Image Map Image Map
Page 4 of 4 FirstFirst 1234
Results 31 to 34 of 34

Thread: Assembler with Z80 mnemonics

  1. #31


    This is CP/M Plus. The BIOS reads and writes physical sectors and the BDOS does the blocking/deblocking, so a BIOS read will read 1K bytes at a time while the BDOS will read 128 bytes (unless BDOS call 44 is used to set multiple sector reads).

    The issue with the DMA calls was they were using the BIOS DMA call for BDOS reads and writes instead of the BDOS DMA call. I'm now curious as to what the DMA address for the BDOS operations would be if you didn't set it. It looks like it's in the BDOS data area at 82H so I'll check there later. Since it wasn't putting the file in memory where it thought it was (1000H) it was writing garbage to the system tracks.

    You're right that the terms can be ambiguous unless it's specified as "physical" or "logical" and I've seen physical disk formatters that display the current track up from 0 to 79 for DS 40-track drives and others that will display tracks 0-39 and sides 0 and 1 (I used the latter). The DRI documentation didn't help clear up the confusion. For instance, in the documentation I've seen the BDOS call 44 I mentioned says the functions is "BDOS FUNCTION 44: SET MULTI-SECTOR COUNT" and says register E should contain "Number of Sectors". It then goes on to say "The Set Multi-Sector Count function provides logical record blocking under CP/M 3." What they should have called it is "SET MULTI-RECORD COUNT" and listed E as containing "Number of Records".

  2. #32
    Join Date
    Jan 2007
    Pacific Northwest, USA
    Blog Entries


    ...not to mention schemes that involve "zoned" recording, where the number of sectors per track varies.

    CP/M never managed to shake off its beginnings as a simple floppy-based system with IBM 3740-compatible disks. So you wind up with all sorts of work-arounds based on the original. After awhile, the weight of being old gets to be untenable. One wonders how well CP/M would have fared with terabyte disk volumes.

  3. #33


    I tested my new image and it didn’t work. A quick glance through the image file looks like what’s on my current booting disks so I’ll need to dig a bit. It shouldn’t be anything major.

    After I get that fixed then I need to get the disk utility working followed by going through and documenting the console emulations. I have ADM11 and VT52 modes (switchable). There are some limitations in the emulations but they work well enough to run WordStar.

  4. #34


    Over the Christmas break I got COPYSYS working as well as a new disk utility.

    The issue with COPYSYS was due to a bug in my LDRBIOS and original COPYSYS. This bug has been around for over 30 years. I just didn't notice it before since my original COPYSYS was something I wrote as I didn't have the original source. Since the same bug was in both things worked and it wasn't something I had to deal with once I had it working.

    It's now corrected.

    Now to add hard drive support. I couldn't afford a hard drive 30+ years ago. Now I have one so why not? The emulator I'm using to debug has support as well.


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts