Editing L4 microkernel family (section)

=== University of New South Wales and NICTA ===
Development also occurred at the [[University of New South Wales]] (UNSW), where developers implemented L4 on several 64-bit platforms. Their work resulted in ''L4/MIPS'' and ''L4/Alpha'', resulting in Liedtke's original version being retrospectively named ''L4/x86''. Like Liedtke's original kernels, the UNSW kernels (written in a mix of assembly and C) were unportable and each implemented from scratch. With the release of the highly portable L4Ka::Pistachio, the UNSW group abandoned their own kernels in favor of producing highly tuned ports of L4Ka::Pistachio, including the fastest-ever reported implementation of message passing (36 cycles on the [[Itanium]] architecture).<ref name=Gray_CCMH_05>{{cite conference |last1=Gray |first1=Charles |last2=Chapman |first2=Matthew |last3=Chubb |first3=Peter |last4=Mosberger-Tang |first4=David |last5=Heiser |first5=Gernot |author5-link=Gernot Heiser |title=Itanium: A system implementor's tale |book-title=USENIX Annual Technical Conference |pages=264–278 |date=April 2005 |location=Annaheim, CA, USA |url=http://www.usenix.org/publications/library/proceedings/usenix05/tech/general/gray.html |url-status=live |archive-url=https://web.archive.org/web/20070217224750/http://www.usenix.org/publications/library/proceedings/usenix05/tech/general/gray.html |archive-date=2007-02-17}}</ref> The group has also demonstrated that [[device driver]]s can perform equally well at user-level as in-kernel,<ref name=Leslie_CFGGMPSEH_05>{{cite journal |last1=Leslie |first1=Ben |last2=Chubb |first2=Peter |last3=FitzRoy-Dale |first3=Nicholas |last4=Götz |first4=Stefan |last5=Gray |first5=Charles |last6=Macpherson |first6=Luke |last7=Potts |first7=Daniel |last8=Shen |first8=Yueting |last9=Elphinstone |first9=Kevin |last10=Heiser |first10=Gernot |author10-link=Gernot Heiser |date=September 2005 |title=User-level device drivers: achieved performance |journal=Journal of Computer Science and Technology |volume=20 |issue=5 |pages=654–664 |doi=10.1007/s11390-005-0654-4 |citeseerx=10.1.1.59.6766 |s2cid=1121537}}</ref> and developed [[Wombat (operating system)|Wombat]], a highly portable version of [[Linux]] on L4 that runs on [[x86]], [[ARM architecture|ARM]], and [[MIPS architecture|MIPS]] processors. On [[XScale]] processors, Wombat context-switching costs are up to 50 times lower than in native Linux.<ref name=vanSchaik_Heiser_07>{{cite conference
 |last1=van Schaik |first1=Carl
 |last2=Heiser |first2=Gernot |author2-link=Gernot Heiser
 |date=January 2007
 |title = High-performance microkernels and virtualisation on ARM and segmented architectures
 |book-title = 1st International Workshop on Microkernels for Embedded Systems
 |pages = 11–21
 |publisher = [[NICTA]]
 |location = Sydney, Australia
 |url = http://ssrg.nicta.com.au/publications/papers/vanSchaik_Heiser_07.abstract.pml
 |access-date = 2015-10-25
 |archive-url = https://web.archive.org/web/20150301150250/http://ssrg.nicta.com.au/publications/papers/vanSchaik_Heiser_07.abstract
 |archive-date = 2015-03-01
 |url-status = live
}}</ref>

Later the UNSW group, now at [[NICTA]] (formerly ''National ICT Australia, Ltd''.), forked L4Ka::Pistachio into a new L4 version named ''NICTA::L4-embedded''. It was for use in commercial [[embedded system]]s, and consequently the implementation trade-offs favored small memory size and reduced complexity. The API was modified to keep almost all system calls short enough that they need no preemption points in order to ensure high real-time responsiveness.<ref name=Ruocco_08>{{cite journal
 |last=Ruocco |first=Sergio
 |date=October 2008
 |title = A Real-Time Programmer's Tour of General-Purpose L4 Microkernels
 |journal = EURASIP Journal on Embedded Systems
 |doi = 10.1155/2008/234710
 |volume = 2008
 |pages = 1–14
 |doi-broken-date=1 November 2024
 |s2cid = 7430332
 |doi-access=free
}}</ref>