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RE: [N8VEM-S100:4058] My first S100 computer is alive !

Hi Philippe

That's great! Another Z80 lives again! :)

My advice, get I/O and start talking to it through monitor programs, and/or write your own monitor.  When getting my IMSAI running, writting my own monitor was a lot of fun.  A modified copy of it is available on the wiki site under my new board, you would just have to change the routines that read/write to the UART.

Now, I don't know what other I/O boards do, but most I've seen use the +/- 16V for the RS-232 driver.
I know the 8080 boards needs the +/- 16V for the 8080A chip.  I don't think it's so critical, I bet a couple of wall warts would do the job.

Josh Bensadon


Date: Mon, 9 Jun 2014 09:03:44 -0700
From: philip...@gmail.com
To: n8vem...@googlegroups.com
Subject: [N8VEM-S100:4058] My first S100 computer is alive !

Hello all,

thanks to your recommendations and helpful feedbacks, I managed to get a *very* basic S100 system running :) I really mean basic, as it only consists in :
- a backplane (passive one, a Salota board I got from eBay)
- a switched power supply (so far I only use the +7.5V one)
- a Z80 Ithaca 1.03 CPU board I got from eBay

I confess I wanted to try myself on completed boards before I start building the cards myself, and I think that was quite interesting... I purchased a scope, an Openworkbench Logic sniffer, both are great and allowed me to debug the Ithaca card that showed several bad solders. I also modified the board to replace the 2708by a a 2732 (my EPROM programmer is unable to program the 2708 and this chip also requires -16V and + 16V I do not plan to install considering these voltages are not needed by the vast majority of boards)

I installed the boards and PS on a temporary aluminium frame, until I migrate the whole shebang into the case I received from modushop : 

I debugged the board as it is advised on s100computers.com : a PROM containing HALT instructions, and then a loop containing I/O's. It took me some time to realize how the jump on reset circuitry works and identify that several DIP switches were faulty, but I finally got this working :
ORG 0F000H
LD B,04H
OUT (0H),A

In the meantime, I ordered some literature (the 7 volumes of S-100 Journal and "Interfacing to S-100 .." by S. LIbes / M. Garetz) and last but no least, several boards from N8VEM : CPU V2, ZFDC, SIO, IDE, SMB, Extender, motherboard, 4Mb RAM, and ROM/RAM. 
I already received SIO, IDE, and I am impressed by the quality of the PCB's !

I would like to get your advice about which card do you think I should start with ? I am considering building the Serial IO at first as this would allow me to continue the debugging, or would the SMB make more sense ?
thanks for your inputs and recommendations, I am really glad I joined this forum !


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