IBM Advanced Computer Systems project: Difference between revisions

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In early 1966 the Project Y design was finalized as ASC-1, with the only major change being the removal of the 192-bit extended floating-point format. In 1966, a new building with {{convert|38,000|sqft}} was built at 2800 Sand Hill Road in [[Menlo Park, California]], near the [[Stanford Linear Accelerator]] and the project moved there late in the year. A significant change to the design occurred during this period. Originally, the compiler was responsible for moving instructions out of a large [[core memory]] or [[thin film memory]] store into a smaller cache of [[static RAM]] (although that term was not in use at the time) inside the CPU. Reviewing the system, Schorr and Dick Arnold concluded it would not work, and decided to reimplement it as a single-level with hardware caching of 32 or 64 kWords.{{sfn|Smotherman|Sussenguth|Robelen|2016|p=62}}

Another concept developed for the ASC was dynamic instruction scheduling, or DIS. The ALU and indexing units, which calculated addresses, both had six-slot buffers from which it could select two instructions to execute out-of-order. This allowed the system to execute queued instructions while othersearlier instructions were waiting for data from memory or previous calculations. The outputs from these calculations being executed out of order would then be placed back in memory at the correct time, giving the illusion that everything had been executed in the order it was found in the [[machine code]]. Lynn Conway, who had been hired to develop a software simulation of the ACS, developed a system that used a bit-matrix to track which instructions were ready to be executed and which were waiting as part of the development of a software simulation of the new system.{{sfn|Smotherman|Sussenguth|Robelen|2016|p=62}}

Using the simulator, Conway benchmarked a number of high-performance computing workloads against the [[IBM 7090]], 6000 and [[IBM System/360 Model 91|S/360 Model 91]]. In comparison to the 7090, IBM's older scientific offering, ACS-1 would perform the Lagrangian Hydrodynamics Calculation (LHC) 2,500 times faster. On the more complex Neutron Diffusion (ND) code, it outperformed the 7090 by almost 1,300 times, and was about 60 times as fast as the 6600.{{sfn|Smotherman|Sussenguth|Robelen|2016|pp=62, 66}}