Lecture No. 4

1. Lecture No. 4 Memory and its Management Operating Systems 2000 and XP

2. This Lecture Last week, we started to look at some of the ‘internals’ of PC (mainly) hardware and software - mostly at Operating System and Hardware CPU level This week, we are going to have a slightly deeper look

3. Memory/Memory Management Personal Computer Memory: - at DOS system prompt, key in mem/c ************************** Conventional memory: Up to the first 640Kb of memory. All MS-DOS based programs require conventional memory Upper Memory Area : 384Kb above the 640Kb of conventional memory Used by System Hardware (display adapter) UNUSED parts of upper memory are called upper memory blocks (UMB’s). Used for running device drivers and memory resident programs

4. Memory/Memory Management Extended Memory (XMS): Beyond 1Mb ( 286,386,486) Requires an extended memory manager (HIMEM.SYS) Windows and Windows based applications require extended memory High Memory Area : First 64Kb of extended memory. (MS-DOS is normally loaded here. Leaves more conventional memory available)

5. Memory/Memory Management Virtual Memory: Space on the system hard disk which is used by Windows as if it were ‘normal’ high speed memory Expanded Memory (EMS): Installed on the system expanded - memory board, uses an extended memory manager. Available in 64K blocks - EMS page frame Slower than using extended memory.

6. Memory/Memory Management 3Mb 16,32,64,128 ... ? Mb Extended Memory (XMS) (2Mb) Expanded Memory (EMS) (1Mb) HMA 1Mb Upper Memory Area (384Kb) Conventional Memory 640Kb (640Kb)

7. Other Storage Matters The amount of ‘high speed main memory’ is limited. The limiting factors are size related to the volume of data required to be stored, addressing capability and of course, cost One of the major aims of a computer is to provide fast processing/throughput A limiting factor is the ‘retrieval’ of data from secondary storage (disks, CD-Rom, DVD, ….)

8. Other Storage Matters However, once data in is the ‘high speed storage’ area, there are a few ways of improving process capability One method is to have ‘Cache Memory’ - this is a copy of data which was • retrieved from secondary storage (disk or CD Rom), • placed in Random Access memory (RAM) • retrieved from RAM for process purposes by the CPU, • AND a copy of the ‘record’ or ‘data element’ is placed in Cache Memory.

9. Cache Memory If the ‘data’ is required again, the first search is to Cache Memory There are 2 major types of Cache Memory • Internal Cache - built into the CPU chip • External Cache - is located on SRAM chips close to the CPU on the system board • Cache Memory can be from 1Mb to 2Mb

10. Cache Memory The pattern of search is • - 1. internal cache • - 2. external cache • - 3. main memory • and then to secondary storage (disk, CD-Rom , DVD….)

11. Memory Chips 2 Basic Types • 01. Random Access memory (RAM) (volatile) SRAM (static RAM - refresh not necessary) DRAM (dynamic RAM - needs refreshing - slower than SRAM)

12. Memory Chips • 02. Read Only Memory (ROM) (non volatile) Also, not able to be altered by the user (Other variations PROM, EPROM

13. Memory Chips Another less obvious chip also exists: • CMOS - Complementary metal oxide semiconductor • Requires only low power. Holds setup details - supplemented by Autoexec and Config data

14. More Chip Types DRAM - dynamic RAM FPM RAM - Fast page-mode RAM EDO RAM - Extended Data Out RAM BEDO RAM - Burst Extended-data-out RAM SDRAM - Synchronous dynamic RAM SRAM - Static Random Access Memory Async SRAM - Asynchronous SRAM Sync SRAM - Synchronous (with the system clock) PB SRAM - PipeLine Burst SRAM VRAM - Video Ram WRAM - Windows RAM SGRAM - Synchronous RAM DDR DRAM - Double Density Read RAM

15. More Chips • FPM DRAM – Fast Page Mode D Ram • PC133 SDRAM – Bus speed 133mhz • 1T-SRAM • Direct RDRAM – Read DRAM • SDRAM is about 3 times faster than FPM RAM • And about twice as fast as BEDO DRAM • SDRAM is replacing EDO DRAM in newer PCs

16. SIMD • SIMD = Single instruction, multiple data • Mostly for multimedia • Relate to a single command which is executed on each piece of data in a set (for example, an image) • increasing/decreasing the • intensity • colour • volume of an object • or using comparator functions to determine equality/non-equality of 2 or more objects

17. More Memory Detail • Wednesday 31st March (next week) is the HECS census date for Semester One • It is also the last day to discontinue Semester one or full-year units without ‘WD’ showing on your Academic Record • And it is the last day to discontinue Semester 1 or full-year units without incurring HECS or full-fees relevant to Semester 1 • It is the last day to discontinue all studies by candidates enrolled coursework programs and in single units to qualify for a full refund of the student course fee for Semester 1 • It is the last day for a 100% refund of student amenities fees relevant to Semester 1

