Questions tagged [memory-access]
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174 questions
1 vote
1 answer
92 views
Word size as a function of memory
In this lecture the professor says that $w$, the word size of a machine, and $n$, the amount of RAM in the machine, must be governed by the following relationship: $w \ge \log(n)$ But with $w$ bits we ...
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1 vote
1 answer
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Should "16MB × 64-bit DRAM" be interpreted as Mega-Bytes or Mega-Words?
In a DRAM architecture problem, I’m given: DRAM: 16MB × 64-bit DRAM chip: 512KB × 4-bit My professor repeatedly referred to these as Mega-Bytes and Kilo-Bytes, but ...
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1 answer
59 views
Can images be stored so that the maximum distance between neighboring pixels becomes less than D+1?
Suppose we have an image of size $D\times D$ (square). Can it be stored in memory such that the maximum distance between any two neighboring pixels is less than $D+1$? The neighboring pixels are ...
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Equation for access time confuses me
Why isn't the average access time of a cache (1-h)C and instead is hC? ,where h is the hit ratio and C is the access time of the cache? If the hit ratio is big ,then this means we have a cache hit ...
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1 vote
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Why did old RISC processors that required word-aligned loads and stores still use byte addressing?
I know most of those architectures added unaligned loads and stores later on, but when they first started, as far as I know, they were effectively word-aligned (faulting on any non-word aligned ...
- 11
3 votes
1 answer
1k views
How to allocate memory in NASM without C functions (x64)?
So I'm using NASM on linux and I was curious how this is done. All the info I can find online uses functions from C like malloc(). Can this be done purely with assembly code? Perhaps via a system call?...
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1 answer
277 views
RAM architecture vs. CPU architecture
I have learned that initially PCs had 8-bit memory architecture and that 1 byte (i.e. 8 bits) was the "basic" memory unit because 8 bits was exactly the memory space required to encode any ...
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1 answer
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Is there a delay between two commands to read data from RAM?
Everyone knows that the speed of the CPU is many times faster than the speed of RAM, whereas in this case the processor executes two read or write commands in memory running in a row? As I assume, due ...
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1 vote
1 answer
146 views
Byte addressing and alignment
With byte addressing, the CPU can access a single byte. But how does this access happen during alignment? As I understand it, if a CPU needs to read an unaligned byte, it reads the word starting from ...
- 11
2 votes
1 answer
235 views
Measuring Cache Access Time
I want to make a simple C program in order to measure L1, L2 and L3 latencies of my CPU. I know some info about them: ...
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1 answer
105 views
Same Address and Write signal for two block of RAM?
I don't know if I asked the question in correct way but I will try to explain what's the thing I am not getting. I am currently reading book titled "Code: The Hidden Language of Computer Hardware ...
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1 answer
104 views
How many bits do the pointers take?
So I am covering succinct trees, and in the lecture, it mentioned that "An n-node tree takes 2n pointers or 2n lg n bits (can be easily reduced to n lg n + O(n) bits). First, question is why ...
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2 answers
215 views
How does a CPU jump to a instruction thats no longer in ram?
Im designing my own CPU but I don't know how it jumps to an instruction that's no longer in ram. People have told me it puts the address in the SSD but for example, if the address were 3 in ram it ...
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3 answers
168 views
Is this how endianess work relative to memory?
So I've been trying to understand endianess for the past couple of days but I'm not sure if I'm overthinking this or not and I don't have anyone I can ask to confirm things. Here is how I look at ...
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1 answer
232 views
How can computers tell where the beginning and end of file/packet/frame headers are?
I'd like to know how a computer can determine the beginning and end of certain file components (attributes, headers, frame/packet/segment headers etc.) when these components can be omitted or added in ...
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