15 Dec
2005
15 Dec
'05
4:42 a.m.
Subject: RE: Early 3.5" Floppy Drives
From: Chris M <chrism3667 at yahoo.com>
Date: Wed, 14 Dec 2005 16:02:06 -0800 (PST)
To: "General Discussion: On-Topic Posts Only" <cctech at
classiccmp.org>
any clue who actually made 8" controllers for PC's?
One of my APC's has a controller board and external
5.25" drives made by Butler Flats Associates. Not sure
what capacity the 8" drives have (haven't played with
them much yet), but I believe the resident controller
used a 765 chip. The Butler Flats boards used some
Western Digital chip. Funny.
--- Barry Watzman <Watzman at neo.rr.com> wrote:
> ...And there were 8" controllers for
> early PCs.
Any PC controller that can do 720k 3.5" format can do
8" as it's the same data rate. it's not what chips was
used it's how it was used.
Allison
15 Dec
15 Dec
9:32 a.m.
On 12/15/2005 at 7:42 AM Allison wrote:
Any PC controller that can do 720k 3.5" format can
do
8" as it's the same data rate. it's not what chips was
used it's how it was used.
Whoa. Sorry, I couldn't let this one go by unanswered.
8" drives use a 500K data clock rate, not 250K like the DS2D 720K 3.5". A
controller that supports 1.44M DSHD 3.5" should do just fine on 8". While
there were early 8" drives that used a lower clock rate, they were pretty
much gone by the time of the dawn of the PC. FM support with a modern
controller is a somewhat different kettle of fish. The nearest AT medium
to the 8" drive would be the 5.25" high-density diskette, which also spins
at the same rate--360 RPM.
That was the beauty of the NEC APC line--from 8" right down to 3.5", the
data format didn't vary one iota. The NEC 9801 floppies still record 1.3MB
on a 3.5" drive spinning at 360 RPM.
But the PC-XT 8" drive controllers were a special beast, honest.
Cheers,
Chuck
1:43 p.m.
On Thu, 15 Dec 2005, Allison wrote:
Any PC controller that can do 720k 3.5" format
can do
8" as it's the same data rate. it's not what chips was
used it's how it was used.
It's rare enough that Allison (or Tony) make a mistake,
that it is a rare opportunity to be able to disagree with
any confidence.
Any PC controller that can do "standard" 360K, can do 720K 3.5".
Only difference is whether the OS and/or BIOS are happy with the
trivial differences.
But unless we allow some "re-programming with solder and dead bugs",
many of the 8 bit FDC boards are hardwired to MFM, yet have the data
transfer rate that the 8" would want for FM.
The original IBM FDC board for the 5150 could be modified for 8"
(Flagstaff Engineering did so), but it's a lot of extra wires.
On the other hand, most FDC boards that support 1.2M
can do 8" DD.
The ones that also support FM can usually handle 8" SD.
'course there are SOME that are designed so weird that
they still can't.
Boards for 5150 that support 8" include the popular Compaticard,
Flagstaff Engineering, Maynard, Vista, J-Disk, MMF, etc.
--
Grumpy Ol' Fred cisin at xenosoft.com
4:49 p.m.
Any PC controller that can do 720k 3.5" format
can do
8" as it's the same data rate. it's not what chips was
I don;'t think you mean that!. The 720K 3.5" format is the same data rate
as the 360K 5.25" format. You mean any controller that can do the 1.44M
3.5" format (or for that matter the 1.2M 5.25" format), surely. Those are
the same as the 8" data rate.
used it's how it was used.
-tony
5:43 p.m.
On 12/16/2005 at 12:49 AM ard at p850ug1.demon.co.uk wrote:
Yeah, he did--sort of. This assumes that the data separator can be
jiggered to deliver separated FM data at the same rate that it delivers
3.5" separated MFM data. i.e., 8" FM has the same data rate as 720K 3.5"
MFM.
Although, I'm still puzzling over my databook's definition of pin 21, it
says "500 KHz for FM and 1 MHz for MFM" but makes no mention of write data
rate (i.e. mimifloppy vs. 8"). Could this be simply something left out?
Cheers,
Chuck
Any PC
controller that can do 720k 3.5" format can do
8" as it's the same data rate. it's not what chips was
I don;'t think you mean that!. The 720K 3.5" format is the same data rate
as the 360K 5.25" format. You mean any controller that can do the 1.44M
3.5" format (or for that matter the 1.2M 5.25" format), surely. Those are
the same as the 8" data rate.
6898
days inactive
6899
days old
4 comments
4 participants
participants (4)
-
ajp166＠bellatlantic.net -
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
cisin＠xenosoft.com