1.0MO5.COMhttp://mo5.com/frrich600338<blockquote class="wp-embedded-content" data-secret="pJnzybrlxK"><a href="http://mo5.com/fr/analysis-the-micral-n-electronic-boards/">Analysis of the Micral N’s electronic boards</a></blockquote><iframe sandbox="allow-scripts" security="restricted" src="http://mo5.com/fr/analysis-the-micral-n-electronic-boards/embed/#?secret=pJnzybrlxK" width="600" height="338" title="« Analysis of the Micral N’s electronic boards » — MO5.COM" data-secret="pJnzybrlxK" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" class="wp-embedded-content"></iframe><script type="text/javascript"> /* <![CDATA[ */ /*! This file is auto-generated */ !function(d,l){"use strict";l.querySelector&&d.addEventListener&&"undefined"!=typeof URL&&(d.wp=d.wp||{},d.wp.receiveEmbedMessage||(d.wp.receiveEmbedMessage=function(e){var t=e.data;if((t||t.secret||t.message||t.value)&&!/[^a-zA-Z0-9]/.test(t.secret)){for(var s,r,n,a=l.querySelectorAll('iframe[data-secret="'+t.secret+'"]'),o=l.querySelectorAll('blockquote[data-secret="'+t.secret+'"]'),c=new RegExp("^https?:$","i"),i=0;i<o.length;i++)o[i].style.display="none";for(i=0;i<a.length;i++)s=a[i],e.source===s.contentWindow&&(s.removeAttribute("style"),"height"===t.message?(1e3<(r=parseInt(t.value,10))?r=1e3:~~r<200&&(r=200),s.height=r):"link"===t.message&&(r=new URL(s.getAttribute("src")),n=new URL(t.value),c.test(n.protocol))&&n.host===r.host&&l.activeElement===s&&(d.top.location.href=t.value))}},d.addEventListener("message",d.wp.receiveEmbedMessage,!1),l.addEventListener("DOMContentLoaded",function(){for(var e,t,s=l.querySelectorAll("iframe.wp-embedded-content"),r=0;r<s.length;r++)(t=(e=s[r]).getAttribute("data-secret"))||(t=Math.random().toString(36).substring(2,12),e.src+="#?secret="+t,e.setAttribute("data-secret",t)),e.contentWindow.postMessage({message:"ready",secret:t},"*")},!1)))}(window,document); //# sourceURL=http://mo5.com/wp-includes/js/wp-embed.min.js /* ]]> */ </script> https://mo5.com/wp-content/uploads/2023/03/IMG_20210405_153231.jpg753525By Philippe Dubois, President. Translation by Sébastien Marty. In this fourth article, we are going to take out the main electronic boards of our Micral N to start referencing them and understanding how they work, then we will dump (copy) its read-only memories (ROMs) in a future article. Our unit visibly contains several RAM boards, one or two ROM boards, a CPU board and several as yet unidentified input/output boards. First of all, we started extracting the boards one by one, taking note of each one’s location. We had no idea at the time how they worked, how they are linked and how they communicate. Rigour is key!   A first board looks interesting to us. It contains 8 ROM – or rather EPROM – chips, recognizable by their small glass windows. A ROM is a read-only, pre-programmed memory, and the EPROM version can be reprogrammed as needed after erasing its contents with ultraviolet light. According to Sylvain Glaize’s analysis of the original Micral N documentation, there is a chance that this board contains the machine’s monitor. That is to say a set of functions that allow you to analyze what the Micral N is doing or in what state it is at any given moment. Regarding the EPROMs used, they are C1702 chips, which are the first production runs available and put on the market in 1971 by Intel. Here’s the Wikipedia page on the subject: https://en.wikipedia.org/wiki/EPROM. You can also find documentation via this link: https://deramp.com/downloads/intel/C1702A.pdf But it is with some dread that we realized their protective glass windows, which should be obscured after programming, are not! We will come back to this later.   The second board we took out is already a bit more mysterious. Firstly, as shown in the photo, it has two connection combs – one to the right and one to the left –, which means that it is probably dedicated to communicating with the outside world. Then, focusing on the central golden chips, we find 8-byte SRAMs referenced as MOSTEK 4007P, whose characteristics are described there:  https://usermanual.wiki.pdf It may be a board used as a buffer, to allow the microprocessor to manage faster data inputs/outputs than it can process. This is a well-known mechanism in computer design, which also takes the name of FIFO queue (First In, First Out) or LIFO stack (Last In, First Out).   This third board is one of the easiest to understand. We are in front of a board comprising 4 KB of RAM (32 x 128 bytes in SRAM 2102 chips) as well as a 256-byte EPROM chip which certainly contains, according to our analysis, the boot code (bootloader) of the machine. That is to say the piece of code to be executed by the microprocessor as soon as the computer starts. Don’t miss our next article, in which we’ll explain how we dumped it – i.e. how we archived its content, which is very important to understanding how our Micral N works!   Finally here it is: the electronic board housing the famous Intel 8008, the world’s first 8-bit microprocessor. It is that tiny golden chip […]