PC/XT clone - SFRM72-TU100K or SFR1M44-U100(K) ?

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PC/XT clone - SFRM72-TU100K or SFR1M44-U100(K) ?

Postby Jo22 » 2018-1-06 @ 07:23

Hi everyone,

I've got a little question to you users of that GOTEK floppy emulator :


Since my PC/XT clone has a troublesome 3.5" 720KB drive, which emulator do you recommend as a replacement (if any) ?

And does that SFR1M44 model also work in 720KB or 360KB "mode", just like a real 3.5" 1.44MB drive would do ?


Any suggestions welcome.

-
I'm currently using real floppies and I'm happy with them so far. :)
If 720KB drives and disks weren't so rare nowerdays, I wouldn't think of changing that now.
(One of my 286es also has a 720KB drive, but works fine and rarely needs any cleaning).
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Re: PC/XT clone - SFRM72-TU100K or SFR1M44-U100(K) ?

Postby konc » 2018-1-06 @ 08:52

If you're interested in continuing using a real floppy drive, try replacing your drive with a 1.44MB one. Yes, just a simple swap. The result might surprise you ;)
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Re: PC/XT clone - SFRM72-TU100K or SFR1M44-U100(K) ?

Postby Errius » 2018-1-06 @ 10:00

The disks are easy to get. Just go on eBay and look for Amiga users dumping their old ones.
konc wrote:If you're interested in continuing using a real floppy drive, try replacing your drive with a 1.44MB one. Yes, just a simple swap. The result might surprise you ;)

Are there issues sharing 3.5" DD disks between DD and HD drives, as there are with 5.25" DD disks? (5.25" DD disks written in HD drives cannot be read reliably in DD drives.)
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Re: PC/XT clone - SFRM72-TU100K or SFR1M44-U100(K) ?

Postby Jo22 » 2018-1-06 @ 13:38

Thank you very much for the replies, guys! :)

I'm a bit torn between doing a replacement and keeping the machine in an authentic state.
(On the other hand : What use has authencity, if the machine is in an unusable state ? I'm no owner of a museum. ;) )

The idea of using used Amiga floppies is tempting, though I'm a bit scared also,
since I haven't had the best experience with used disk in the past so far and
don't want to ruin my drives (cleaning itself is no problem, but constantly disassembling drives is annoying.
And as clumsy as I am sometimes, I'll sure end up damaging these oldies somewhen in that process).

-
Speaking of diskette drives, file transfer with the PC/XT is a bit complicated at the moment. :sweatdrop:
The 720KB drive is the only way to transfer data with other machines.
I'm using a 286 with another 720KB drive for that purpose at the moment.

Using a 1.44MB drive and a 1.44MB disk (in 720KB) on a modern PC also works for me,
but only for a brief moment: Doing that "tape the hole" method is less reliable here,
since I get "setor not found" errors and "read errors" on the PC/XT quite quickly.
(During approximately a few days, the floppies become steadily more difficult to read.)

The 720KB drive in the 286 however, is more forgiving, but it won't format 1.44MB disks in 720KB.
Interestingly, down-formatting 1.44MB disks works fine with an older USB floppy on a Win7 PC.
Using format a: /f:720 on the command line works. But even here, I still get read errors from time to time
when using these re-formatted HD disks in the 286's 720KB drive.
On other 1.44MB drives or in the USB drive it was formatted with,
I usually get no errors.
-

Alternatively, I also thought about using a LapLink or null-modem cable for file transfer..
While the machine has both a Centronics parallel port and a serial port, they are useless for now.
The Centronics port is a real Centronics port (no DB25) and the serial port has an inverted 25pin
connector which I can find no pinout for.


As for the GOTEK, I've found a blog post in concjuction with an Atari ST.
Apparently, the floppy controller of the Atari has to run at a higher speed to be compatible with the SFR1M44 model.

Does anybody know if this issue also happens when connecting it to the XT's PC floppy controller ?
As far as I remember, the high-speed floppy controllers were introduced with the PC/AT architecture
and weren't available to PC/XT machines without retro-fitting them with new floppy controller cards.

http://www.tonmann.com/2014/08/gotek-floppy-emulator-sfr1m44-u100-at-inside-the-atari-st/
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Re: PC/XT clone - SFRM72-TU100K or SFR1M44-U100(K) ?

Postby konc » 2018-1-06 @ 16:10

I believe you're over-complicating things unnecessarily. Connecting a 1.44MB drive to the XT and writing HD disks on the 1.44MB drive of a modern computer won't give you any problems (at least no more than having to deal with the ridiculous reliability of recently produced floppy disks). Now you're switching between HD and DD drives.
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Re: PC/XT clone - SFRM72-TU100K or SFR1M44-U100(K) ?

Postby Jo22 » 2018-1-06 @ 20:14

I guess you're right, haha. I'm complicating things because of psychological aspects, too. :sweatdrop:
Point is, that computer is older than me and I have too much respect for it to planlessely fiddle around with it.
For example, it still has got the original 20MB hard disk from '85 installed.
Even though the drive is quite small for my use, I still can't bring myself to do an upgrade.
Knowing myself, I'd rather install a disk compression card or just use DoubleDisk (silly, I know).
Heck, even installing DOS 6.2 wasn't easy. I still feel like I should have used DOS 3.3 instead.
But my sanity told me to use 5/6 because of simplicity, features (UMBs, FAT16B), stability and
because I'm used to it.

That's why I'm so hesitantly, I guess. I'd like to do changes the proper way if I can.
This is why I'd like to seek advice from you before I do any changes
(my knowledge about XTs is still little). That beeing said, using an 1.44MB (HD) drive is a neat idea of yours.
If I was building an XT from scratch, I wouldn't have hesitated to install such a drive in the first place.
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Re: PC/XT clone - SFRM72-TU100K or SFR1M44-U100(K) ?

Postby Jo22 » 2018-1-28 @ 12:54

Update. I disassembled the old 720KB floppy drive and cleaned it.
In case you are curious, it is a DFR723F12A from SOLIDWAY INC. :)
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solid01.jpg
solid02.jpg
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

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Re: PC/XT clone - SFRM72-TU100K or SFR1M44-U100(K) ?

Postby Jo22 » 2018-1-28 @ 18:00

Update. Just flashed a SFR1M44 model with the Flash Floppy firmware.
It seems like it works fine in my PC/XT clone so far. :)
See viewtopic.php?f=46&t=58186
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
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Re: PC/XT clone - SFRM72-TU100K or SFR1M44-U100(K) ?

Postby Jo22 » 2018-2-08 @ 09:53

Update. I installed the Gotek in place of the old 720KB drive.
As you can see, the primary drive is still a good old 360KB 5.25" drive.

Mounting the floppy emulator was a bit of a work, though, since the 3.5" to 5.25" frame had outdated specs:
The spaceings for the mounting holes on the sides were that of ancient 5.25" MFM/RLL drives.

And I am talking about the frame itself, not just its inner frame that holds a 3.5" drive!
That's why it was not possible to simply replace that old frame by a modern model from the 90s.

What I finally did, was to use the bottom mounting holes of the Gotek.
They were compatible with the old 720KB drive. :)
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"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

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