Tag Archives: RAM

Computer Structure – Main Memory

OK I may have went a little overboard on EEPROM 🙂 but it is very very useful. Some of you might think that EEPROM and flash memory is the same thing but you would be wrong. Have a look at this from webopedia

Pronounced double-ee-prom or e-e-prom, short for electrically erasableprogrammable read-only memory. EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. Like other types of PROM, EEPROM retains its contents even when the power is turned off. Also like other types of ROM, EEPROM is not as fast as RAM.

EEPROM is similar to flash memory (sometimes called flash EEPROM). The principal difference is that EEPROM requires data to be written or erased onebyte at a time whereas flash memory allows data to be written or erased inblocks. This makes flash memory faster.

Our new PCs

Well I finished setting up the new machines today, and even as I type this, the network should have finished installing software on them and is shutting them down.

I took one of the machines out for a bit of a test to see what it could do, but before I comment on that, lets look at the specs.

  • i5-2400 processor
  • 4GB RAM
  • Windows XP 32bit
  • 512MB GPU (can’t remember the model right now except it was a radeon)

The machines are in a slimline case and look OK for a HP.  I loaded up most of the games that were too slow for my old machines; warsow, world of padman, etc. I set the graphics options to max and had a look at the frames per second – rock solid on 75+FPS, which means they should be fast enough for anything we want to do.

One thing though, the desktops are only reporting 3GB, why is that and what can we do about it?

Factors that effect Computer Performance.

Lots of things effect computer performance. We were looking at a few of them in today’s lesson.

Different types of RAM can have a big impact on the performance of a computer system. Why? Data has to be moved in and out of RAM, the quicker this data can be accessed and moved the faster the processor can get to processing it. Cache improves performance, this high speed SRAM is located close (often in) the processor. It allows the contents of RAM to be stored close to the processor, the processor check here for the next instruction, if its not found then it checks RAM. Although this sounds a bit haphazard, cache can improve the performance of the machine quite significantly.

Then we recapped how RAM effects performance.

  • More RAM means less need to use virtual RAM, therefor an increase in speed.
  • Cache allows for faster access then when the processor gets a cache hits the contents are transferred quicker. there are different types of cache.
  • Increases in RAM speed has failed to keep up with the increase in RAM capacity but different RAM has different clock speeds and even different ways of access.

We went on to look at how the speed and type of a peripheral can effect performance and that they require an interface. The interface allows the CPU to talk to the peripheral. (some brief notes below but we will look at this in more detail in a future post)

Functions of an Interface

  • Buffering – holding data temporarily while in transit between the CPU and peripheral.
  • Data Conversion – changing data into a form the CPU can understand and vice-versa – protocol conversion e.g.
    • serial to parallel
    • voltage conversion
  • Handling Status Information – to show whether the device is ready to receive or send data e.g. is the printer ready or out of paper.

A big thank you to Mr. Allen in Airdrie Academy for letting me cut up and publish his revision notes – AA Computer Performance


Right by now you should deep in study and the difference between SRAM and DRAM may be giving you some grief. Have a look at this article.

Basically, SRAM is fast and expensive and DRAM is less expensive and slower. Now, there is a lot more to it than that so get out your notes and go look it up. P46 of the Scholar notes has this to say

SRAM chips are very fast but are not suited for very large amounts of memory. They are more suited to cache memory, where only small amounts are required. You will learn more about cache memory when we look at factors that affect system performance.
DRAM chips are more widely used. They are much cheaper to produce, can hold larger amounts of data in a smaller physical area and require less power. They are dynamic, requiring a continuous signal to refresh the contents of the chip.