are/used to
be used in IBM compatible PC's. I'm sure I have some kicking
around. I'll have a look on Monday when I get into work.

--
Best Regards:
Baron.


Hi Baron,
the PC drives are FD-235 HF not GF as far as I've been able to
identify and the jumper set is different.

For the most part I reckon all I need is to know the jumper matrix
settings, from there I should be able to sort out modifying any
current drive to suit.

However, if you do find some GF drives I would be most interested.

Thanks for the help
Greg

I've made a note about that difference ! I have some weird HP kit
kicking about with 3.5" floppies in them ! Without looking I'm sure
that they are Teac drives. I'll find out tomorrow.


Hi Greg,
I've had a look through a number of bits of HP kit ! They are all Teac
FD-235-HF's I'm afraid.
I'm very sorry about that ! I felt sure that I could help. :-(

--
Best Regards:
Baron.

"Baron" wrote in message
...
Baron wrote:

gcd wrote:


"Baron" wrote in message
...
gcd wrote:

Hi all,
I have an Advantest network analyser that uses a Teac FD-235GF
3156-U floppy
drive. Teac cannot/willnot provide any information on the drive or
a suitable teac replacement. They tell me it's a proprietary drive
and to contact Advantest. Advantest won't help either, the analyser
is past service support life.

Anyone have a collection of NOS or even used FD-235GF 3156-U drives
I can buy ( want around 3-5)

Or - anyone have any info on the teac 235-gf apart from the teac.jp
website glossy and any knowledge of a suitable replacement?

If I can determine what the jumper settings mean perhaps I can find
another drive that would suit. Anyone have a copy of the service
manual for the drive that identifies the jumper settings?

The jumper configuration for the drive as installed in the 3762ah
is per the following list.
A1-B1,B4-C4,B3-C3,D4-E4, F1-G1
D1-D2, E2-E3, G3-G4

Any help appreciated

Thanks
Greg

That could just be a standard PC floppy drive. Teac FD-235's
are/used to
be used in IBM compatible PC's. I'm sure I have some kicking
around. I'll have a look on Monday when I get into work.

--
Best Regards:
Baron.


Hi Baron,
the PC drives are FD-235 HF not GF as far as I've been able to
identify and the jumper set is different.

For the most part I reckon all I need is to know the jumper matrix
settings, from there I should be able to sort out modifying any
current drive to suit.

However, if you do find some GF drives I would be most interested.

Thanks for the help
Greg

I've made a note about that difference ! I have some weird HP kit
kicking about with 3.5" floppies in them ! Without looking I'm sure
that they are Teac drives. I'll find out tomorrow.


Hi Greg,
I've had a look through a number of bits of HP kit ! They are all Teac
FD-235-HF's I'm afraid.
I'm very sorry about that ! I felt sure that I could help. :-(

--
Best Regards:
Baron.

Hi Baron,
no problems. Thanks for looking though.
I've had some success using a standard pc drive. Had to use DS0 rather than
DS1 (expected) and needed to ensure the drive was using disk change on pin
34. The only thing that is still a little peculiar is the density select and
whether it's an input/output or both. Using a standard PC drive I need to
use a HD disk but cover over the HD hole and that seems to work reliably. On
the original drive I would use HD without covering up the hole. The only
issues I end up with is that the drive light is always 1/2 on when not in
use.

I'll keep looking for FD-235GF data and playing around. i'ts almost sorted
now

Thanks
Greg

On Tue, 24 Feb 2009 17:43:49 +1100, "gcd"
put finger to keyboard
and composed:

I've had some success using a standard pc drive. Had to use DS0 rather than
DS1 (expected) and needed to ensure the drive was using disk change on pin
34. The only thing that is still a little peculiar is the density select and
whether it's an input/output or both. Using a standard PC drive I need to
use a HD disk but cover over the HD hole and that seems to work reliably. On
the original drive I would use HD without covering up the hole. The only
issues I end up with is that the drive light is always 1/2 on when not in
use.

I'll keep looking for FD-235GF data and playing around. i'ts almost sorted
now

Thanks
Greg

This URL suggests that pin 2 is an input to the drive:
http://pinouts.ru/Storage/InternalDisk_pinout.shtml

I suggest you look at the datasheet for an old multi-IO chip such as
were used on 486 and Pentium motherboards, before the functions were
incorporated into the chipset.

For example, here is the datasheet for a Winbond W83757F:
http://www.datasheetarchive.com/data...SA00379504.pdf

Amongst the FDC pins is RWC, Reduced Write Current. "This signal can
be used on two-speed disk drives to select the transfer rate."

Logic 0 = 250 Kb/s
Logic 1 = 500 Kb/s

It is described as an "open-drain output pin with 24 mA sink
capability".