18. Travelling Around the Computer So, how does ‘data’ (in all of its various forms and meanings) get around the various devices ? No problem It takes a bus So, what is a bus ? It is an electronic path in a computer system which transmits bits - the binary digits which represents the atomic values of data

19. Travelling Around the Computer There are a number of different varieties of ‘buses’ 1. The Internal Bus - its function is to move data around the CPU chip 2. Data and Expansion Buses - their function is to link the CPU and RAM to extend the data bus and to establish links with peripherals

20. Travelling Around the Computer 3. Local buses - a special bus (or buses) which link peripherals requiring fast response times (display, disk, high speed local networks) (GUI’s, Multimedia, scanners - all have high bit loads and require fast traffic lanes) 4. Universal Serial Bus - capability of linking many devices to a single or common port (such as the Zip drive, pluggable hard disk, CD-Rom)

21. More on Buses • PCI = Peripheral Component Interconnect (McIntosh) • VESA = Video Electronics Standards Association • MCA = MicroChannel Architecture (IBM PS/2) • EISA = Extended Industry Standard Architecture • ISA = Industry Standard Architecture (ISA is 16 bit (binary digit). The others are 32 and 16 bit)

24. Windows 2000 / XP These are current microcomputer operating systems, and provide a user, like yourselves, with a graphics user interface (gui) This interface lets you select - an icon, which normally has a text box attached to it and which MAY initiate a program - Netscape - a menu (and sub-menu) function or set of functions - an application such as Word, Excel, …...

25. Windows 2000 / XP • An icon is a GUI macro - its selection causes the computer to start (or stop) a series of processes. • These processes are supported by software, and this software is encapsulated in different types of files Some of the common ‘active’ files are recognised by their extents: .exe - executable .com command .bat batch

26. Windows 2000 / XP Data content file extents indicate to the ‘process’ function the way in which the data has been recorded A Word file will have an extent of .doc An Excel file will have an extent of .xls (or a variation) A PowerPoint file will have an extent of .ppt A MS Access database file will have an extent of .mdb Other ‘data’ may be pictures or objects Their extents can be .jpeg, .pif, .wav, gif and so on (don’t forget the html, and htm variations)

27. Windows 2000 / XP Windows 2000 and XP have a ‘Registry’ - also known as ‘Intelligence’ The Registry is the database for all system information. The registry contents can be altered - but be very careful - and if you really have to alter the Registry, back it up first

28. Windows 2000 / XP Registry editors must be used - be very, very careful ! All of the GUI administration tools serve as ‘front-ends’ to the registry and store all their data in it. An important and powerful feature of the Registry is the ability to read in Registry settings from datafiles. (‘Active’).

29. Windows 2000 / XP There are 4 primary ‘consumers’ or ‘customers’ of the Registry • The Windows operating System • Software installed on your computer • Hardware installed on your computer • You - the user

30. Windows 2000 / XP Windows 2000 and XP • Have no Registry size restriction • Are hierarchically arranged • The Registry contains standardised values • User information is stored in HKEY_USERS keys • The Register can be remotely administered • System policies (e.g. upgrades) can be downloaded from a central server each time a new user logs on can this be correct ?

31. Windows 2000 / XP The Registry is a central repository for hardware-specific information which is used by the Plug and Play system components. Windows 2000 and XP hold and maintain information about hardware components and devices which have been identified by processes known as ‘enumeration’ in the structure of the Registry Adding new devices causes the system to check the existing configuration and determines what resources are available (I/O addresses,DMA channels..) so that the new device can be configured without clashing with an existing device -- The ‘plug and play’ feature (PNP)

32. Windows 2000 / XP Virtual Device Drivers: They are 32 bit, protected-mode drivers which manage a system resource (hardware device , software) so that more than one application can use the device at the same time Configuration Manager : Manages the ‘configuration’ process. It has a number of sub-components which are directed at ‘specifics’ e.g. buses, devices Ensures ‘no conflict’ of use of devices

33. Windows 2000 / XP Registry Configuration Manager Enumerator Arbitrator Device Driver Bus Bus Bus Device Device Device

34. Windows 2000 / XP PIC ISA Bus Plug and CDROM Root Play SCSI BIOS Display Controller DMA Parallel Hard Disk Personal Computer Memory Card International Association PCMCIA Bus Net Serial DMA Direct Memory Access SCSI Small computer system interface Keyboard Controller I/O

35. Windows 2000 and XP These have an Active Directory. This is the repository for all information related to the network - (users, groups, devices ….) The Lightweight Directory Access Protocol (LDAP) is also implemented in Novell Directory Services, Netscape Commerce Server, and the MS Exchange Server. Active Directory Services Interfaces (ADSI) enables 3rd party vendors to integrate with the current major directory services on the market. It’s getting larger and more powerful

