Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [cpu]

The CPU, the Central Processing Unit, is known as the heart of the computer. It is responsible for carrying out the instructions of a computer program by performing the basic arithmetic, logical, control, and input/output (I/O) operations specified by the instructions.

A typical CPU consists of:

  • an ALU, or Arithmetic and Logic Unit, which handles addition, subtraction, multiplication, division, and logic operations
  • a register file
  • a control unit, which fetches, decodes, and executes instructions

It is usually connected to memory containing both program and data, and control ports for memory and other peripheral parts.

See also:

605 questions
119
votes
7 answers

What limits CPU speed?

I've recently talked with a friend about LaTeX compilation. LaTeX can use only one core to compile. So for the speed of LaTeX compiliation, the clock speed of the CPU is most important (see Tips for choosing hardware for best LaTeX compile…
Martin Thoma
  • 1,327
  • 2
  • 9
  • 9
64
votes
10 answers

Why is RAM not put on the CPU chip?

Modern CPUs are very fast compared to all things external, including memory (RAM). It is understandable, since CPU clock frequency has reached a point where it takes several clock ticks for an electric signal simply to run from from the CPU through…
Lesser Hedgehog
  • 751
  • 1
  • 6
  • 6
62
votes
5 answers

How can an FPGA outperform a CPU?

I hear of people using FPGAs to improve performance of systems that do things like bit-coin mining, electronic trading, and protein folding. How can an FPGA compete with a CPU on performance when the CPU is typically running at least an order of…
David Gardner
  • 1,583
  • 1
  • 13
  • 15
59
votes
5 answers

Why does more transistors = more processing power?

According to Wikipedia, processing power is strongly linked with Moore's law: http://en.wikipedia.org/wiki/Moore's_law The number of transistors that can be placed inexpensively on an integrated circuit has doubled approximately every two…
Oli
  • 693
  • 1
  • 5
  • 7
59
votes
10 answers

Why is there no `nand` instruction in modern CPUs?

Why did x86 designers (or other CPU architectures as well) decide not to include it? It is a logic gate that can be used to build other logic gates, thus it is fast as a single instruction. Rather than chaining not and and instructions (both are…
Amumu
  • 895
  • 1
  • 6
  • 7
54
votes
7 answers

Why don't we make CPUs with 1000s of layers to make use of space in the third dimension?

I am wondering why don't we make processors such as CPUs with 1000s of stacked layers to make use of space in the third dimension now that we have three-dimensional transistors. To be clear I'm referencing making something of a rectangular-prism…
Ethan
  • 679
  • 1
  • 7
  • 9
50
votes
5 answers

How can a CPU deliver more than one instruction per cycle?

Wikipedia's Instructions per second page says that an i7 3630QM deliver ~110,000 MIPS at a frequency of 3.2 GHz; it would be (110/3.2 instructions) / 4 core = ~8.6 instructions per cycle per core?! How can a single core deliver more than one…
davide
  • 603
  • 1
  • 5
  • 5
45
votes
5 answers

How can cache be that fast?

Here is a screenshot of a cache benchmark: In the benchmark the L1 cache read speed is about 186 GB/s, with the latency being about 3-4 clock cycles. How is such a speed even achieved? Consider the memory here: the theoretical maximum speed is 665…
Knight
  • 613
  • 1
  • 5
  • 8
44
votes
2 answers

Why do CPUs need so much current?

I know that a simple CPU (like Intel or AMD) can consume 45-140 W and that many CPUs operate at 1.2 V, 1.25 V, etc. So, assuming a CPU operating at 1.25 V and having TDP of 80 W... it uses 64 Amps (a lot of amps). Why does a CPU need more than 1 A…
Leonardo Bosquett
  • 599
  • 1
  • 4
  • 5
39
votes
5 answers

When Intel / AMD choose their Nanometer Processes, why were the specific numbers, 5, 7, 10, 14, 22, 32, 45, etc chosen?

When looking at the roadmaps for the CPU manufacturing process https://wccftech.com/intel-expects-launch-10nm-2017/ 10 µm – 1971 6 µm – 1974 3 µm – 1977 1.5 µm – 1981 1 µm – 1984 800 nm – 1987 600 nm – 1990 350 nm – 1993 250 nm – 1996 180 nm –…
Anon
  • 525
  • 1
  • 4
  • 6
39
votes
6 answers

Why does Intel's Haswell chip allow floating point multiplication to be twice as fast as addition?

I was reading this very interesting question on Stack Overflow: Is integer multiplication really done at the same speed as addition on a modern CPU? One of the comments said: "It's worth nothing that on Haswell, the FP multiply throughput is double…
Nike Dattani
  • 547
  • 7
  • 22
31
votes
3 answers

Can you make a CPU out of electronic components drawn by hand on paper?

I explored a lot of literature about paper-based electronics recently, and one particular paper caught my interest: “Handwritten Oxide Electronics on Paper” (DOI: 10.1002/admt.201700009) by Elvira Fortunato et al. It explains a method to make…
Zoé Martin
  • 491
  • 4
  • 9
31
votes
5 answers

Why don't we see faster 7400 series chips?

The 74HC series can do something like 20MHz while 74AUC can do something like maybe 600MHz. What I'm wondering is what sets these limitations. Why can't 74HC do more than 16-20MHz while 74AUC can and why can't the latter do even more? In the latter…
Anthony
  • 733
  • 6
  • 20
30
votes
7 answers

Is transistor the only electronic component on a CPU?

I have been reading about CPUs recently and came to know that all logical blocks and memory on CPU can be made out of transistors. So is it the only electronic component on CPU? Edit (Made after first two answers): But the making of CPU only talks…
Darth Pingu
  • 471
  • 1
  • 4
  • 7
29
votes
7 answers

Why aren't CPUs cooled from below as well as above?

The transistory bits of an integrated circuit are approximately in the centre of the (plastic or ceramic) package. They sometimes get hot, and we cool them by affixing a heat sink to one side. Sometimes we just blow air over them with a fan. Some…
Paul Uszak
  • 7,327
  • 5
  • 37
  • 69
1
2 3
…
40 41