I've seen this pin used in 2-speed 5.25" drives, but not in 3.5"
drives. It could be that the HD hole in the diskette tells the [PC]
drive what write current to use, but the drive does not report the
diskette type to the controller.

Does your Advantest network analyser write 1.44MB or 720KB of data to
the diskettes? It would seem odd if the drive were writing to the
diskette as if it were a 720KB lo-den type while the controller were
transferring data at a hi-den (500 Kb/s) rate.

Could it be that your current setup is operating at a 250Kb/s data
rate, and that your diskette's capacity is being reduced to 720KB?
Could it be that the original FDD uses the "RWC" pin as an output
rather than an input, and that it communicates the diskette type to
the analyser, in which case the analyser could automatically adjust
the data rate to suit??? In the latter case, if the analyser doesn't
get any feedback from the drive, perhaps it defaults to a lo-den data
rate. You might like to experiment with a pull-down or pullup resistor
on this pin.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On Sun, 22 Feb 2009 14:23:57 +1100, "gcd"
put finger to keyboard
and composed:

such as density select on pin 6 rather than 2 etc. The problem is some of
these interfaces have changed over time, for example the density select can
be either an input or an output or both depending on the drive and the
controller and without the jumper data I'm not sure how the drive is
actually configured to operate.

FWIW, this document refers to FD55-GFR 5.25" drives:
http://www.teac.com/DSPD/pdf/5fd0050a.pdf

There is an LG strap and an I strap that define how the drive behaves
in lo-den and hi-den modes.

The controller on the drive is a T4A34F, again no luck in finding any info
on this chip to allow me to identify what pin goes to what jumper. If anyone
has a datasheet on that teac IC that would also be of some use.

Thanks
Greg

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On Wed, 25 Feb 2009 08:48:06 +1100, Franc Zabkar
put finger to keyboard and composed:

On Sun, 22 Feb 2009 14:23:57 +1100, "gcd"
put finger to keyboard
and composed:

such as density select on pin 6 rather than 2 etc. The problem is some of
these interfaces have changed over time, for example the density select can
be either an input or an output or both depending on the drive and the
controller and without the jumper data I'm not sure how the drive is
actually configured to operate.

FWIW, this document refers to FD55-GFR 5.25" drives:
http://www.teac.com/DSPD/pdf/5fd0050a.pdf

There is an LG strap and an I strap that define how the drive behaves
in lo-den and hi-den modes.

There is also an In-Use (IU) jumper set that defines the conditions
under which the in-use LED turns on. The standard jumpering for a PC
AT system is to illuminate the LED whenever Drive Select is active,
whether or not the drive is actually doing anything. Is it possible
that the controller is constantly checking the DiskChange pin and
thereby activating the LED?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

"Franc Zabkar" wrote in message
...
On Wed, 25 Feb 2009 08:48:06 +1100, Franc Zabkar
put finger to keyboard and composed:

On Sun, 22 Feb 2009 14:23:57 +1100, "gcd"
put finger to keyboard
and composed:

such as density select on pin 6 rather than 2 etc. The problem is some of
these interfaces have changed over time, for example the density select
can
be either an input or an output or both depending on the drive and the
controller and without the jumper data I'm not sure how the drive is
actually configured to operate.

FWIW, this document refers to FD55-GFR 5.25" drives:
http://www.teac.com/DSPD/pdf/5fd0050a.pdf

There is an LG strap and an I strap that define how the drive behaves
in lo-den and hi-den modes.

There is also an In-Use (IU) jumper set that defines the conditions
under which the in-use LED turns on. The standard jumpering for a PC
AT system is to illuminate the LED whenever Drive Select is active,
whether or not the drive is actually doing anything. Is it possible
that the controller is constantly checking the DiskChange pin and
thereby activating the LED?

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Hi again Franc,
I've been across all the jumpers on the drive I'm playing with and none
appear to affect the dim led. it goes off but I'll keep playing around if I
can't find the info I'm after

Cheers
Greg

"Franc Zabkar" wrote in message
...
On Tue, 24 Feb 2009 17:43:49 +1100, "gcd"
put finger to keyboard
and composed:

I've had some success using a standard pc drive. Had to use DS0 rather
than
DS1 (expected) and needed to ensure the drive was using disk change on
pin
34. The only thing that is still a little peculiar is the density select
and
whether it's an input/output or both. Using a standard PC drive I need to
use a HD disk but cover over the HD hole and that seems to work reliably.
On
the original drive I would use HD without covering up the hole. The only
issues I end up with is that the drive light is always 1/2 on when not in
use.

I'll keep looking for FD-235GF data and playing around. i'ts almost sorted
now

Thanks
Greg

This URL suggests that pin 2 is an input to the drive:
http://pinouts.ru/Storage/InternalDisk_pinout.shtml

I suggest you look at the datasheet for an old multi-IO chip such as
were used on 486 and Pentium motherboards, before the functions were
incorporated into the chipset.

