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80 votes
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Why is the Nintendo Entertainment System (NES) referred to as an 8-bit system, rather than a 1-byte system?

"Back in the day" computers were defined more by their word size, for example the PDP-8 had 12-bit words composed of two 6-bit "bytes". A "nibble" was half a byte, or 3 bits in this case (and here the ...
C8H10N4O2's user avatar
  • 746
44 votes

Why is the Nintendo Entertainment System (NES) referred to as an 8-bit system, rather than a 1-byte system?

A) Historically, machines have been characterized by number of bits per 'machine word'. Why should NES be handled differently? B) Calling it a 'byte' is not as clear since historically a 'byte' has ...
PMar's user avatar
  • 311
8 votes
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Why do we still use a Von Neumann Architecture in modern computers?

So why do we still use this architecture in the majority of modern computing? The assumption itself, first clause: Modern Computer <= Von Neumann Firstly, do note that the Von Neumann ...
Tobia Tesan's user avatar
6 votes
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Why RAID 2 would ever be used instead of RAID 3?

RAID 2 doesn't use parity: it uses a Hamming code. This allows error correction as well as error detection. Remember that a parity bit is just a bit that tells you whether the sum of the other bits is ...
David Richerby's user avatar
6 votes
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Representation of used space and free space in hard drives

Free space is a concept at the level of the filesystem, which is part of the operating system. It is up to the filesystem to determine what space is free, and how to exploit it. Data is stored on the ...
Yuval Filmus's user avatar
6 votes
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How does software prefetching work with in order processors?

"In-order" processors only issue instructions in order. Completion is out-of-order even on most processors that are called "in-order". "in-order" just means: if the ...
Wandering Logic's user avatar
5 votes

How does hardware interrupt work on a physical layer

The CPU has specific pins on the outside to detect hardware interrupts. Take for instance the 6502 used in the Apple II and c64 it has two interrupt pins: IRQ on pin 4 and (can be ignored) NMI on ...
Johan's user avatar
  • 1,080
5 votes
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Variable size and CPU performance

Would it make any difference performance-wise to only use the largest variable size on the platform and use business logic to enforce reasonableness in the values being processed and stored? Yes, it ...
manlio's user avatar
  • 2,062
5 votes

Why is 2^32 in a 32-bit system = 4GiB and not 4Gib?

"32-bit" describes the size of many of the units of data that the processor can use. In this context, it refers to the size of memory addresses. A 32-bit address can address $2^{32}$ distinct objects; ...
Curtis F's user avatar
  • 1,043
4 votes

What's the difference between Memory Byte (Mb) and Mega Byte (mb)

Ok - there's a lot of muddle here! "Memory Byte" isn't a term at all. Nor is "mb" - that would mean "milli-bit", which isn't really a thing! MB means Megabyte - which means either 1,000,000 bytes, ...
SusanW's user avatar
  • 143
4 votes

Who converts binary/machine code to electrical signals and how?

The question is asking there must be something between the machine code and the electric signal in the computer. For example, a program written in C++ is compiled into machine code first, then it is ...
MartinLA2020's user avatar
4 votes

Who converts binary/machine code to electrical signals and how?

The CPU What is important to understand is that the CPU comes with a predefined instruction set that it can handle. For example, x86-64 CPUs have a defined set of instructions that they can operate on....
user123's user avatar
  • 1,112
4 votes
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Does word addressable memory have more bytes than byte addressable memory?

If you had a byte addressable architecture where pointers have a fixed size, and every or almost every bit pattern is a valid pointer to a distinct byte address, and a word addressable architecture ...
gnasher729's user avatar
  • 30.4k
4 votes

Why is data fragmentation not possible on main memory (RAM)?

According to https://lwn.net/Articles/211505/, what you imagine should be done by the OS, is already done: Since Linux is a virtual memory system, fragmentation normally is not a problem; ...
Toni's user avatar
  • 41
4 votes

Representation of used space and free space in hard drives

The operating system knows what parts of memory are free and what parts are in use by keeping track of all allocations to processes; anything that isn't allocated is free. Disks are exactly the same: ...
David Richerby's user avatar
4 votes

Is CPU Registers part of Primary Memory?

CPU registers are often counted as part of primary memory (since they are directly accessed by the CPU - see Wikipedia) and are often volatile, so it seems likely that the expected answer is (1). ...
gandalf61's user avatar
  • 1,589
4 votes

How does a dual core microprocessors run so many programs?

It's great that you're curious. A simplified explanation follows with a few links to delve into: All of the programs running in parallel is actually an illusion that is created by the OS. Even if we ...
ss09's user avatar
  • 96
4 votes
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How LRU is used without special hardware?

The Linux kernel uses a (very rough) approximation of LRU, which is the reason why you find mention of LRU, even though it is not the true LRU algorithm. Here is a description taken from the source: ...
Vincenzo's user avatar
  • 3,302
3 votes

How does a computer determine the data type of a byte?

Datatypes are not a hardware feature. The CPU knows a couple (well, a lot) of different commands. Those are called the instruction set of a CPU. One of the best known ones is the x86 instruction set. ...
Martin Thoma's user avatar
  • 2,360
3 votes

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

How is it possible that tha same ram, i.e given the ram size is 4 GB, would contain different number of bytes depending on byte/ word addressable memory? It isn't. a 4GB amount of ram would either ...
Tom van der Zanden's user avatar
3 votes

how one memory can be accessed simultaneously in instruction fetch and data read?

Modern CPUs usually feature separate instruction and data caches, so effectively, even if from a software PoV, everything is coming from a single memory space, there are physically separate busses and ...
Grabul's user avatar
  • 1,870
3 votes

How many bytes of memory is used just to "acknowledge" that a certain file is a .jpg?

Depends on how accurately you want it to be. If you trust the extension then all you need is the 4 last characters in the file name (32 bits) If you trust the magic header number then you need to ...
ratchet freak's user avatar
3 votes
Accepted

How many bytes of memory is used just to "acknowledge" that a certain file is a .jpg?

Zero. A file type doesn't need to be “acknowledged”. Imagine a photo of a tree. How much surface on the photo is needed to acknowledge where the photo was taken? Zero. The photo doesn't need to ...
Gilles 'SO- stop being evil''s user avatar
3 votes
Accepted

What the heck is a memory channel "CS bus"?

I think it is the "Chip Select" part which is mentioned at slide 26. It probably selects whether to use the chip on the front or in the back.
chi's user avatar
  • 14.6k
3 votes

Difference between RAM and buffer

Buffer is a concept. It's a structure used to hold data to keep it "closer" while you're processing it. Like buffering a YouTube video. Many types of memories are used as buffers. RAM is certainly ...
Jimmy Potter's user avatar
3 votes
Accepted

Slowdown when accessing data at page boundaries?

Go to Agner manuals page and download them all, you will find tons of interesting info there. In particular, microarchitecture.pdf says There is a false dependence between memory addresses with ...
Bulat's user avatar
  • 1,873
3 votes
Accepted

Is it reasonable to model row buffers in DRAM corresponding to the same bank ID as one big row buffer?

You can look at how one of the existing DRAM simulators work. Consider, for example, Ramulator, which is a popular academic DRAM simulator. Ramulator Models main memory as a tree of nodes, where the ...
Hadi Brais's user avatar
3 votes

How does virtual memory work when it need to save data in physical memory into disk?

There are a few options: if a page is in memory then it cannot be on disk as well, As such there is no duplication and the issue doesn't exist. there is more than just the MMU's pagetable to hold ...
ratchet freak's user avatar

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