>Subject: RE: Early 3.5" Floppy Drives
> From: "Chuck Guzis" <cclist at sydex.com>
> Date: Thu, 15 Dec 2005 09:32:54 -0800
> To: cctalk at classiccmp.org
>
>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.
;) your assumption is double density. 8" SSSD is not that fast.
I never said formats were the same or even dive interface only that
the data rates fly.
765A write clock rate by drive and density, bit rate is clock/2.
Size density format writeclock
-----------------------------------
8" DD MFM 1000khz
8" SD FM 500khz (8"SSSD 241k CP/M standard)
5.25 DD MFM 500khz (40track is 360k, 80track 720k)
5.25 SD FM 250khz
3.5" HD MFM 1000khz (1.44mb) (looks like 8" different CHS)
3.5" DD MFM 500khz (720k) (same rate as 5.25 DD and 8" SD)
3.5" ?? FM 250khz (not used obsolete)
None of this has anything to do with rotation rate of the media.
Actual data storage capability is format dependent.
One example that was known the to CP/M world was 5.25" 80track (FD55F)
two sided at either 720k or ~780k I was sometimes called QD as it
was really the same as the 360k but twice the tracks (48 tpi vs 96).
So happens that the 3.5" drive can be plugged in and used exactly
as if it were a FD55F for the same 720k as I do it all the time
>from a CP/M system to DOS and the CPM80 side has a utility that
read/writes DOS FAT files. I'd have used 1.44 but the WD1770 literally
cannot run at the required rate (not rated to either!).
I'll let you all in on a dirty trick. The 765(A) outputs a signal on
pin26 called FM, that is used to select data rates /2 ALWAYS. If you lift
the pin the data rates for FM mode are now twice as fast and suitable
for many other uses like 8" media. For the integrated flavors of 765
the same effect can be had by twiddling bits in the drive control register.
If all else fails, you can double the the 8 or 16 mhz clock source
used to 16/32 as needed. I have taked the 9.6mhz out and used higher
on one board 16mhz so that switching to AT 5.25HD got me 8"DD instead
without futzing with drivespeed (rotation rate) that means nothing to
most 3.5, 5.25 (including FD55GFR with the jumper pulled) and 8" drive.
>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.
Not really. I can take the stock IBM XT long board and with one change
make it do DSDD 8" (other than cable adaptor). Common parts cost 'bout
$1, acutally cheaper now than 20 years ago then it would have been 1.89.
Replace the 8mhz clock source with 16mhz.
Thats how it's done.
Allison
>
>Subject: Re: Good haul of old pc stuph
> From: "Curt @ Atari Museum" <curt at atarimuseum.com>
> Date: Thu, 15 Dec 2005 09:37:30 -0500
> To: General at smtp1.suscom.net, "Discussion at smtp1.suscom.net":On-Topic and
> Off-Topic Posts <cctalk at classiccmp.org>
>
>Hmmmm XT based IDE controllers??? Interesting, I only recall using
>the stock MFM's and using SCSI when larger space was needed.
>
>What is the manufacturer name on the adapters?
Cut from the posting you enclosed..
>>>The one I still have is made by Acculogic, called the
>>>sIDE/16 or something.
Mine also says that. I also had a PS2/30 which was an XT
in reality and could install a connor 420mb IDE.
All it took was a 8bit/16bit trnaslation usinga pair of latches
and some buffers. the only part of IDE thats actually 16bits
wide is data transfers, the registers are bytes. The MFM
controllers of the time had the same register layout. The
WD1003 was likely the best known ISA16 (WD1002 was the ISA8
version) controller for MFM and it's just like talking to
an IDE drive.
To prove the point once I took a spare WD1003 jammed a few address
bits and wired a IDE male connecotr to the needed pins and hooked
the controller, and a 31mb drive to the IDE port of a 486board
and then set the CHS in the bios and tada, it works. It's
possible as that board was the prototype for the IDE drives
on board logic and in itself was a standard.
Since then IDE (ATAPI) has evolved some and there are a few
twists added.
Allison
>
>
>Curt
>
>
>
>Allison wrote:
>
>>>Subject: re: Good haul of old pc stuph
>>> From: Chris M <chrism3667 at yahoo.com>
>>> Date: Mon, 12 Dec 2005 17:50:26 -0800 (PST)
>>> To: talk <cctalk at classiccmp.org>
>>>
>>>There were a few XT IDE controllers back in the day.