For example, here is the datasheet for a Winbond W83757F:
http://www.datasheetarchive.com/data...SA00379504.pdf

Amongst the FDC pins is RWC, Reduced Write Current. "This signal can
be used on two-speed disk drives to select the transfer rate."

Logic 0 = 250 Kb/s
Logic 1 = 500 Kb/s

It is described as an "open-drain output pin with 24 mA sink
capability".

I've seen this pin used in 2-speed 5.25" drives, but not in 3.5"
drives. It could be that the HD hole in the diskette tells the [PC]
drive what write current to use, but the drive does not report the
diskette type to the controller.

Does your Advantest network analyser write 1.44MB or 720KB of data to
the diskettes? It would seem odd if the drive were writing to the
diskette as if it were a 720KB lo-den type while the controller were
transferring data at a hi-den (500 Kb/s) rate.

Could it be that your current setup is operating at a 250Kb/s data
rate, and that your diskette's capacity is being reduced to 720KB?
Could it be that the original FDD uses the "RWC" pin as an output
rather than an input, and that it communicates the diskette type to
the analyser, in which case the analyser could automatically adjust
the data rate to suit??? In the latter case, if the analyser doesn't
get any feedback from the drive, perhaps it defaults to a lo-den data
rate. You might like to experiment with a pull-down or pullup resistor
on this pin.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.


Hi Franc,
yes - pin 2 determines the density of the drive which is usally related to
the speed of the drive. Some fdc chips expect this to be sent to the dhip
from the drive, some expect to send it out to the drive and others are
bi-directional. Just depends on the age of the drive and the controller, as
things changed from shugart to pc format interface.

This is why I'd like to get the jumper info - it would tell all.

I've had a bit of play with pull ups with no luck but I'll persist

Thanks for the links and suggestions, mind you, if all I end up with is a
light 1/2 on I can live with that - just need to ensure the configuration i
end up with is reliable in terms of data storage


Greg

gcd Inscribed thus:
"Franc Zabkar" wrote in message
...
On Tue, 24 Feb 2009 17:43:49 +1100, "gcd"
put finger to
keyboard and composed:

I've had some success using a standard pc drive. Had to use DS0
rather than DS1 (expected) and needed to ensure the drive was using
disk change on pin 34.

DS1 (Drive Select) was the result of some bright spark realising that a
twist in the cable could be used to determine which drive was "A" In
practice it probably saved a lot of money for the manufacturers and
confused techies !

The only thing that is still a little peculiar is the density
select and whether it's an input/output or both.

It sticks in my mind that it was always an output in the sense that it
was used to detect the difference between 720/144 Mb disks and set the
rotational speed, 300/360 rpm I belive.

Using a standard PC drive I need to use a HD disk but cover over the
HD hole and that seems to work reliably. On the original drive I
would use HD without covering up the hole.

I wonder if that is anything to do with difference in the material used
for the magnetic coating.

The only issues I end up with is that the drive light is always 1/2
on when not in use.

I'll keep looking for FD-235GF data and playing around. i'ts almost
sorted now

Thanks
Greg

--
Best Reagrds:
Baron.

On Wed, 25 Feb 2009 12:09:23 +0000, Baron
put finger to keyboard and
composed:

gcd Inscribed thus:

The only thing that is still a little peculiar is the density
select and whether it's an input/output or both.

It sticks in my mind that it was always an output in the sense that it
was used to detect the difference between 720/144 Mb disks and set the
rotational speed, 300/360 rpm I belive.

The IBM PC AT BIOS source listing indicates that IBM used data rates
of 500Kbps, 300Kbps, 250Kbps, and "reserved". In future designs, the
latter became 1Mbps and was assigned to 2.88MB FDDs.

The 3.5" 720KB and 1.44MB diskettes are both spun at 300 RPM, the
difference being that the latter has twice as many sectors per track
(18 vs 9). This results in data rates of 250Kb/s and 500Kb/s. Dual
speed 5.25" drives could spin at either 300RPM or 360RPM depending on
the density. A 1.2MB drive with 15 sectors/track would spin at 360RPM,
whereas a 360KB drive with 9 sectors/track would spin at 300RPM.
Although dual speed 1.2MB drives existed (I have two), IBM accounted
for the case where a 360KB DD 300RPM (250Kbps) diskette is used in a
HD fixed speed 360RPM drive by configuring the controller's digital
data separator with a matching 300Kbps data rate. AFAIK the dual speed
facility was never used on the PC platform. Instead pin 2 was used to
signal reduced write current.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:

On Wed, 25 Feb 2009 12:09:23 +0000, Baron
put finger to keyboard and
composed:

gcd Inscribed thus:

The only thing that is still a little peculiar is the density
select and whether it's an input/output or both.

