Bit of CP/M trivia needed

Allison ajp166 at
Tue Aug 30 17:13:23 CDT 2005

>Subject: Re: Bit of CP/M trivia needed
>   From: "Dwight K. Elvey" <dwight.elvey at>
>   Date: Tue, 30 Aug 2005 14:29:16 -0700 (PDT)
>     To: cctalk at
>>From: "Allison" <ajp166 at>
>>>Subject: Re: Bit of CP/M trivia needed
>>>   From: "Dwight K. Elvey" <dwight.elvey at>
>>>   Date: Tue, 30 Aug 2005 10:14:15 -0700 (PDT)
>>>     To: cctalk at
>>>>    I don't think so. CPM was first written by Gary Kidall for the Intel
>>>>MDS-800 (go read the CPM docs) and they NEVER had DMA capability. They used
>>>>a 2k bit bootstrap loaded in a 1702 EPROM. Here is a picture of a MDS-800
>>>>with THE actual 1702 Boot EPROM
>>> Yes, what I meant to say was for the S-100. I was told that the first
>>>S-100 implementation used this type of board. I knew Gary used a
>>No.  Most (if not all) of the first S100 system had front pannels 
>>(ALTAIR AND IMSAI Were the first!).  The few that didn't had some form 
>>of rom monitor to simulate a fronpannel via TTY such as Poly-88, 
>>Processor tech SOL and others.
> What does a front panel have to do with what I stated?
> I am familiar with the MDS800 having worked for
>Intel and written both assembly and PLM80 for it.
>I was also responsible for testing of the 1036 card
>( the PLL used in the M2FM board set ). So, I do understand
>the disk I/O of the MDS800. I made no claim as to
>how a MDS800 works( please read previous mails ).
>As I corrected, I was not intending to make a claim about
>the first ever CP/M ( again please read previous mail in
>context ) but felt that from the context of the conversation
>that we were talking about S-100 machines. I tried to clarify
>this misconception that I was talking about the MDS800 in
>a previous mail ( again please read ), I was not talking about
>the MDS800.

Reminising old hardware.  Even the MDS800 was second generation.

> All I'm saying is that I was told that this particular
>DMA based interface was used for the first implementation
>on the S-100 of CP/M. This was told me by another fellow
>many years ago. I don't recall the fellows name but he
>seemed at the time to be honest enough since he had nothing
>to sell or gain by such a comment. He claimed to have some
>involvement in that process. If you don't like that you
>can just shoot me and be done with it but, please, don't
>put words in my mouth.

The first time I'd seen DMA hardware of any kind was 1977
(years after) and it was used for a calcomp platter 
(10mb removable) I was told the system cost 30K$

All the S100 machine of early origin were front pannel
(switches and lights) and few had rom/eprom.  Most all 
used hardware IO and a hand toggled in boot (assuming 
the controller didn't have a bootrom).  Most of the 
people doing it were running far lighter hardware 
than you have there.  Most of the heavey geeks were 
using stuff like PT ALS8 systems to bootstrap to 
CP/M for the first time.  Me I plodded through a 
lot of hand toggling plus my tape based system.
Even then it was load the available image on SSSD 8"
then overlay the drivers by hand (switches or monitor 
program) then save it to whatever before a trial boot.
Early on there were very few disk systems and fewer 
that were plug and go for CP/M.  Usual case was 
migrating from available hardware and non-CP/M software
to CP/M.  Did that for both 8" and NS* 5.25 and also the 
NEC PDA-80 I had.  To this day I cringe when I do a 
first boot even thugh I have moden tools and usually 
boot from EPROM instead.  Such is memory of the process.

It wasn't until around late '77 (same time I got my NS*)
that I started seeing turnkey machines as the norm.  


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