Included in 2003-2004 correspondence from Bruce Jones for software fixes to his Dec 2003 SD System software,
is this note about VF II hardware jumpers. The complete correspondence is in my "/herbs_stuff/sdfix.html" document.
Much more VF II documentation and code is in my "herbs_stuff/s_sd_vfii.html#vfii" document. 
- Herb Johnson, retrotechnology.com 

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On Mon, 5 Jan 2004 12:56:08 -0500, "Bruce Jones"  wrote:


** Small Hardware Change Note for VF-II **

I just received [a Versafloppy II controller card].

This should be the last change note.

I prepared the VF-II for operation, and it would not boot. I had to add a
jumper to get it operational.

Here is the change:

On U15 solder a jumper wire from pin 11 to Ground.

This is the RDY* (negative true) signal from pin 22 on the 8" drive
connector.

5.25" and 3.5" drives don't have a connection for this, so, it will always
make the drives look busy. In addition, I wrote the BIOS, XIOS and BOOT code
to work with this always grounded.

Since this line is a pull-up on the VF-II board, and since it is driven by
an open-collector
device from the floppy drive, shorting to ground is OK.

I learned back in 1980 that setting this always true for 8" drives was not
only OK, but necessary. Myself and some of the applications programmers
noted that 'false' drive-not-ready errors would randomly pop up, depending
upon the drive brand and model, and the seek pattern, if the RDY line was
kept 'normal'. The commands used by the BIOS, XIOS and format software work
just fine without the floppy drive controlling this line.

I have now run the [new] VF-II in the following modes:

- PIO only, no interrupts
- DMA with interrupts

I have run it so under CP/M and MP/M, just fine.

I have also run the disk format software OK as well, so that covers all the
functionality.

One other thing is the strange cross-jumpering of E8-E9. I guess that was an
SD Systems mod for their OS driver. I do straight-thru jumpers (E7-E8 &
E9-E10) for FDC end-of-operation interrupt and DMA DRQ signals. But it would
only be an issue, which I would explain, if anyone runs MP/M or the BIOS
with a Z80-DMA and interrupts. The BIOS code for DMA use is not issued,
since we decided to just make a BIOS that worked with the VF-II and most
CPUs, but anyone looking at the [MP/M] XIOS would see the conditional
assembly for it, however I see you have not posted that code.

Best regards,
Bruce Jones