Minimal CP-M SBC design - test-drb@ccmp.vtda.org

10 May 2008

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Subject: Re: Minimal CP-M SBC design
   From: Dave McGuire <mcguire at neurotica.com>
   Date: Sat, 10 May 2008 12:29:24 -0400
     To: "General Discussion: On-Topic Posts Only" <cctech at
classiccmp.org>

On May 9, 2008, at 12:36 PM, Chuck Guzis wrote:
   There is
no requriement to boot the system from "disk"
 and making that change can make bring up simpler. 
 But that's where the "authentic" aspect fails me.   Why run a
 "vintage" CP/M system without the experience a disk drive gives you?
 You'll be deprived of the "BDOS Err on B:" messages.  What fun is
 that?

 One might as well run an emulation program on a PeeCee.  I wouldn't
 be at all surpised to find that someone's done it for the iPod Touch--
 there already exists a NEC 9801 emulator for that platform. 
   I dunno Chuck...the only reason more CP/M systems weren't ROM- 
resident back in the day was due to convention, not technical  
restrictions.  I (personally) don't think there's anything  
non-"period" about ROM-ing CP/M. 
Worked for the PX8 and likely a few others.

Actually the real and most likely reason is you needed 8k or so of 
rom and back when Eprom (or enough eprom) that size was a bit later
and even then expensive for a while. However by around 84ish 8 and 
16k parts were getting reasonable and that is plenty enough space.

Besides booting from rom is like booting from disk, the differnce is 
the rom is read only and doesn't rotate.  Oh it is simpler.

As to "BDOS Err on B:" you can still have that if the system only 
boots from rom and still expects a floppy drive (or other removable 
media).  Personally that is one of the error messages that I can do 
without. ;)

Allison

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              -Dave

-- 
Dave McGuire
Port Charlotte, FL