Questions tagged [clock-speed]

Anything related to clock signal frequency (a.k.a. clock speed) issues in digital systems.

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12
votes
5answers
5k views

“Overclocking” an AVR

In AVR datasheets under the Electrical Characteristics section you will typically find a graph like this (this one is from the ATMega328): I've seen designs that seem to "work" but operate outside ...
9
votes
1answer
7k views

Maximum clock frequency of microprocessors

Recently, I have heard that AMD has released the new Vishera series of FX processors which run at 5 GHZ. My question is whether there is any upper bound of clock rate of a processor? That is can we ...
15
votes
2answers
8k views

How can a CPU dynamically change its clock frequency?

My Intel CPU changes clock speed depending on the usage, but how does it decide what clock speed to run at? Is the clock speed determined by the OS software using an algorithm, or is it hardware based?...
8
votes
2answers
7k views

AVR interrupt service routine not executing as fast as expected (instruction overhead?)

I'm developing a small logic analyzer with 7 inputs. My target device is an ATmega168 with a 20MHz clock rate. To detect logic changes I use pin change interrupts. ...
5
votes
3answers
32k views

How to calculate the time of one single tick on microcontroller

I have been in Embedded system for 8 months. I have worked application part more compare with low level. I have basic questions on systems ticks, How to calculate the system tick of Timer, if I am ...
17
votes
7answers
34k views

How do I set the clock speed fuses on an ATtiny85 when using an Arduino as a programmer?

I'm following this tutorial, programming the ATtiny85 with an Arduino, using it to play some tones (through a piezo speaker). I'm struggling with getting the tones at the right pitch (I'm creating the ...
7
votes
4answers
628 views

Exotic semiconductors for fast digital ASIC

I am researching exotic semiconductors for a digital ASIC with a few million logic gates which should run as fast as possible within a $30 million budget. (Specifically, I need to do a single fully-...
6
votes
1answer
2k views

Is CPU/GPGPU heat dissipation quadratic in clock frequency?

In the following article on overclocking a Pentium from 1GHz to 5GHz using liquid nitrogen: The 5GHz Project, there is an assertion that "Heat dissipation rises exponentially during extreme ...
2
votes
3answers
2k views

Capacitive load - Matching Right Crystal and Caps for oscillator circuit - DS1302 RTC - cut and trim

CL = (C1 * C2) / (C1 + C2) + Cstray I have a 12.5pf crystal. DS1302 is happy with 6pf. what is trim capacitors to make him happy using 12.5pf? 12.5-6=6.5pf (6.5*6.5) / (6.5+6.5) + cstray= 3.25pf + ...
4
votes
3answers
777 views

ATmega - Why is the prescaler factory defaulted to 8?

Why do ATmega (e.g. 328P or 644P) have CKDIV8 (or CLKPS = 0011) factory programmed along with a default internal 8 MHz ...
1
vote
1answer
151 views

Error in dsPIC33 Family Reference Manual Oscillator?

I'm using an external 20MHz (categorized as high-speed or HS range) resonator and using PLL, but I'm not able to clock the device up anywhere near the max cpu speed advertised. How are you ever ...
1
vote
3answers
497 views

Reading data from digital pressure sensor (Pressure sensor SPD100GD)

We need to read the digital output from a Pressure sensor SPD100GD with an AVR micro (Atmega128). According to the datasheet we must estimate transmission speed. The datasheet is saying: The ...
0
votes
1answer
331 views

Zedboard clock cycles analysis

Based on the example in here, I tried a very similar example (but instead of multiplying two matrices I just multiply all the elements in a matrix by 2.0). However, when comparing the results of ...
0
votes
1answer
213 views

DDR2 data rate and data bus confusion

I am reading on DDR2 memory from past few days and have got confused with some of the terms involved. I am mainly confused from discrete memory (single DDR2 memory IC) rather than DIMM module which ...
0
votes
4answers
4k views

Why do we use negative edge trigger Flip Flop instead of positive edge triggered?

The glitches due to race condition can be avoided by using a negative-edge triggered flip-flop instead of the positive-edge-triggered flip-flop used. What does this mean? Source: http://www.zeepedia....