CP/M load question - test-drb@ccmp.vtda.org

11 Mar 2013

On 03/11/2013 02:01 PM, Enrico Lazzerini wrote:
...
  Hi at all, I'm sorry I'm not very prepared and
my English is basic.

 I have a mainboard with CPU Z80 derived from the famous Ferguson Big Board 1
 (that i have working fine). It has a CPU Z80A running at 4MHz, 64KByte DRAM,
 FDC 1797 with external data separator FDC9228BT. It equipped with its own
 BIOS that is loaded into memory at address F800H but it not has the
 operating system CP/M.

 If instead of his eprom i insert the firmware coming from Ferguson Bigboard
 1 (which is loaded into memory at address F000H) that has FDC 1771 it run
 properly loading the operating system CP/M 2.2. I looked in my experience
 and modified the CP/M loader and CBIOS to point at the entry points of the
 bios at F800H, so the loader loads into memory correctly ALL the CCP, the
 BDOS and CBIOS, but it not complete the boot CP/M with the prompt (the error
 that comes to me is: track 2 sector 1 not found. it is an area where
 normally there is no CP/M code and that it is regularly read with a simple
 read command available from the firmware). 
This is difficult as the problem is clear that you have a FDC related 
hardware issue.
The error occurs when CP/M starts up and attempts to "log the disk in" 
or generate
a map of the directory.  Its failing to read a valid directory likely 
due to the
differences between 1771 and 1797 or possibly a bad sector on the media.

Note the directory must be cleared (initialized) to all 0xE5.

I cannot say what emulator would work best for you.  I debug problems 
like this
using a resident monitor rom and instrumented code (lots of messages).

Allison

...

 I ASK FOR: Anybody has any idea? Is there a Z80 emulator where I can load
 the BIOS and i can try to load the operating system CP/M to see what type of
 problem?

 Regards

 Enri