>>>The one I still have is made by Acculogic, called the
>>>sIDE/16 or something. People who have used them claim
>>>they work well. Either this one was blown to begin
>>>with or the drive was at fault. It's mostly discrete
>>>logic, the exception being a GAL or PAL as I recall.
>>>There wasn't any firmware on it from what I remember.
>>>What did I do with the thing?
>>>
>>>
>>
>>XT IDE adaptors are not uncommon and fairly simple devices.
>>I have one or two of them and could make one. They do work
>>well enough. The that drives usually connected to them
>>have usually died by age.
>>
>>Allison
>>
>>
>>
>>
>>
>
>
>--
>No virus found in this outgoing message.
>Checked by AVG Free Edition.
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>
>Subject: RE: Early 3.5" Floppy Drives
> From: Fred Cisin <cisin at xenosoft.com>
> Date: Thu, 15 Dec 2005 13:43:43 -0800 (PST)
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>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.
The software interface is a seperate issue. Very few media smaller
than 8" used 26 sectors per track FM or MFM.
>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.
The IDE8 FDC were not hard wired for MFM. Amen. The selection
of FM/MFM is a bit in the command byte. It's bit 6. Write data
Fm is 05h and write data MFM is 45h. Now what the logic connected
to pin26 does with the signal is possibly unknown but the resulting
output to the drive always follows the command byte.
>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.
Yes there are a few that pin26 goes nowhere and the resulting FM
data rate is then twice what you would expect. For some cases
that is an advantage. ;)
Allison
Speaking of Geoworks, anyone have a copy of the rare 8088 devkit for GEOS?
IMHO, it's lack of wide distribution of a devkit that killed GEOS the
deadest. That and flying toasters.... I probably would have used it for my
main desktop if I could have coded for it....
I'm also looking for a copy of the devkit for Windows 1.0X. Being able to
code for Windows 1 would kick a**.
Eric
On 12/12/05, Jim Leonard <trixter at oldskool.org> wrote:
>
> Allison wrote:
>
> If you used Geoworks, or
> Ghostscript (I used a retail package called "GOSCRIPT"), or Win 3.1, you
> could
> use any font you want and the print subsystem would just rasterize it as
> graphics.
> --
> Jim Leonard (trixter at oldskool.org)
> http://www.oldskool.org/
> Want to help an ambitious games project?
> http://www.mobygames.com/
> Or check out some trippy MindCandy at
> http://www.mindcandydvd.com/
>
>
>Subject: RE: Early 3.5" Floppy Drives
> From: "Chuck Guzis" <cclist at sydex.com>
> Date: Thu, 15 Dec 2005 11:30:29 -0800
> To: cctalk at classiccmp.org
>
>On 12/15/2005 at 1:18 PM Allison wrote:
>
>>;) your assumption is double density. 8" SSSD is not that fast.
>>I never said formats were the same or even dive interface only that
>>the data rates fly.
>
>Nope. I'm just going by the 765 data sheet:
>
>"Pin 19 - CLK - Single-phase 8 MHz (or 4 MHz for mini-floppies) squarewave
>clock"
>
>IOW, if you supported 3.5 DD (or SD) floppies, you weren't going to be
>able to do an A1 8" floppy without changing the clock.
;) You know not the part you speak of. Question, what it that clock used
for? Hint data rates are NOT tied to it.
The internal timers (HLT, HST, SR) are. So if you need real fast or real
slow step rates the chip clock is important.
You have to read the apnotes and there was a users manaual at one time.
there are many things that if you apply WD177x or 179x rules to will not
make sense. Such as the use of TC.
>Same thing obtains for the WD 179x - "Pin 24 - CLOCK - This input requires
>a free-running 50% duty cycle square wave clock for internal timing
>reference. 2 MHz +/- 1% for 8" drives, 1 MHz +/- 1% for mini-floppies."
Not even close 765 is a wholly differnt animal. The Read operation needs
RDW and the write must have WC. Both are independent of the chipclock.
(note: the 37C65 and later parts integrate a lot of logic that was
external to 765 but logically still are. so their behavour is rule driven.)
>The 279x has a clock divider that's programmed by pin 17 (5/8).
