Attempting Gotek + FDC+

Discuss construction, troubleshooting, and operation of the Altair 8800c computer

Attempting Gotek + FDC+

Postby mafisher » May 18th, 2024, 1:02 pm

Hello, I am attempting to get a Gotek/FlashFloppy to work with my 8800c + FDC+. FYI a 5.25" drive works. I feel like I am close, but maybe I am deluding myself.

Using PC2Flop.hex everything proceeds normally for the first part of the transfer and write. After the first 445sectors/55k bytes the Gotek indicates it is writing ( W flashes and the track indicator moves from T00.0 to T01.0 ). After the Gotek finishes writing the XMODEM upload seems to stall and I get a "Retry 0: Got 0d for sector ACK" message comes up in minicom.

I tried to upload using Tera Term and I get the same behaviour except Tera Term just stalls and doesn't give any error messages.

Code: Select all
+----------------[xmodem upload - Press CTRL-C to quit]----------------+
|Sending cpm48k.dsk, 2638 blocks: Give your local XMODEM receive comman|
|d now.                                                                |
|Xmodem sectors/kbytes sent: 445/55k                                   |
|Retry 0: Got 0d for sector ACK                                        |
|Retry 0: Got 01 for sector ACK                                        |                                                 
|Retry 0: Got 0d for sector ACK                                        |
|Retry 0: Got 0d for sector ACK                                        |
+----------------------------------------------------------------------+ 


Does anyone see anything that rings a bell?
mafisher
 
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Re: Attempting Gotek + FDC+

Postby AltairClone » May 19th, 2024, 9:07 am

The Gotek has to stall the disk controller during writes to prevent overruns. This is done by stopping index pulses out to the controller for as long as needed. This works fine with most soft sector controllers, but it does not work with a hard sector controller.

The Altair floppy controller (and therefore, the FDC+) is a hard sector controller. Even when using a 5.25” HD-Floppy drive as an 8” replacement, the FDC+ generates fake hard sector pulses. Hard sector disk controllers, in turn, don’t work properly unless the hard sector pulses always occur and do so at the expected rate.

To use the Gotek, you’ll probably have to use a soft sector controller like the Tarbell 1101, a Disk Jockey, etc.

Mike D
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Re: Attempting Gotek + FDC+

Postby mafisher » May 19th, 2024, 10:27 pm

Hi Mike,

thanks for the info, that makes sense. I am glad I didn't pull an all nighter trying to get that working :)

I misunderstood a post here https://altairclone.com/forum/viewtopic.php?f=5&t=321

"The 8” SSSD soft-sector format also allows using Gotek and similar solid-state drives that don’t work well with hard sector disk controllers."

Looking at it again I think it means that if you can run the modified CP/M 2.2 with a 2nd drive controller, that CP/M build can talk to a FDC+ with Gotek?

Thanks, Mark
mafisher
 
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Re: Attempting Gotek + FDC+

Postby AltairClone » May 22nd, 2024, 5:49 pm

Mark,

That post was referring to drive type 8, "FDC+3712" on the FDC+. This mode acts like a soft sector controller and uses the IBM 3740 disk format. In this mode, a Gotek will probably work since it’s soft sector and an extremely common format.

See https://deramp.com/downloads/altair/sof ... /FDC+3712/ for the utilities and disk images you’ll need.

Mike
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Re: Attempting Gotek + FDC+

Postby mafisher » May 23rd, 2024, 11:20 pm

Hi Mike,

Thanks. On my first read through I missed that it is a different version of PC2FLOP. I tried again with the correct version for FD3712 and it got through the formatting on the Gotek and then prompted for the transfer port and sent the first batch of data but failed with "Write failure on track 0, sector 3. Disk creation aborted.". I tried. Even if I did get this working I still wouldn't have a 2nd drive so it isn't the end of the world. Below is the log of the session for anyone who is interested.

Code: Select all
Format the target disk?
  1) Single Density
  2) Double Density
  3) Do Not Format
Select Option or X to exit: 1

Formatting single density disk in drive 0..............................................................................
Format complete

Specify the port to use for file transfer
  1) 88-2SIO port A (which is also the console)
  2) 88-2SIO port B
  3) 88-SIO
Enter 1-3 or X to exit: 2

Start XMODEM send now...

Track/sector not found - disk not formatted?

Write failure on track  0, sector  3. Disk creation aborted.
mafisher
 
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