It sticks in my mind that it was always an output in the sense that it
was used to detect the difference between 720/144 Mb disks and set the
rotational speed, 300/360 rpm I belive.

The IBM PC AT BIOS source listing indicates that IBM used data rates
of 500Kbps, 300Kbps, 250Kbps, and "reserved". In future designs, the
latter became 1Mbps and was assigned to 2.88MB FDDs.

The 3.5" 720KB and 1.44MB diskettes are both spun at 300 RPM, the
difference being that the latter has twice as many sectors per track
(18 vs 9). This results in data rates of 250Kb/s and 500Kb/s. Dual
speed 5.25" drives could spin at either 300RPM or 360RPM depending on
the density. A 1.2MB drive with 15 sectors/track would spin at 360RPM,
whereas a 360KB drive with 9 sectors/track would spin at 300RPM.
Although dual speed 1.2MB drives existed (I have two), IBM accounted
for the case where a 360KB DD 300RPM (250Kbps) diskette is used in a
HD fixed speed 360RPM drive by configuring the controller's digital
data separator with a matching 300Kbps data rate. AFAIK the dual speed
facility was never used on the PC platform. Instead pin 2 was used to
signal reduced write current.

- Franc Zabkar

Thanks for the refresh ! I see that I've confused the 5.25" & 3.5"
drives. Its a long time since I played around with the old stuff.
My original IBM AT is still under the bench collecting dust and heavens
knows what livestock is living in it. I've still got the full hight
360K drive as well.

--
Best Regards:
Baron.

On Wed, 25 Feb 2009 21:36:30 +0000, Baron
put finger to keyboard and
composed:

My original IBM AT is still under the bench collecting dust and heavens
knows what livestock is living in it. I've still got the full hight
360K drive as well.

I have many of the schematics for the original IBM PC/AT, including
the 360KB FDD.

Here is the FDD/HDD controller:
http://www.users.on.net/~fzabkar/PC-AT/FDC_HDC/

This sheet shows the floppy interface:
http://www.users.on.net/~fzabkar/PC-...C_HDC_Sht4.JPG

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar Inscribed thus:

On Wed, 25 Feb 2009 21:36:30 +0000, Baron
put finger to keyboard and
composed:

My original IBM AT is still under the bench collecting dust and
heavens
knows what livestock is living in it. I've still got the full hight
360K drive as well.

I have many of the schematics for the original IBM PC/AT, including
the 360KB FDD.

Here is the FDD/HDD controller:
http://www.users.on.net/~fzabkar/PC-AT/FDC_HDC/

This sheet shows the floppy interface:
http://www.users.on.net/~fzabkar/PC-...C_HDC_Sht4.JPG

- Franc Zabkar

Nice ! Are you Ok with me bookmarking that url ?

--
Best Reagrds:
Baron.

On Thu, 26 Feb 2009 11:46:24 +0000, Baron
put finger to keyboard and
composed:

Franc Zabkar Inscribed thus:

On Wed, 25 Feb 2009 21:36:30 +0000, Baron
put finger to keyboard and
composed:

My original IBM AT is still under the bench collecting dust and
heavens
knows what livestock is living in it. I've still got the full hight
360K drive as well.

I have many of the schematics for the original IBM PC/AT, including
the 360KB FDD.

Here is the FDD/HDD controller:
http://www.users.on.net/~fzabkar/PC-AT/FDC_HDC/

This sheet shows the floppy interface:
http://www.users.on.net/~fzabkar/PC-...C_HDC_Sht4.JPG

- Franc Zabkar

Nice ! Are you Ok with me bookmarking that url ?

All my stuff is public. I just hope IBM is OK with it.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Franc Zabkar wrote:

On Thu, 26 Feb 2009 11:46:24 +0000, Baron
put finger to keyboard and
composed:

Franc Zabkar Inscribed thus:

On Wed, 25 Feb 2009 21:36:30 +0000, Baron
put finger to keyboard and
composed:

My original IBM AT is still under the bench collecting dust and
heavens
knows what livestock is living in it. I've still got the full hight
360K drive as well.

I have many of the schematics for the original IBM PC/AT, including
the 360KB FDD.

Here is the FDD/HDD controller:
http://www.users.on.net/~fzabkar/PC-AT/FDC_HDC/

This sheet shows the floppy interface:
http://www.users.on.net/~fzabkar/PC-...C_HDC_Sht4.JPG

- Franc Zabkar

Nice ! Are you Ok with me bookmarking that url ?

All my stuff is public. I just hope IBM is OK with it.

- Franc Zabkar

Thanks.

--
Best Regards:
Baron.