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3 views

Does word addressable memory has more bytes than byte addressable memory?

Well, my question - if word addressable has more bytes than byte addressable - is derived from the fact that in word addressable memory each address adresses a word and in byte addressable memory each ...
2
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1answer
27 views

Why not space out memory allocations?

In ext4 file system, the files are spaced out as far apart as reasonably possible to allow for efficient reallocation. Why do we not do this in memory? Why not allocate one memory as page 20, and the ...
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0answers
21 views

How are LRU and Clock algorithm different?

I am modeling the Gclock-pro buffer replacement algorithm in Linux kernel. Because there are many existing modeling works on LRU, I am considering adopting LRU model to roughly describe Gclock-pro, ...
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0answers
48 views

How do stack-based cache algorithms avoid Belady's anomaly?

I was going through page replacement algorithms from Galvin's Operating System book. I encountered this line about LRU: A stack algorithm is one in which the pages kept in memory for a frame set ...
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0answers
18 views

When was manual dynamic memory managment introduced?

Original Fortran only had static memory. Algol introduced stack allocation. Lisp had Garbage Collection. But when where manual dynamic memory management such as in C introduced. In C memory can be ...
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2answers
63 views

Pros and Cons of Average Memory Access Time When Increasing Cache Block Size

Assuming we have a single-level (L1) cache and main memory, what are some of the advantages and disadvantages of having a larger cache block size (considering average memory access time). The only ...
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1answer
31 views

Not sure about a part of an answer - page table size question

Below is a question and answer that I'm reviewing. I understand most of it but I'm not clear where the 8 bits for the PTE size came from in this part... ...
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1answer
33 views

Effect of Copy-On-Write on 2 processes sharing address space

I am studying operating systems and was going through Copy On Write mechanism. From Wiki: When one process modifies the memory, the operating system's kernel intercepts the operation and copies ...
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0answers
92 views

How to calculate virtual address space from page size, virtual address size and page table entry size?

I try to solve an exercise, unfortunately without any success yet. From the following given information, the virtual address space should be calculated: Page size is 16 KB Logical address size is ...
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1answer
30 views

Address space definition

I'm learning by my self about OS theory and I have some troubles to understand what is a process address space. So far, I came across two definitions of what a process address space is: 1 - The set ...
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1answer
55 views

What are logical addresses and where do they actually reside?

While studying about memory management, paging and segmentation there is a lot of usage of phrases like CPU generates logical addresses and ...
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1answer
34 views

Virtual address lookup without using all the space to store the physical addresses [closed]

How is a virtual address mapped to a physical address? The most logical solution I, with my meager knowledge, can think of would be to actually store the physical address. The problem with the above ...
0
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2answers
29 views

Increasing Cache Line and Programs with bad Spatial Locality

I'm reading on caches and I'm feeling a bit lost with spatial locality. From my understanding, increasing the cache line with a program that has high spatial locality reduces the miss rate. But for ...
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0answers
21 views

simple fixed block size allocator and block header

Lets say I want to implement my simple version of free/malloc Lets assume I got a huge chunk of memory where I manage my free/malloc there . and also I can only allocate fixed block size on each ...
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1answer
30 views

Does the memory get unallocated when program exits?

I have been trying to manipulate pointers just for the sake of studying. I have had some problems with some programs I wrote where I had memory leak. Does this memory stay allocated even when the ...
2
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1answer
54 views

Optimal Page Replacement Algorithm - If more than one frame will not be used again, which one gets replaced?

This may not make a difference in the end, but not knowing is driving me insane. When using the Optimal algorithm for page replacement, if you need to put something new into a frame and you have more ...
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7answers
5k views

Is a computer without RAM, but with a disk, equivalent to one with RAM?

Memory is used for many things, as I understand. It serves as a disk-cache, and contains the programs' instructions, and their stack & heap. Here's a thought experiment. If one doesn't care about ...
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1answer
22 views

Mapping several memories to one address space

I am trying to understand deeply how memories work in computers, and I faced the next difficulty. Let's say we have a device with two memory chips but only one address space (for example, 0x00000000 ...
3
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2answers
55 views

Why is word-addressable the exception, not the rule?

As stated on Wikipedia: Most modern computers are byte-addressable instead of word-addressable. Why is this case? Since the CPU processes words (of predominantly 64 bits or 8 bytes) now, wouldn'...
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1answer
58 views

Number of addresses in a memory region

So I am looking at some Operating Systems exercises and we have A swapping system eliminates holes by compaction. Assuming a random distribution of many holes and many data segments ...
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2answers
64 views

What's the difference between clock replacement & LRU replacement?

As title. When we want to request following page numbers 2,4,4,2,5,2,1,1,3,1, is clock replacement better? What are the advantages and disadvantages of them? Thanks~
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1answer
53 views

Why is the processes address space a continuous block in RAM?

I need some clarification regarding how the process address space is organized in memory. I went through basic concepts of virtual memory and adress translation and according to the size of the page, ...
3
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0answers
70 views

Swap and Memory: Stack, Heap, or Both?

I understand what stack and heap refer to. However, I struggle with understanding exactly swap can do. For example, let's take Linux as the OS. I connect another hard disk to my machine, and I make ...
2
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1answer
64 views

Is the memory usage of total languages deterministic?

I'm interested in the memory usage of various programming languages when implemented on actual hardware. I believe that a Turing-complete programming language has, in general, unknowable memory usage ...
2
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2answers
337 views

Virtual Address and Physical Address Space

A machine has 48-bit virtual addresses and 32-bit physical addresses. Pages are 8K. How many entries are needed for a conventional page table ? The answer is 2^35 entries Why not (2^32) / (2^13) = ...
3
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1answer
66 views

Combining adjacent memory blocks

This is a conceptual issue that I am having in designing an algorithm for a memory allocator that works in conjunction with memory pooling. Free blocks are put on one of several free lists within the ...
3
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1answer
63 views

How can I calculate the effective bandwidth of a memory system?

