title: Why do we need different CPU architecture for server & mini/mainframe & mixed-core?
body: <p>I was just wondering what other CPU architectures are available other than INTEL &amp; AMD. So, found <a href="http://en.wikipedia.org/wiki/List_of_CPU_architectures" rel="nofollow noreferrer">List of CPU architectures</a> on Wikipedia.</p>
  
  <p>It categorizes notable CPU architectures into following categories.</p>
  
  <ol>
  <li>Embedded CPU architectures</li>
  <li>Microcomputer CPU architectures</li>
  <li>Workstation/Server CPU architectures</li>
  <li>Mini/Mainframe CPU architectures</li>
  <li>Mixed core CPU architectures</li>
  </ol>
  
  <p>I was analyzing their purposes and have few doubts. Taking Microcomputer CPU (PC) architecture as reference and comparing it to others we have:</p>
  
  <p><strong>Embedded CPU architecture:</strong></p>
  
  <ul>
  <li>They are a completely new world.</li>
  <li>Embedded systems are <em>small &amp; do very specific task mostly real time &amp; low power consuming</em> so we do not need so many &amp; such wide registers available in a microcomputer CPU (typical PC). In other words we do need a new small &amp; tiny architecture. Hence new architecture &amp; new instruction  RISC.</li>
  <li>The above point also clarifies why do we need a separate operating system (RTOS).</li>
  </ul>
  
  <p><strong>Workstation/Server CPU architectures</strong></p>
  
  <ul>
  <li>I don't know what is a workstation. Someone clarify regarding the workstation. </li>
  <li>As of the server. It is dedicated to run a specific software (server software like httpd, mysql etc.). Even if other processes run we need to give server process priority therefore there is a need for new scheduling scheme and thus we need operating system different than general purpose one. If you have any more points for the need of server OS please mention. </li>
  <li>But I don't get why do we need a new CPU Architecture. Why cant Microcomputer CPU architecture do the job. Can someone please clarify?</li>
  </ul>
  
  <p><strong>Mini/Mainframe CPU architectures</strong></p>
  
  <ul>
  <li>Again I don't know what are these &amp; what miniframes or mainframes used for? I just know they are very big and occupy complete floor. But I never read about some real world problems they are trying to solve. If any one working on one of these. Share your knowledge.</li>
  <li>Can some one clarify its purpose &amp; why is it that microcomputer CPU archicture not suitable for it?</li>
  <li>Is there a new kind of operating system for this too? Why?</li>
  </ul>
  
  <p><strong>Mixed core CPU architectures</strong></p>
  
  <ul>
  <li>Never heard of these. </li>
  </ul>
  
  <p>If possible please keep your answer in this format:</p>
  
  <blockquote>
    <p><strong>XYZ CPU architectures</strong></p>
    
    <ul>
    <li><em>Purpose of XYZ</em></li>
    <li><em>Need for a new architecture.</em> why can't current microcomputer CPU
    architecture work? They go upto 3GHZ &amp;
    have upto 8 cores. </li>
    <li><em>Need for a new Operating System</em> Why do we need a new kind of operating
    system for this kind of archictures?</li>
    </ul>
  </blockquote>
  
  <p><strong>EDIT:</strong></p>
  
  <p>Guys, this is not a homework problem. I can't do anything to make you guys believe. I don't know if the question is not clear or something else but I'm only interested in just specific technical details. </p>
  
  <p>Let me put a part of  this question in another way. You are in an interview and if the interviewer asks you "tell me, Microcomputer processors are fast &amp; a lot capable and our PC operating systems are good. Why do we need a different architecture like SPARC, Itanium and need a different OS like Windows Server for servers?". What would you answer? I hope got my point.</p>