CP-M Z80 home brew computer circuit board - test-drb@ccmp.vtda.org

15 Jun 2008

...

Subject: Re: CP-M Z80 home brew computer circuit board
   From: "bfranchuk at jetnet.ab.ca" <bfranchuk at jetnet.ab.ca>
   Date: Sun, 15 Jun 2008 11:06:33 -0600
     To: General Discussion: On-Topic and Off-Topic Posts <cctalk at
classiccmp.org>

Andrew Lynch wrote:
  -----REPLY-----

 Hi!  Thanks Jim for the comments.  Please let me address the issues raised
 by Ben:

 If you look closely at the SBC design, you'll notice it has a feature even
 better than a floppy controller -- it has a fully buffered IO bus!  It
 contains all the Z80 signals brought out to the DIN 41612 connector.  The
 peripheral bus adheres to the published ECB standard.

 If you want floppy IO, the solution is simple -- just design one and attach
 it to the bus!  I have already done this with my Disk IO board (IDE and
 NEC765 FDC) which plugs into my home brew ECB backplane along with the SBC.
 Assuming there is enough interest in these home brew SBCs, I hope to make a
 PCB version of the Disk IO board. 
    Well when you get a PCB of the Disk I/O board , I'll take the set of
PCB's.
Will a 8272 (intel) Disk controler replace the NEC765? for the floppy 
controler 
The 8272 and 765 are interchangeable and available.

If you can find a WD37c65 thats far less pars to implement fdc.

Myself I'd suggest to Andrew to not mess with floppy.  Everyone has 
their own idea of what to use and how it should be done and what 
formats it MUST support.

...
 for the track formatting for CP/M? Unicorn Electronics
is my favorite 
shopping for electronic parts and I can find a 8272 there. 
JDRmico has them too.

Having done way to many floppy based sytems and having many on hand
doing something without the noise, power needs and limited space
is a welcome change.  Sonmetimes working with cpm is not about 
floppies but instead the OS itself.

Allison

...

>  
> Yes, this SBC is a slightly modern variation of a vintage Z80 CP/M design.
> I relaxed some of the traditions to make it affordable, reliable, and still
> useful.  The P112, while an excellent design and a wonderful SBC, costs $165
> for a kit when it is available.  I know of no other hobbyist Z80 projects
> where one can purchase the PCB.
>  
> There are many Z80 designs available, however, without a PCB it means most
> hobbyists will have to use temporary breadboards, wire wrap, or prototype
> boards.  None of those lend themselves to long term reliable solutions --
> especially for a wide range of hobbyist builders.
>  
> The SBC PCB is meant to be *low cost* and the *common* element of a home
> brew computer with *simple* IO.  Adding unnecessary and complex IO
> peripherals increases PCB area and cost, raises part count, and pushes away
> the hobbyists it is meant for.
>  
> Selecting IO has to be done very carefully.  Not everyone who builds this
> SBC wants floppy IO.  I have had numerous requests for many forms of IO
> ranging from SCSI, IDE, floppy, CF, SD, USB, the Zilog peripherals, etc.
> There is no solution which will satisfy everyone.
>
> Implementing floppy IO can take on many variations and picking the FDC is
> just the first of many challenges [FDC1793? NEC765? SMC9266? WD2797?].  What
> about the data separator?  Few chips remain and viable sources are scarce.
> Even integrated FDCs with built in data separators are not readily
> available.
>
> Please remember, this is a *home brew* computer project -- a *real* Z80
> running CP/M 2.2 on *real* hardware.  It is what you make of it.  If all you
> want is a PC CP/M emulator then this project is not for you.
>  
> Thanks and have a nice day!
>
> Andrew Lynch
>
>
>    