Memory: the flat, the discontiguous, and the sparse

Posted May 28, 2019 7:48 UTC (Tue) by bgoglin (subscriber, #7800)
Parent article: Memory: the flat, the discontiguous, and the sparse

>> making the change for such architectures as ia64 and mips64

Does anybody really still use ia64? except maybe HP-UX servers?

Memory: the flat, the discontiguous, and the sparse

Posted May 28, 2019 12:22 UTC (Tue) by ncm (guest, #165) [Link]

If I remember right, the New York Stock Exchange and the Sabre flight reservation system switched wholesale to Linux on Itanic some years ago. They might still be on it.

One can imagine HP-UX users migrating to Itanic emulations running Linux with an HP-UX compatibility layer, hosted on Linux amd64.

It is the norm, nowadays, for enterprise software to be running on several layers of emulation, yet still running faster than on the original hardware. Emulators tend to be, themselves, the least portable of code, so they are, ironically, the first candidates to be emulated instead of ported.

There are only two outcomes from any migration or upgrade of legacy code: it still works, or it doesn't work. So, people responsible for legacy systems become risk-averse. Emulation is less risky than porting, even with a wobbly tower of emulations. Emulating big-endian platforms on little-endian hardware is surprisingly practical.