On Wed, 12 Jan 2011 12:21:35 -0600, Avram Friedman wrote:
>One of the things that maide the IBM 360 a sucess was abandonment of the >idea of specialized instruction sets for example geared to Business or Scientific >data processing, NOT BOTH. The Floating-point feature was included for scientific processing. The Decimal feature was included for business processing? Both instruction sets were included so that IBM could market a single architecture suitable for either kind of processing. One factor may have been that they didn't want to have to write and maintain two operating systems on two different architectures. It was not expected that the business users would use floating-point instructions or that scientific users would use packed decimal. >THe 360 instruction set was a marvel. It >actually made it possible to code in assembler with packed arithmatic, even a >pack instruction and there data movement break throughs like the MVCL >instruction. Move Long was introduced with system/370, not 360. >Hardware design changed from >processing one instruction per cycle to pipelining, ie processing parts of >several instructions ever cycle ... I don't know when processors started to pipeline instructions. The 360-91 had a pipelined processor. Early 360 machines did not. >Now the IBM 360 was the worlds worse instruction set for pipelineing. Bold assertion. Do you have any data to back that up? >So why did Amdahl design a plug compatable copy of what was then a known >bad design? Known bad design? Dr. Amdahl was the chief architect of the System/360. He left IBM and started Amdahl corporation because he wanted to extend the series with a higher performance processor and IBM did not think that it would be marketable. And BTW, it was not a "copy". It was a compatible processor, but it was implemented differently. -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
