Re: RE: Minimal CP-M SBC design

> Date: Thu, 08 May 2008 07:50:46 -0400
> From: Allison 

> I can make the boot process easier as you can plop the
rom in 
> mappable space.   The usual arguement is can you get a
Z180
> in a package most people are willing to deal with
(64pin dip)?

I wouldn't want to deal with the DIP as it's a
"skinny" DIP with 
0.050 pin spacing, unlike, say, the 68K.  While it probably
makes 
little difference on a PCB, it requires an adapter if you're

prototyping--and sockets are hard to find.  It's easier to
use the 68 
pin PLCC to keep the spacing--smaller footprint too.

> The latter is the shadow rom many have refered to.  I
usualy do that.
> And make the rom BIG so not only can I map it in when I
want but also
> access part of it  (ROMDRIVE).

I believe the Amstrad Joyce uses the printer controller to
force the 
necessary boot code onto the Z80 bus.  (Tony?)  At least
I've never 
seen a boot ROM on a Joyce PCB.  

> 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. 
 

> Deblocking is not too mysterious.  The real missing bit
in the 
> Alteraion guide is how the BDOS telegraphs the need to
preread 
> and when to skip it.  

Page 14, section 12 entitled "Sector Blocking and
Deblocking" in the 
Alteration Guide covers it pretty well.  I remember being
relieved to 
find the information after I struggled with 1.4 not having
any such 
mechanism.  I don't think it was in 2.0 either, but I can
check if 
anyone's curious.

Cheers,
Chuck

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.

              -Dave
>


-- 
Dave McGuire
Port Charlotte, FL