What is Refresh: Definition and 26 Discussions

Memory refresh is the process of periodically reading information from an area of computer memory and immediately rewriting the read information to the same area without modification, for the purpose of preserving the information. Memory refresh is a background maintenance process required during the operation of semiconductor dynamic random-access memory (DRAM), the most widely used type of computer memory, and in fact is the defining characteristic of this class of memory.In a DRAM chip, each bit of memory data is stored as the presence or absence of an electric charge on a small capacitor on the chip. As time passes, the charges in the memory cells leak away, so without being refreshed the stored data would eventually be lost. To prevent this, external circuitry periodically reads each cell and rewrites it, restoring the charge on the capacitor to its original level. Each memory refresh cycle refreshes a succeeding area of memory cells, thus repeatedly refreshing all the cells in a consecutive cycle. This process is conducted automatically in the background by the memory circuitry and is transparent to the user. While a refresh cycle is occurring the memory is not available for normal read and write operations, but in modern memory this "overhead" time is not large enough to significantly slow down memory operation.
Electronic memory that does not require refreshing is available, called static random-access memory (SRAM). SRAM circuits require more area on a chip, because an SRAM memory cell requires four to six transistors, compared to a single transistor and a capacitor for DRAM. As a result, data density is much lower in SRAM chips than in DRAM, and SRAM has higher price per bit. Therefore, DRAM is used for the main memory in computers, video game consoles, graphics cards and applications requiring large capacities and low cost. The need for memory refresh makes DRAM timing and circuits significantly more complicated than SRAM circuits, but the density and cost advantages of DRAM justify this complexity.

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  1. A

    Good Book(s) to Refresh Physics I & II?

    I have a handful of eBooks, but trying to figure out what one(s) would be best to refresh myself on Physics I and II. I see Fundamentals of Physics by Halliday & Resnick in my collection, and from what I remember, it's one of the better ones, right? Also, assuming that's the case, it looks...
  2. S

    Embedded video "can't play here" --> Refreshing may help

    Just noticed that sometimes, if a youtube video embedded in a post is marked "This video can't be viewed here..." , it may get enabled if you refresh the page.
  3. Weightlifting

    Intro Physics Starting fresh, but where to start?

    Hello everyone! I'm new to this forum, and I've tried looking at all the conventions on the forum, but if anything I say is out of line, please speak up! With that out of the way, I've added some of my background in physics in the spoiler, with the main questions below that. Looking back at...
  4. J

    Subtracting object MOI from assembly to get other parts MOI?

    Homework Statement It's been ages since I have done Moments of Inertia of complex objects! :( Can anyone help?? Say you have an assembly like an airplane and you want to just get the moment of inertia(MOI) of the tail section and you are given the Mass of whole plane,mass of tail section...
  5. T

    Classical A General Physics refresher book?

    Hi everyone, I just created this account because it was actually the first time I wanted to ask a question myself, but this forum has helped me a lot in the past with my Physics and Maths related courses. So thank you for that. Going back to the topic...Now that I've completed some of the...
  6. AirmanX

    Programs Returning to Physics After 4 Years: Should I Refresh or Push On?

    Perhaps this isn’t the place to ask, but I was just looking to hear opinions from some people on here about my situation. I’ve been out of school for 4 years now, having left to enlist with the Air Force. While in school I was majoring in Physics/Mathematics. I was a B student in Physics 1, 2...
  7. A

    Unknown light-based Phenomenon

    Can you help me figure out how this light-based phenomenon works? Please explain with an intuitive answer using the simplest principles possible. Note how the location and width of the dark horizontal bands is constant with respect to the edge of the video frame. The LED light looks normal...
  8. N

    Solving for n: power and log rules refresh

    Homework Statement A computer can perform 1010 ops/s. Assume 1 op per 1 input. Given the following algorithmic complexities how many inputs can be performed in an hour. n2 n3 100n2 n log n 2n 22n Homework EquationsThe Attempt at a Solution [/B] C = 1·1010 ops/s · 3.6·102 s/hr C = 3.6·1012...
  9. D

    30FPS displayed on a 200Hz monitor

    Hello! I have a PAL TV, and that means it is best for footage of 25fps and 50fps The TV's refresh rate is 200Hz Well, my questions are: What happens if I play an NTSC file on the TV? (≈30fps), since it doesn't go well with 200Hz much (isn't a multiple)... I thought about how would the TV...
  10. P

    Gravity Field Measurment / Refresh Rate of Sensors

    Hi Reading another post about the inverse square law by trewsx7 on this forum, I had the idea that maybe the gravity field isn't constant at some parts. Imaging a 2-dimensional gravity field produced by a source. Considering ∏, there might be a repeating infinitesimal patterns on ∏ where...
  11. B

    How to make the clock refresh instead of it repeating every second

    I did the following program #include<stdio.h> #include <stdlib.h> #include <time.h> int main (void) { int sec,min,h; printf("please enter the the time in the following format hh:mm:ss :"); scanf("%d:%d:%d",&h,&min,&sec); for ( ; ; ) { sleep(1);// a delay function which delays by a second...
  12. L

    What are some online resources for learning 11th grade physics?

