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Disabling internal FDC on Tandy 1000 TL/2

bjt

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Jun 18, 2013
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I've run up against a problem using a HxC Gotek with my TL/2's internal FDC. Reading works fine, but not writing - it's like the Gotek just doesn't receive the write signals. Have confirmed it working with a real floppy drive, so it's definitely the Gotek at fault. Tried a second Gotek too.

Using an ISA FDC should cure this, but I need some way to disable the built-in FDC. The TL/2 has a FDC disable option in SETUPTL /A, but the readme for the NOFLOPPY utility says it doesn't work. NOFLOPPY is a small program that toggles some bit to disable the internal FDC and allow an ISA FDC to take its place.

The downside of NOFLOPPY is that you obviously need to boot first, so no booting from the ISA FDC.
Perhaps it's possible to toggle the same bit that NOFLOPPY does from within expansion ROM code (e.g. XT-IDE booter) to allow booting from an ISA FDC?

Thoughts welcome and I'll post here with my findings. Thanks
 

bjt

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Quick update... NOFLOPPY writes f7 to port 65h. Would be trivial to stick this in the XT-IDE bios just before boot.
 

Cloudschatze

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Before trying anything else, and with the Gotek on the internal floppy header, you might try adding "DRIVPARM=/d:0 /f:2" to the CONFIG.SYS file, and see if that resolves the write issue.

I don't believe that NOFLOPPY is needed for the TL/2 (I'm not using it). You can verify by reading the initial value from that 0x65h planar control register, then disable the floppy controller using the "SETUPTL2 /A" utility, and then reboot and re-read from the register to see if bit 3 has changed.
 
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Chuck(G)

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That's odd. The TL/2 uses a standard (i.e. NEC-design) FDC, so its behavior shouldn't be any different from any other PC using a 765 derivative. I wonder if there's an issue with the drivers on the TL/2. Is there perhaps a schematic somewhere?
 

bjt

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Yes, it is strange. The developer of the HxC firmware for Gotek thinks it's some filter setting on the incoming WDATA signal.
Good to hear that NOFLOPPY may not be needed on the TL/2.
 

bjt

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Update - with a fixed HxC firmware, the Gotek now works fine with the TL/2's onboard FDC. I understand the problem was some kind of filter setting based on the length of the WDATA pulses.
 

mojorific

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Update - with a fixed HxC firmware, the Gotek now works fine with the TL/2's onboard FDC. I understand the problem was some kind of filter setting based on the length of the WDATA pulses.

Could you explain how you fixed the hxc firmware? Also, if you have a copy of it, I would be interested for my TL/2.

Thanks.
 

bjt

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Could you explain how you fixed the hxc firmware? Also, if you have a copy of it, I would be interested for my TL/2.

Thanks.

Jeff (HxC creator) sent me a firmware with the fix. It may be in the next public release, or you could email him at hxc2001@hxc2001.com to ask for it.
 

keenerb

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Quick update... NOFLOPPY writes f7 to port 65h. Would be trivial to stick this in the XT-IDE bios just before boot.

Sorry for replying to such an old thread, but I just had the same idea, and a search led me to this comment.

Were you ever successful at including this little bit of code in the XT-IDE bios? I'd love to be able to use a high-density floppy drive as a boot device on my 1000TL.
 

keenerb

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I was able to include the commands to disable floppy drive in a custom XT-IDE bios. I look forwards to booting directly off a high-density drive in my tandy 1000tl this evening...
 

Thallanor

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Sep 16, 2018
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I understand that this is an older thread, but it pertains to disabling the FDC on the Tandy 1000 TL/2. Has anyone experienced, or know what might cause to happen, when running 'nofloppy,' returning to the DOS prompt but doing anything, even a simple 'dir' command, displaying text corruption? What's more strange is it's not random text but strings of text as follows:
DSC_0703.jpg
At that point, the system is now locked up as well. Usually get a couple beeps too. I'm totally at a loss. And until I get this to work, I can't even try seeing if my ISA FDC I bought will work or not. I'm kinda actually leaning towards 'not' as I don't think it has a BIOS extension or anything on it.

Anyway, I can create this in a new thread if that makes sense. Just thought I'd give a poke to this thread first.

P.S. I noticed here that you did manage to add the bits and pieces to your ROM to get it to disable the built-in FDC that way. Are you able to share how one goes about doing that? I'm about to order my Lo-tech XT-CF adapter and if I could do all of this through that, that would be much cleaner.

Thanks so much in advance!
 

Thallanor

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I'm just giving a little poke here in hopes that someone more a Tandy expert than myself might have some insight. I'm dead in the water with this build until I can find away to disable the built-in FDC. :( The only other option that might work would be finding an 8-bit SCSI adapter with the appropriate ROM so that I can boot from it (assuming that is possible) and then paying an arm and a leg for a SCSI floppy drive. :(
 

Thallanor

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Sep 16, 2018
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I don't believe that NOFLOPPY is needed for the TL/2 (I'm not using it). You can verify by reading the initial value from that 0x65h planar control register, then disable the floppy controller using the "SETUPTL2 /A" utility, and then reboot and re-read from the register to see if bit 3 has changed.
While this is an old thread and my question isn't about the Gotek specifically, I was wondering how I would go about reading the 0x65h PCR? The reason I ask is that when I run nofloppy, I get artifacts on the screen before my TL/2 locks up and beeps. I was going to see if setuptl2 /a results in a change to the PCR on my TL/2. And a n00b question: what is the PCR normally used for? I'm just trying to narrow down what is causing the lockup. I'm running the Tandy ISA VGA card on this system, if that makes a difference. I was going to start pulling all of my cards to see if something was causing the lockup when nofloppy was run, but my Tandy monitor for TGA graphics is at my parents place still, so I wouldn't be able to see anything after booting if I don't have the VGA card installed. D'oh!
 

Thallanor

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Sep 16, 2018
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debug.exe
-i 0x65
[value]
-q
Thank you so much! Will fire it up in a little bit. I should have remembered this. And is it -o to write to a port address? I cannot remember the exact syntax. :( I'm just curious if I can find that for whatever reason on my TL/2 if setuptl2 changes it to something else, if I'm able to poke it with a stick on boot and see if it'll disable it. :)
 

moz_21

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Jul 28, 2019
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I was able to include the commands to disable floppy drive in a custom XT-IDE bios. I look forwards to booting directly off a high-density drive in my tandy 1000tl this evening...

I'm very interested in knowing how this was accomplished.
 
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