Linked by Thom Holwerda on Wed 14th Apr 2010 23:51 UTC
IBM This article describes a real-word software port, with examples of how various porting challenges are resolved. If you are a software developer porting software to UNIX, you will find these techniques invaluable in avoiding common pitfalls, resolving bugs, and improving your productivity.
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You have been fooled by IBM marketing. IBM was the first company to employ FUD on a wider scale. IBM is famous for foul play and FUD.,_uncertainty_and_doubt#Definition

Regarding the performance of Mainframes. A z10 with 64 cpus, give 28.000 MIPS. An 8-socket Nehalem-EX gives 3.200 MIPS - under software emulation. Software emulation is 5-10 times faster than native code. If Nehalem-EX could run Mainframe software natively, 8 x86 cpus would give 16.000 - 32.0000 MIPS. You need 8 Intel x86 cpus to match 64 Mainframe cpus.

Mainframes are good for different things, but cpu speed is not one of them.

Also, another source, an Linux expert who ported Linux to mainframes, claimed year 2003, that 1 MIPS == 4 x86 MHz. Hence, 28.000 MIPS corresponds to 112GHz. Pick a 8 core Nehalem-EX, which runs at 2.3GHz = 8 x 2.3 GHz = 18.4GHz. But, Nehalem-EX is much faster clock for clock, than Pentium 4. Whereas 1 MIPS then, is 1 MIPS today. Nehalem-EX may be 2 times faster than one Pentium 4, at same clock speed. Then those 18.4GHz of Pentium 4 MHz, corresponds to todays 36.8GHz. You need just a few of Nehalem-EX to match 28.000 MIPS.

You have two independent sources, who port Linux to Mainframes, or write Mainframe emulators - that states that Mainframe CPU is dog slow.

Also, IBM never publishes Mainframe benchmarks. When IBM has some good number, IBM brags about it all the time. For instance POWER7 is much faster than an Mainframe cpu, and IBM has released POWER7 benches, and brags about it all the time. (POWER7 is a good cpu, Mainframe cpus sucks).

See above.

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