Help Request on create CP/M for two BigBoards I using DSDD

[enrico]

I would like to implement CP / M or similar with DUAL SIDE DUAL DENSITY disk management and eventually a new BIOS on the following two boards:

A) Clone Bigboard (MK83) equipped with 4MHz Z80A, 32x4116 RAM, Z80ASIO, 2x2716 EPROM and FDC 1797. The board has unknown firmware with entry table to F800H.
B) Bigboard clone (Fabio) equipped with Z80B, 8x4164 RAM, 1x2732 EPROM and FDC 1797. The board has unknown firmware with entry table to F800H.

I have another clone card with Z80 at 2.5MHz, 32x4116 RAM, Z80ASIO, 1x2732 EPROM and FDC 1771. The card has CP / M 2.2 and Russel Smith firmware with entry table to F000H.
Copying the firmware of this card to eprom to be inserted in the first two ones they performe loading the CP / M but of course only in single density.

Thanks in advance for any suggestions.

Enrico

 

[saundby]

If I understand correctly, you need the ROM and the CP/M for an original Big Board I with the 4MHz and Double Density upgrades?

I have original (non-clone) Big Boards with these upgrades. I don't have a system set up yet since my move several months ago, but I might be able to get things set up to do this over the course of a few weeks. I need to set up the BBI as well as the separate system I use to transfer data from it to the internet.

I believe the modifications to PFM for 4MHz were documented in MicroCornucopia, which is all online now. Likewise the DD changes, so that may be quicker for you.

My email address is my user name at gmail, so you can contact me there, if required.

 

[enrico]

Thank you for your answer.


See, if I take the firmware monitor 3.3 and the CP / M 2.2 from my Ferguson Bigboard 1 which mounts an FDC 1771 and install it on one of the other two boards with FDC1797, it loads the cp / m but works only in single density because the firmware system monitor 3.3 evidently has no instruction to manage the 1797 in dual density.


I would therefore need the firmware of a BB1 with 1797 and its CP / M (IMD).


Alternatively I am working on the XEROX SWP image.
I explain to you. Purchased years ago a SWP card that is working perfectly on the Xerox 820-I instead of an FDC 1771 with firmware for single density.
It has instructions for creating your own CP / M. And how does it do it?


1) The PFM 'B' command reads track 0 sector 1 into memory at 0080h and jumps there to start execution of the boot.


2) The boot loader reads track 0 sector 2 into memory 128 bytes below BIOS and reads in the BIOS from sectors 3 through 14. Then control is passed to the code read from sector 2.


3) This secondary loader switches to double density and steps to track 1.
The first 5 sectors on the track contain a new version of PFM with our special I/O handlers. This is read in and overlays the old PFM code at F000h.


4) The PFM overlay code performs a complete reset and re-initialization of all the I/O devices and clears the global variables area at FF00h.


5) Control is passed to the BIOS coldstart address where the CP/M is read in from the rest of the sectors on track 1 (and track 2 if five inch drives).


6) At this point the signon message is displayed and we are up and running.
All system code from the CCP to the top of memory has been booted in from disk, so you are in complete control of the system configuration.


Except that I have problems on how the double density is managed on the cards I have, of which I have no exact wiring diagrams ... For example, I don't know if there is exists the DDEN from FDC to floppy drive.


PS: for the tests I am using 3.5 ”drives that work perfectly in single density but also in double density with SWP card on xerox 820-I.


i do not know how to Attach the SWP instructions.

PS:i tried to send to saundbyx@xgmail.com (without "x2) but it does not work

Enrico