Again differnt animal and based on 179x.
>Look at the grandaddy of the 8" XT drive controllers, the CompatiCard I.
>It uses port 7F2H to change the 765 clock from 4 to 8 MHz for 8" support.
>MFM/FM doesn't enter into the equation--that's programmed into the read and
>write commands and the data separator.
Nope.
>But an old XT-era 720K 3.5"/5.25" controller couldn't do this
>clock-switching trick unless it could also support 1.2/1.44 media.
Nope not needed.
The serial logic of the 765 is decoupled from the control and status
logic. If you used 4mhz for chipclock and did 8" your fastest step rate
would be half as fast as if you used 8mhz. Same you be true for Head load
time and head unload time. Also when he chip is idle (not seen on PC hardware)
it scans all four drives for "Ready and Disk Change", the scan rate for that
would also be off by /2.
Allison
GEM was in fact developed by DR (Digita Research) and when DR got
bought by Caldera, it became free software. Not "open source for
non-commercial use" like CP/M or DR-DOS, but actual GPL software.
Consequently, it has been developed into just about the best GUI you
can throw onto a 286 and have work. See the latest version of the
leading distro here: http://gem.shaneland.co.uk/opengem5core.html
>
>Subject: Re: Scanned Data Separator Appnotes
> From: woodelf <bfranchuk at jetnet.ab.ca>
> Date: Thu, 15 Dec 2005 12:55:39 -0700
> To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>
>Roger Merchberger wrote:
>
>> Allison sent me the scans of the appnotes for the data separator /
>> floppy interface circuits, and I have put them on the web for anyone
>> who wants access to them.
>>
>> http://www.30below.com/~zmerch/classics/datasep/
>>
>Well I think one may have metastable problem with theTTL data seperators.
>You want a second flip/flop to buffer the edge detect flip/flop After
>that the
>dog's hair color will stay black unless you have a poodle, and all will
>be fine.
It was test and works well enough to find it self used on many PCs.
Was it the best, no, only ok. Though it was 100x better than the 1771
internal data sep.
Allison
Allison sent me the scans of the appnotes for the data separator / floppy
interface circuits, and I have put them on the web for anyone who wants
access to them.
http://www.30below.com/~zmerch/classics/datasep/
4 files, monochrome JPG, enter at your own risk, and I'm not to be held
responsible if your dog's hair turns blue because of it. ;-)
Laterz,
Roger "Merch" Merchberger
--
Roger "Merch" Merchberger -- SysAdmin, Iceberg Computers
_??_ zmerch at 30below.com
(?||?) If at first you don't succeed, nuclear warhead
_)(_ disarmament should *not* be your first career choice.
>
>Subject: RE: Early 3.5" Floppy Drives
> From: Roger Merchberger <zmerch at 30below.com>
> Date: Thu, 15 Dec 2005 13:40:44 -0500
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>Rumor has it that Allison may have mentioned these words:
>[snippety]
>
>>Size density format writeclock
>>-----------------------------------
>>8" DD MFM 1000khz
>>8" SD FM 500khz (8"SSSD 241k CP/M standard)
>>
>>5.25 DD MFM 500khz (40track is 360k, 80track 720k)
>>5.25 SD FM 250khz
>>
>>3.5" HD MFM 1000khz (1.44mb) (looks like 8" different CHS)
>>3.5" DD MFM 500khz (720k) (same rate as 5.25 DD and 8" SD)
>>3.5" ?? FM 250khz (not used obsolete)
>
>3.5" FM was used for microcomputers - the Tandy Portable Disk Drive (OEMmed
>by Brother, IIRC) was 40 tracks, 2SPT FM w/100K storage. Serial port
>driven, and worked with the Tandy Model 100/102/200 laptops. In my Service
>manual for the critter, it did mention the density, but I don't have that
>handy. DD disks worked just fine on it (read: data life at least into the
>10 year range), but HD didn't work so well, IIRC.
>
>The TPDD2 was also FM, but used an 80 track drive (set into 2 banks for
>compatibility with the TPDD1) for 200K storage.
>
>Laterz,
>Roger "Merch" Merchberger
;) it's obsolete. I know there were at least 20 formats not mentioned
that were "out of the mainstream" so more exceptions are known.
However looking at the clock rates mentioned I'd guess it can be done. ;)
Allison
