Wolves in CISC Clothing

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Faster than Native

The FX!32 system represented a major step forward in software based hosting of foreign legacy executables on modern hardware platforms. The resource requirements of FX!32 were also relatively modest, about 140 KB for the transparency agent, 2 MB for the runtime, and 1.5 MB for the translator [8]. Translated native Alpha code was about twice the size of the original x86 code and the original x86 program is retained for legal reasons related to licensing. Performance of x86 binaries executed on Alpha using FX!32 was commonly described as about 70% of native Alpha performance for integer applications and about 50% of native performance for FP intensive applications. This of course would only be after an initial slow run of an application under emulation to give FX!32 an opportunity to collect profile data and perform translation. No doubt some Alpha users failed to appreciate the way FX!32 works and were left with an unfavorable impression of its capabilities after a single run of an x86 application. Nevertheless for about a 6 month period in late 1996 to early 1997, FX!32 on Alpha was actually the fastest way to run many popular x86 based NT applications as shown in Figure 2.

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Figure 2 – Relative x86 Performance: EV56 vs. Pentium Pro

Although executing translated code was 10x more efficient than emulation, FX!32 still used a considerable 4.4 alpha instructions on average per x86 instruction [7]. The higher x86 performance Alpha demonstrates in Figure 2 was the result of the EV56’s 2.5x higher clock rate and moderately higher IPC compared to the Pentium Pro, as well as time spent running within native Alpha OS routines. Unfortunately for DEC, in mid 1997 Intel shifted to 0.25 um production, yielding much faster x86 processors and a 2 year process lead over Alpha. At the same time, Win NT failed to live up to its billing as a Unix killer in the areas of technical computing and engineering which held the greatest potential for Alpha’s performance-at-a-price selling proposition. The dream of wide spread use of Windows on Alpha faded quickly and unfortunately took common knowledge of the impressive accomplishments of the FX!32 team with it.


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