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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif"'>This was part of an earlier discussion in this forum. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif"'>I want to correct the impression created by Lawrence D'Oliveiro that those who implemented stacks were not designing for efficiency. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:blue'>> What I can say is that for scientific/engineering calculations the RPN of<br>> KDF9 was Great because assembler was no harder than using algol60 for the<br>> calculations part of the problems I worked on.</span><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><br><br></span><b>Lawrence D'Oliveiro</b> <a href="mailto:python-list%40python.org?Subject=Re%3A%20Good%20books%20in%20computer%20science%3F&In-Reply-To=%3Ch1mo5n%24dlq%243%40lust.ihug.co.nz%3E" title="Good books in computer science?">ldo at geek-central.gen.new_zealand </a> Mon Jun 22 03:52:55 CEST 2009<span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:#365F91'>Unfortunately, we had to learn the hard way that machine instruction sets<br>must be designed for efficiency of execution, not ease of use by humans.<br>Stack-based architectures, for all their charm, cannot match register-based<br>ones in this regard.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>FWIW: “Efficiency” is a slippery notion with contextual connotations. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>KDF9 had two stacks in its CPU. (The SJNS and the Nesting Store or Nest – see Eric’s thesis.)<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>I am not suggesting that you are ill-informed, but that stacks are insufficiently represented in the literature. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>The use of call return stacks to support subroutine returns is almost universal. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>For the evaluation of arithmetical expressions, the use of hardware stacks is the most efficient. From what I have read, it is compiler writers who find it hard to emulate the efficiencies achieved by assembler programmers. Are hardware designers considering the compiler writers’ problems when they design their hardware? This would be heavy irony indeed. That is why stacks came into existence in the first place.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>Regards,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>Phil<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:blue'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>References:<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><a href="http://is.uwaterloo.ca/Eric_LaForest_Thesis.pdf"><span style='color:black;text-decoration:none'>http://is.uwaterloo.ca/Eric_LaForest_Thesis.pdf</span></a> discusses the confusion of first and second generation stack-based architectures. It includes a rebuttal of the arguments against stack computers, cited by Hennessy and Patterson, showing that they are applicable to the first generation of stack computers, but not the second. <o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'>Christopher Bailey’s “Optimisation Techniques for Stack-Based Processors”, PhD thesis, University of Teesside, UK, July 1996, Amongst other things, analyzes the use of stack buffers to reduce memory traffic.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Verdana","sans-serif";color:black'><o:p> </o:p></span></p></div></body></html>