[Simh] altairZ80 floppy disk binary files

Mon Sep 22 20:28:18 EDT 2014

Hello!
I'd say you've managed to obtain a for real wowser there. The boards
are amazing. One of them, according to the Wikipedia page, probably
the Xerox 820 also used one of the BB2 devices.

I have here an oddball in a standard S100 box, I've been in the
process of restoring for the past several years. So far all I can
discern about it is that it's originally a microprocessor trainer for
the I8080 processor.

And from what I recall about the software you're working with then yes
you do need to do that.

I suggest you take a look at the Xerox 820 just for backup purposes,
that is to support your work.

Too bad you're over in your part of AU I'd love to see your work....

Good luck and all of that.
-----
Gregg C Levine gregg.drwho8 at gmail.com
"This signature fought the Time Wars, time and again."

On Mon, Sep 22, 2014 at 8:17 PM, Malcolm Macleod <malcolm at avitech.com.au> wrote:
> Hi Gregg,
>
> The original Ferguson Big Board ("BB1") was released in about 1980.  It's a single-board computer running CP/M 2.2.  It has 64KB of onboard dynamic RAM, a 2.5MHz Z-80 CPU, 1771 FDC and on-board 80x24 video.  It has the same footprint as an 8" floppy drive.  There's a Wikipedia page on it -> http://en.wikipedia.org/wiki/Ferguson_Big_Board
>
> I was aware of the BB1 when I was a kid.  But never owned one at the time.  I acquired 3 of these (2 x BB1, 1 x BB2) a few years ago.  One of these was mounted in a homebrew aluminium case with two full-height 8" drives.  It came with boxes of 8" floppies, and I'm working my way through those and learning about the original-owner's modifications to the on-board monitor ROM and to the CP/M CBIOS (which is also in the ROM).  My immediate goal is to further modify the CBIOS to work with 3.5" drives (in place of the 8" drives).  I've already got it working with single-sided 3.5" disks. The problem is that the CBIOS looks for a signal from the 8" drives (which the 3.5" drives don't have) to determine whether a single-sided or double-sided disk in in the drive.  So I want to modify this code to make it not dependent on the input signal.
>
> Malcolm.
>
> -----Original Message-----
> From: Gregg Levine [mailto:gregg.drwho8 at gmail.com]
> Sent: Tuesday, 23 September 2014 9:25 AM
> To: Malcolm Macleod
> Cc: simh at trailing-edge.com
> Subject: Re: [Simh] altairZ80 floppy disk binary files
>
> Hello!
> Malcolm, what is a Ferguson Big Board ROM? I mean obviously its the board's ROM array, but what is a  Ferguson Big Board to begin with? Is it a computer that ran the OS back when such things were more commonplace?
> -----
> Gregg C Levine gregg.drwho8 at gmail.com
> "This signature fought the Time Wars, time and again."
>
>
> On Mon, Sep 22, 2014 at 7:14 PM, Malcolm Macleod <malcolm at avitech.com.au> wrote:
>> Hi Peter,
>>
>> Thanks for the fast response.
>>
>> That worked, when used with the SIMH command "SET HDSK1 FORMAT=SSSD8S".
>>
>> Note that I needed to use altairZ80.exe downloaded from your site for this to work (ie "V3.9-0 build 1625").  The Windows executable of V3.9-0 downloaded from the main SIMH site generated errors mounting the IMD file.
>>
>> FYI - I'm using altairZ80 to rebuild a Ferguson Big Board ROM from source.  AltairZ80 is a great platform for this work.  Thanks for making it available.
>>
>> Malcolm.
>>
>> -----Original Message-----
>> From: Simh [mailto:simh-bounces at trailing-edge.com] On Behalf Of Peter
>> Schorn
>> Sent: Tuesday, 23 September 2014 3:03 AM
>> To: simh at trailing-edge.com
>> Subject: Re: [Simh] altairZ80 floppy disk binary files
>>
>> Hi
>>
>> 1. The file format for the AltairZ80 DSK device is basically a sequence of 77 tracks with 32 sectors of 137 bytes (CP/M 2 can also handle disks with 254 tracks). This is modeled after the FD-400 hard-sectored floppy drive.
>>
>> 2. If you want to mount an IMD disk under CP/M 2 use the cpm2.zip from
>> here http://schorn.ch/cpm/zip/cpm2.zip and use the command
>>
>> attach hdsk1 <yourfile.imd>
>>
>> to mount the IMD file "yourfile" as disk J:
>>
>> Note that the BIOS of the supplied CP/M 2.2 only supports 128 bytes
>> sectors. I updated cpm2.zip to include cpm2_imd which demonstrates
>> this
>> - just use altairz80 cpm2_imd and a blank SSSD 8” IMD will be mounted on drive J:
>>
>> Peter
>> -----
>> peter.schorn at acm.org
>>
>>
>> On 22.09.14 14:32, Malcolm Macleod wrote:
>>> A couple of questions about virtual-floppy-drive files under altairZ80.exe:
>>>
>>>
>>>
>>> 1.           SIMH’s file-format for representing floppy drives
>>>
>>>
>>>
>>> Can anyone point me to some information about the file-format for
>>> Floppy Disk Drives in altairz80.exe under SIMH ??  Section A.2 of
>>> Appendix 1 of “simh_doc.pdf” says that: “Floppy disks are represented
>>> as unstructured binary files of 8b data items. They are nearly
>>> identical to the floppy disk images for Doug Jones' PDP-8 simulator
>>> but lack the initial 256 byte header. A utility for converting
>>> between the two formats is easily written”.  However, I’ve not been
>>> able to find a description of how these files are structured.  For
>>> example, I’ve noticed that when I create a blank disk in
>>> altairz80.exe (eg by using the command “ATTACH
>>> DSK1 NEW.DSK”, then formatting it using FORMAT.COM on the supplied
>>> CPM2
>>> disk) that the floppy disk file seems to have an extra 9 bytes
>>> between the actual sector data, so it doesn’t seem to be just raw sector data.
>>>
>>>
>>>
>>> 2.           How do I mount ImageDisk (IMD) disk images under altairz80?
>>>
>>>
>>>
>>> The “AltairZ80 Simulator Usage” PDF (altairz80_doc.pdf) makes
>>> reference to IMD files being supported, but I’ve not been able to
>>> find any information about how to do this.  For example – if I want
>>> to mount an existing CP/M 2.2 SSSD 8” IMD image, with 26 x 128 byte sectors, as B:
>>> (under altairz80.exe), how do I do this?
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Malcolm.
>>>
>>>
>>>
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