# 3.2 Review question: memory management  (Page 3/4)

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b.      2. Show the binary tree representation following Return B.

## Consider a buddy system in which a particular block under the current allocation has an address of 011011110000.

a.       If the block is of size 4, what is the binary address of its buddy?

If the block is of size 4, the binary address of its buddy is 011011110100

b.      2. If the block is of size 16, what is the binary address of its buddy?

If the block is of size 16, the binary address of its buddy is 011011100000.

## Consider a simple paging system with the following parameters: 232 bytes of physical memory; page size of 210 bytes; 216 pages of logical address space.

a.       How many bits are in a logical address?

The number of bytes in the logical address space is (216 pages) * (210 bytes/page) = 226 bytes. Therefore, 26 bits are required for the logical address.

b.      How many bytes in a frame?

A frame is the same size as a page, 210 bytes.

c.       How many bits in the physical address specify the frame?

The number of frames in main memory is (232 bytes of main memory)/(210 bytes/frame) = 222 frames. So 22 bits is needed to specify the frame.

d.      How many entries in the page table?

There is one entry for each page in the logical address space. Therefore there are 216 entries.

e.       How many bits in each page table entry? Assume each page table entry includes a valid/invalid bit.

In addition to the valid/invalid bit, 22 bits are needed to specify the frame location in main memory, for a total of 23 bits.

## Consider a paged virtual memory system with 32-bit virtual addresses and 1kb pages. each page table entry requires 32 bits. it is desired to limit the page table size to one page.

a.       How many levels of page tables are required?

Virtual memory can hold (232 bytes of main memory)/( 210 bytes/page) = 222 pages, so 22 bits are needed to specify a page in virtual memory. Each page table contains (210 bytes per page table)/(4 bytes/entry) = 28 entries. Thus, each page table can handle 8 of the required 22 bits. Therefore, 3 levels of page tables are needed.

b.      What is the size of the page table at each level? Hint: One page table size is smaller.

Tables at two of the levels have 28 entries; tables at one level have 26 entries. (8 + 8 + 6 = 22).

c.       The smaller page size could be used at the top level or the bottom level of the page table hierarchy. Which strategy consumes the least number of pages?

Less space is consumed if the top level has 26 entries. In that case, the second level has 26 pages with 28 entries each, and the bottom level has 214 pages with 28 entries each, for a total of 1 + 26 + 214 pages = 16,449 pages. If the middle level has 26 entries, then the number of pages is 1 + 28 + 214 pages = 16,641 pages. If the bottom level has 26 entries, then the number of tables is 1 + 28 + 216 pages = 65,973 pages.

## A process has four page frames allocated to it. (all the following numbers are decimal, and everything is numbered starting from zero.) the time of the last loading of a page into each page frame, the last access to the page in each page frame, the virtual page number in each page frame, and the referenced (r) and modified (m) bits for each page frame are as shown (the times are in clock ticks from the process start at time 0 to the event -- not the number o fticks since the event to the present).

Virtual Page Number          Page Frame      Time Loaded    Time Referenced          R Bit    M Bit

do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
Do somebody tell me a best nano engineering book for beginners?
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
how did you get the value of 2000N.What calculations are needed to arrive at it
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