36. Windows 2000 / XP Windows 2000 and XP are built around the concept of Domains An Active Directory is structured from Domains Trees Forests Organisational Units A ‘Domain’ contains containers and objects A security barrier handles access to resources ‘Policies’ determine which users can do what

37. Windows 2000 / XP The Registry is organised into ‘branch’ and ‘leaf’ structure (if you have used Explorer you will have seen this dependency and subdependency) The Branches are sections of the Registry (e.g. hardware registered on your PC) The Leaves contain data such as the hardware interrupt assigned to a multimedia device (recognition pattern)

38. Windows 2000 / XP The Organisation Units in the Registry are • Root Keys • Subkeys • Hives • Entries • A Root Key the major organisational unit in the Registry • HKEY_CLASSES_ROOT • HKEY_CURRENT_USER • HKEY_LOCAL_MACHINE • HKEY_CURRENT_USERHKEY_USERS

39. Windows 2000 / XP An example of the Units HKEY_LOCAL_MACHINE (Root Key) HARDWARE (Sub Key) DESCRIPTION SYSTEM CENTRAL PROCESSOR FLOATING POINT PROCESSOR SECURITY SOFTWARE Entries are contained at Root, Sub, and Hive level and contain the appropriate level details or data The Hardware ‘Hive’

40. Windows 2000 / XP And, a few words on Memory Paging Demand paging virtual memory system is used - data (and code) are moved in pages from physical memory to a temporary file on disk. When the information is required by a process, it is paged back into physical memory The Memory Pager maps virtual addresses from the process address space to physical pages in memory And a page ? - It’s a small block of logical memory and is either 2Kb or 4Kb.

41. A Few Extra Thoughts on XP It’s Physically ‘BIG’ It requires 2Gb of hard disk It takes about 75 minutes to install It is designed for ‘young’ high powered PC’s - less than 2 years old with a minimum of 128 Mb memory (256Mb ?) Very stable - (no more ‘blue screens of death ?) The taskbar and window borders are a ‘shimmering blue’ The icons are in 3D It looks suspiciously like an Apple Mac Lots of goodies - accommodates digital camera, MP3 music player, online chat, MSN Messenger, ..

42. A Few Thoughts on XP Copy protected - one copy per person (not per device owned by that person) It is suggested that XP should be installed on a new PC This saves upgrading and the cost of an XP Home Edition upgrade kit Can be upgraded from Windows 98, Me or 2000 - but NOT Windows95 Requires a minimum 300MHz processor (???)

43. Windows XP But apart from that : • It is very robust (no stalls) • It loads quickly (much more quickly than Windows 2000) - it loads in segment mode

44. A Competitor to Windows - Linux It is an operating system for servers It runs on all modern computer architectures It runs on clusters and Cray machines It is free of licence costs It appears to be a single, unifying platform with write-once, run anywhere capabilities It is not co-opted or owned by a single entity, corporation or government Support a number of graphical user interfaces Is available from several Web sites - Linux kernel, system utilities, applications and an installer It is known as ‘Open Source’

45. Recent Events with Linux • April, 2004 • Westpac and the National Australia Bank are seriously considering Open Source • The Commonwealth Bank will stay with Microsoft • The ANZ Bank ? Still Considering the Pros and Cons • Westpac and NAB are evaluating Linux on the desk top, and are also considering open source alternatives on their back-end operations • Possibly ATM and Teller environments • Possibly Internet banking platforms running on Linux • Telstra, NSW Roads Authority and NSW Department of Commerce which are also ‘interested parties’

46. Bank Compliance Projects up to 2007 • Money laundering legislation • New global accounting regulations • 2007 Basel 11 Accord deadline • Sarbanes-Oxley Act (US legislation) • Consumer concern regarding Internet Banking Security – do you remember the incresing in phising scams in 2003/2004 ? • Foreign exchange blowout ($A 360 million) – NAB • ‘Common’ Internet Banking System for Global Operations

47. Moving On We’ve spent some time on Windows 2000/XP Operating system facilities and components And on some of the hardware Hopefully you are more aware of the ‘insides’ of a PC - both hardware and software and of the interfaces used/required There are a few more items to conclude this overview

48. Factors Influencing Throughput • Basic machine cycle rate • Memory size • Instruction Cycle time • Input/Output device transfer speeds • Channel transfer rates • Chip stack size • Number of processors • Registers : Number, size, speeds

49. Registers These are special purpose (temporary) storage devices which are included in a computer to speed up processes Uses of Registers general purpose or scratch pad registers segment registers (code, data, stack, extra) offset registers - Instruction register - Stack - Base address - Memory address Flag register

50. CPU and I/O Devices ALU Control Unit Output Devices Input Devices Primary Storage Unit CPU