    Canadian physics standards may be different then that of US Standards. I am middle aged but wanted to try for the electrician apprentice program offered by the local technical collages. In order to be a apprentice, 11th grade physics and 11th grade math are pre requirements and I will be...
  13. C

    I want to refresh my Precalculus using James Stewart's book but I got a question

    Hello people, I want to refresh my Precalculus using James Stewart's book but I got a question about the exercises. I have bought the book and I will self study it. Do you think I should do all the exercises at the end of the chapters? How do you self study a book? I am waiting for your...
  14. M

    What happens to the probability if a case is revealed to be a winning scenario?

    Firstly, I would like to say that I am an applied physics major, so my knowledge on probability not relating to statistical mechanics is probably pretty shaky (and, to be completely honest, my knowledge of statistical mechanics may be equally as shaky). That being said, this question may be...
  15. C

    Refresh my calculus for general solution of Aexp(-ikx)

    Homework Statement If \psi(x) = Ae-ikx then the general solution \psi(x) = Asin(kx) + Bsin(kx) May I know if this is ODE? or? sorry, I need a refresher on my calculus. Homework Equations The Attempt at a Solution Homework Statement Homework Equations The Attempt at a Solution
  16. B

    Medical Does the human eye have a refresh rate ?

    Does the human eye have a "refresh rate"? This question probably seems ridiculous, but I have no background in physiology and I cannot find anything discussing it online or in my roommate's physiology textbook. I was wondering if anyone here knows whether the eye and brain processes...
  17. P

    Unwanted Computer Usage: 50Hz Refresh Rate Issue on My Lab Computer - Need Help!

    my computer in the lab has been used without my permission by a labmate He told people that he knew about computer OS, he partitioned the computer discs into many rooms. There is a drive room for my Windows XP 2003 Service Park 2. He installed some OS I don't know what to call on the other free...
  18. N

    MATLAB Need help with Matlab GUI – how to refresh/ redraw?

    Hello: Could you possibly help me. I am writing a fairly simple GUI. The callback for “Start” button does the following: 1) Clears the current plot displayed in an Axis object 2) Calculates data for a new plot 3) Plots the new plot in Axes object from 1) I need 1) to take place...
  19. rocomath

    Refresh my memory , Inverse Trig

    Refresh my memory please, Inverse Trig x=\sin^{-1}\left(-\frac{\sqrt{2}}{2}\right) Inverse sine is defined from -\frac{\pi}{2} to \frac{\pi}{2} which lies in the 1st and 4th quadrant. So x=-\frac{\pi}{4}
  20. A

    How often do you need to refresh your memory?

    Some math topics you've studied you will rarely use again. How well do you find that you remember all the fine details of these topics that you rarely use? By the way, I'm back after one year. Anyone miss me?
  21. C

    Time is the refresh rate of conscious thinking

    I believe that time as humans perceive it, is a product of how often our conscious thought, or inner dialogue, accesses images of time passing. To illustrate this, consider a human watching the second hands move on a wall clock for 2 minutes straight. This person will feel like much time...
  22. tony873004

    Finding Online Calculus I Resources to Refresh Your Memory

    Are there any good online courses for Calculus I. Or maybe some VHS or DVD's I can buy that will basically give me what a first semester of what Calculus I would teach me? I want to take Calculus II. I already took and passed Calc I a few years ago. The problem is that I don't remember...
  23. C

    Ge force 2 monitor refresh rate fuziness above 60 Hz

    This is very technical. I've just got hold of a lovely Mitsubishi Diamondplus 230 sb monitor. It's only 2 years old and still under warranty. However I have a serious compatibility problem with my GeForce 2 MX 400 card. Thescreen luks fuzzy, not blurred at any refresh rate over 60 hz. In fact...
  24. B

    Refresh my memory on centripital force/acceleration

    Alright so we did this stuff at the beginning of the year and haven't touched it until now and I can't remember exactly how it works... Say a ball is being spun in a vertical circular path and you need to draw a FBD for it at the highest point and lowest point on the circle. At the top you...
  25. 6

    What do Fh and Fv mean in monitor specs?

    I have a viewsonic E771 and was wondering what the max refresh rate on in would be. I looked up the specs and it says Fh:30-70kHz, Fv:50-120Hz My question is what does Fh and Fv mean? -Burg
  26. C

    Understanding Newton's Laws: Solving Physics Problems with Ease

    Hi everyone, It's been a while since I've had physics. I can catch on quickly once pushed in the right direction but a friend is in a college level physics class that I once had and she needs help. I've tried to answer some questions but I don't know if my logic is right, or if I'm even...