I am currently doing my homework for my Computer Architecture class. One of the questions asks: A computer has a 64-bit data bus and 64-bit-wide memory blocks. The memory devices have an access ...
4
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0answers
32 views

How did MacLisp's garbage collector “run in the register set”?

Olin Shivers, ‘History of T’: Maclisp on the [PDP]-10 had used a mark&sweep GC (one version of which famously "ran in the register set," though that is another story) This implies, in my ...
3
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1answer
93 views

How ram is divided

when I write a program, in a Von Neumann architecture, how the ram will be divided to receive data and instructions? For example if I have 1 MB of ram, the addresses from 0 to 499.999 for data and ...
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2answers
134 views

What is the file system of ram?

As much I know about a memory and storing data there would always be a managing type feature in every memory which manages all the data and its location. So, what is the file system of a RAM. I also ...
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2answers
112 views

In a $k$-way set associative cache,main memory block mapping in range?

In a $k$-way set associative cache, the cache is divided into $v$ sets, each of which consists of $k$ lines. The lines of a set are placed in sequence one after another. The lines in set $s$ are ...
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3answers
75 views

How are variables accessed in the correct order from the stack?

I'm learning about the stack but one thing I am unable to understand is how variables can be accessed in the correct order. So if I had a basic program calculating the sum of some user entered values ...
1
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1answer
40 views

What does x-bit binary number means?

What does x-bit binary number mean? for example: if x = 8 is 8-bit means: any number consists of 8 bits, like : 10101110 or it has another meaning??
2
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1answer
138 views

Best Fit Memory Allocation Algorithm Statistical Analysis

I've been reading book on Operating System, in which author writes : Somewhat surprisingly, it(Best fit) also results in more wasted memory than first fit or next fit because it tends to fill up ...
2
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1answer
29 views

Operating Systems TestAndSet instruction

I was reading operating systems concurrency control topics where I came across TestAndSet() intruction. I first referred this book. But it has got very less ...
2
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2answers
2k views

Is page size always equal to frame size?

I'm learning about paging. My book says that the logical addresses generated by the CPU are in the form |p|d|(page number, page offset) and the physical addresses ...
4
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0answers
55 views

How are weak references in a reference counted system implemented?

When reference counting is used for automatic memory management (e.g. Objective C or Swift), it is well know that “loops” give problems. E.g. ...
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2answers
359 views

How to calculate the size of a page in a two level paging CPU?

I am having difficulties with understanding the concept of paging. As a result I've got no idea how I can solve the following exercise - I'm lacking one more equation to solve it. I've read a lot ...
2
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0answers
59 views

How does the Spark M7 “Concurrent Fine-grain Memory Migration” benefit a garbage collector?

Sun has been making a lot of noise about the Spark M7 and its inbuilt support for the java garbage collector. However there seem to be very little easy to find information about it. Please can ...
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4answers
324 views

Can only information(data) be stored in ram?

Basic question, but is only information/ data stored in ram? Are computer files such as a word file considered information/ data? This is one of the questions in a summer assignment for ap computer ...
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1answer
81 views

How does the operating system set up memory boundaries? [closed]

Is there a hardware interrupt that is pre-configured by the OS or something? Try to keep the answer on the scale of a register or so. Are some special preparatory signals sent across the bridges ...
7
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1answer
79 views

Page management in OS kernels

I looked at some old OS theory books of mine and noticed that one glaring omission in all of these OS books is how to actually keep track of physical pages that are free (i.e. algorithms for actually ...
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3answers
171 views

Data types for storing arbitrarily much information

I've heard that YouTube had a problem with the view count on Gangnam style since the number of views exceeded the variable byte size. What's the problem with creating really large variables? Why ...
1
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1answer
635 views

How do binary trees use memory to store its data?

So I know that arrays use a block on contiguous memory addresses to store data to memory, and lists (not linked lists) make use of static arrays and when data is appended to the list, if there is no ...
0
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0answers
34 views

Is this cache entry a hit or a miss? [duplicate]

The Problem: A CPU produces the following sequence of read addresses in hex. Suppose the cache is empty to begin with and assuming an LRU replacement, determine whether each address produces a hit or ...
0
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0answers
161 views

What happens if the associativity level is greater than the cache size?

I am working on a computer organization caching problem The Problem: What happens if the associativity level is greater than the cache size? I know that associativity level is how many blocks are ...
2
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0answers
51 views

When there's no memory, should malloc or read/write fail?

To my surprise, I recently found out that Windows would fail a large memory allocation even if little of said memory is to actually be used, e.g. even if you don't want the swap, you better not ...
2
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2answers
131 views

where is all deleted data will go from memory system/internet? [closed]

where is all deleted data will go from a memory system ? if it is not deleting actually where it storing ? i am always wonder about this when we are sending something to a memory system it takes ...
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votes
1answer
2k views

Size of address spaces (logical and physical)

Suppose a system in which addresses (physical and logical) occupy 32 bits, page size is 1024 bytes (210), and physical memory is of size 32MB. How many frames are in physical memory? Is the logical ...
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0answers
107 views

Clock variant of the Second-Chance page-replacement Algorithm vs. standard Second-Chance Algorithm

A sample question for my upcoming Operating Systems exam is: Under which circumstances would the clock variant [of the second-chance algorithm] be preferred over the standard second-chance ...