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Mac OS X

Mac OS X. December 5, 2005 Fall 2005 Term Project CS450 Operating Systems (Section 2) Darrell Hall, Ryan Lanman, Chris Sanford, John Suarez {halldl, lanmanrm, sanforcp, suarezjg}@jmu.edu. OS X History. 1985, CEO Steve Jobs leaves Apple Creates NeXT Inc. NEXTSTEP

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Mac OS X

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  1. Mac OS X December 5, 2005 Fall 2005 Term Project CS450 Operating Systems (Section 2) Darrell Hall, Ryan Lanman, Chris Sanford, John Suarez {halldl, lanmanrm, sanforcp, suarezjg}@jmu.edu

  2. OS X History • 1985, CEO Steve Jobs leaves Apple • Creates NeXT Inc. • NEXTSTEP • based on Mach 2.5 and 4.3BSD • said to be ahead of its time • GNUstep (www.gnustep.org)

  3. OS X History • Meanwhile…Apple encounters problems: • Pink OS fails (joint effort by IBM and Apple) • Advanced OS Copland makes little impact • Considers purchasing • Windows NT, Solaris, and even Pink OS • Steve Jobs pitches NeXT technology to Apple • Apple agrees and purchases NeXT for $427 million dollars

  4. OS X History • NeXT-based system called Rhapsody • Two developer releases • OS X • Announced in 1997 • Mac OS X Server and preview of desktop version become available in 1999 • Mac OS X beta released on September 13, 2000 • 10.0, “Cheetah” released on March 24, 2001 • 10.1, “Puma” released September 29, 2001 • 10.2, “Jaguar” released August 13, 2002 • 10.3, “Panther” released October 24, 2003

  5. The Good of Mac OS X • Aqua’s usability • Excellent FireWire support • Apple's iLife suite (iDVD, iMovie, iPhoto, iTunes, and GarageBand) • Metadata stored in a relation database • Power management • Zero configuration networking

  6. The Bad of OS X • Scattered documentation • System slow down • DVD-R burn errors

  7. OS X Success/Potential • 10 to 15 million OS X ready Macs worldwide • Mac OS userbase: 25 million worldwide • 26% share of US education market • 85% share of US graphics professionals market • > 1 million shrink-wrapped copies of OSX sold • Apple has become the largest UNIX vendor in history • Linux: 12 million users worldwide (linux.org) (Steffen, 2002)

  8. Processor Overview • Two processor modes: • User • Supervisor • Multiprocessor capability • SMP

  9. CPU Scheduling • Preemptive priority scheduling • Priority bands • Normal • System High Priority • Kernel Mode Only • Real Time Threads • “Mach Thread API”

  10. Process States • Process states are actual thread states: • “ready to execute” → ready • “executing” → running • “stopped” → block

  11. System 7-style Virtual Memory • Each page: 4 KB • Processes are given either a 32 or 64-bit virtual address space • 32-bit address can grow to 4 gigabytes • 64-bit address can grow to 18 exabytes • (exabyte = 260 bytes)

  12. VM controls 2 major address ranges • Primary Address Range • Normal memory • File mapping space • Created when Code Fragment Manager is loaded

  13. Figure X: VM address ranges Source: http://developer.apple.com/technotes/tn/pdf/tn1094b.pdf

  14. Implementation • System 7 VM implementation has 5 difficulties: • prevention of fatal page faults • running old drivers • a synchronous SCSI manager • An asynchronous SCSI manager • an ATA manager

  15. Prevention of Fatal Page Faults • Two different approaches: • Stopping paging devices from causing page faults in the process of handling a read/write request • Virtual Memory stops code that may cause a page fault (referred to as “User code”) from executing with another page fault is currently being handled

  16. Old Drivers • Two techniques: • Device Manager routines such as “_Read”, “_Write”, “_Status”, and “_Control” are patched to avoid parameter blocks passed to the device drivers. • The entire system heap is held. • Doing so prevents device drivers from causing a page fault while accessing their own code

  17. Synchronizing the SCSI manager • Solutions: • Ensure the device managers did not cause a page fault • Disable user code while the SCSI bus is busy

  18. Asynchronous SCSI manager • Problem: With the current Virtual Memory Manager, user code quite commonly takes page faults while interrupts have been disabled. However, the asynchronous SCSI manager needs these interupts to complete its operations. • Solution: Patching “vSyncWait” to poll the SCSI hardware looking for interrupts • Not pretty, but it works

  19. ATA manager • When ATA hard disks were intoduced to Mac computers, SCSI software problems reappeared, only for the ATA disks. • Similar problem, similar solution

  20. Bibliography • Steffen, D. (2002). “Mac OS X: The Darwin Kernel.” URL: http://www.maths.mq.edu.au/~steffen/t alks/comp342-macosx-darwin.pdf

  21. Questions?

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