rehearsals on operating systems ram and traditional memory in a computer source: partly from per s....
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Rehearsals on Operating systems RAM and traditional memory in a
computer
Source: Partly from Per S. Laursen
EASJ - Partly from Per's slides 2
Internal memory
• What is internal memory anyway?• Just some chips that hold a certain
amount of data• In a modern computers the internal
memory typically consist of 2-16 Gigabyte
• What kind of data is stored? E.g. music on a mp3 file, that the CPU has to compute to turn it into music.
EASJ - Partly from Per's slides 3
Internal vs. external
• RAM as a kind of Internal storage has one big advantage: transfer of data between the CPU and RAM is pretty fast (several Gigabytes per. Seconds)
• Fast yes, - but compared to what?• But there are some major drawbacks:
– RAM is pretty expensive (compared to what?)– When power is turned off, all data disappear from the
internal storage– We therefore also need an external storage
EASJ - Partly from Per's slides 4
The external memory/storage
• Where does the data in the internal memory comes from? The data comes from the external storage
• What is the external storage? Overall, the same as the internal storage, ie a passive storage of data, BUT– Is usually much cheaper than RAM– Retains data when power is turned off
• Most common form of external storage in a modern PC is a hard drive
EASJ - Partly from Per's slides 5
A hard item…
• Moderne harddiske rummer typisk 200-1000 Gigabyte
• A hard disk drive includes a number of magnetic plates, where bits are stored, by magnetising a certain region of the plate
• Modern hard drives typically houses 300-4000 Gigabyte
EASJ - Partly from Per's slides 6
Harddrive vs. RAMHarddrive RAM
Typical amount in a PC
200-1000 GB 4-16 GB
Price per Gigabyte 0,50-1 kr. 50-200 kr.
Transfer rate 0,1-0,3 GB/sec 4-8 GB/sec
Saves data without electricity
Yes No
Technology Mechanical Electronically
EASJ - Partly from Per's slides 7
Harddrive vs. RAM
• In other words:• RAM:
– Very fast and stable, but– Very expensive, and does not save
data without power/electricity.
• Harddrive:– Very cheap and has a big capacity, and
saves data without power/electricity, but
– Very slowly, and is based on technic
Hard drive vs Solid State drive
• New: SSD (Solid State Drive).• Faster than Hard drive.• But more expensive
than Hard drive.
EASJ - Partly from Per's slides 9
Harddrive vs. SSDHarddrive SSD
Typical amount in a PC
200-1000 GB 64-256 GB
Price per Gigabyte 0,50-1 kr. 7-12 kr.
Transfer rate 0,1-0,3 GB/sec 4,8 - 6 GB/sec(SATA 3/6)
Saves data without electricity
Yes Yes
Technology Mechanical Electronically
EASJ - Partly from Per's slides 10
Is a computer ”born” with an Operating system (OS)?
• BIOS handles very basic actions as a keystroke, and the drawing of letters on the screen
• When a computer starts, the BIOS is set to start
• The main task of the BIOS is starting the right operating system
• BIOS is a chip in your PC
EASJ - Partly from Per's slides 11
Administration of programs• Last time we discussed what it means, when the virtual memory
is larger than the RAM.• When we start a program, it will be copied from the external
memory/storage to the internal storage(RAM), and set in motion
Operating system
Program
Program
Program
The internal storage (RAM)
EASJ - Partly from Per's slides 12
Administration of programs
• The operating system must "find room" for the program in the internal storage - what if there is no more space?
Internal storage
Program
Program
Program Program
Program Program
Program Program Program
Program
What now?
EASJ - Partly from Per's slides 13
Administration of programs• The operating system can use some of the external storage
(hard drive), as an "emergency extension" to the internal storage
Internal storage
Program
Program
Program Program
Program Program
Program Program Program
Additional(temporarily)
internal storage
Program
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