<story><title>The IBM Pentium 4 64-Bit CPU</title><url>http://www.cpushack.com/2019/10/01/the-story-of-the-ibm-pentium-4-64-bit-cpu/</url></story><parent_chain></parent_chain><comment><author>hapless</author><text>You may wonder, what was in this for IBM? The answer is fairly straightforward. IBM used to make proprietary chipsets for Intel chips!&lt;p&gt;The pride of the xServer&amp;#x2F;xSeries systems were &amp;quot;complex&amp;quot; setups -- multiple chassis -- with up to 32 sockets, and 512 GB of RAM.  These required a lot of IBM internal engineering, where they made pin-compatible sockets for what Intel was offering at the time, and glued those chips into _hugely_ different topologies than Intel had in mind.&lt;p&gt;These systems sound small today, but back in 2001, this was a really big deal for x86.  The IBM-proprietary chipsets were much more expensive than off-the-shelf systems, but still a fair bit cheaper than going with NCR or Unisys, competing vendors with proprietary x86 MP designs.&lt;p&gt;IBM had a lot at stake when that socket changed.  Achieving pin-compatibility is hard!  Intel is very jealous of their documentation, and prefers to offer paper only, with water-marked copies.  It&amp;#x27;s like owning a gutenberg bible.  Engineering something pin-compatible with an Intel x86 CPU has never been easy.&lt;p&gt;It was no doubt worth it to their &amp;quot;big&amp;quot; x86 server business to ask Intel to make a special run of chips with the old socket layout, but the new emt64 extensions.  I bet it was a complete no-brainer compared to the costs of integrating a new socket!</text></comment>
<story><title>The IBM Pentium 4 64-Bit CPU</title><url>http://www.cpushack.com/2019/10/01/the-story-of-the-ibm-pentium-4-64-bit-cpu/</url></story><parent_chain></parent_chain><comment><author>peter_d_sherman</author><text>Excerpt:&lt;p&gt;&amp;quot;Having such a unique processor at your disposal, it’s absurd not to build a powerful x64-retro system on it.  One of the options for using such a system in general can be to build a universal “PC-harvester” that supports all Microsoft operating systems from DOS to Windows 10.&amp;quot;&lt;p&gt;All Microsoft OS&amp;#x27;es on the same PC?  Cool!  Also, if that&amp;#x27;s indeed the case, my guess is that most versions of x86 Linux and other x86 OS&amp;#x27;es, historic to present, would work too... which is no small feat for a single PC...</text></comment>