A Helpful Guide Of PC, Mac & Notebook Memory/RAM

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Extra RAM can make a huge difference to your pc, notebook or Mac. A RAM upgrade is so cheap and cost effective compared to any other upgrade yet offers a great boost to your machines’ performance & improves your computing experience overall. It is an easy upgrade too in most cases.

Ebay is a great value place for buying RAM (sometimes reffered to as DIMM) but getting the right RAM is essential, as is buying from a suitable, experience Ebay seller (always check feedback!)

Most modern systems run Windows XP which should really be run on at least 512mb RAM and while it will run on machines with less RAM you may find the experience somewhat sluggish. With a RAM upgrade this should change and the user should find programs opening & performing faster. Depending on the tasks you use your pc for you may find 1gb or even 2gb+ of RAM better suited to your needs.

There are many different types of RAM & I appreciate it can be confusing to the majority of people who are not familiar with the technology. I am writing this guide to hopefully assists others to work out the type of RAM they need and the options available to them.


Desktop RAM measures approx 13.5cms long & looks similar to the pictures below. While there are many different types of RAM, the current variants you are most likely to encounter are listed below (in age of release order):

SD-RAM – Comes in PC100 (133MHz) and PC133 (133MHz) speeds
DDR RAM – Comes in PC2100 (266MHz), PC2700 (333MHz) and PC3200 (400MHz) speeds
DDR2 RAM – Comes in PC2-3200 (400MHz), PC2-4200 & PC2-4300 (533MHz), PC2-5300 (667MHz), PC2-5400 (675MHz), PC2-6400 (800MHz) etc


SD-RAM is identifiable as it has two notches in the gold coloured teeth along the bottom. DDR & DDR2 RAM have a single notch in the gold teeth & while these two types look very similar they are physically different as the gold notch is in slightly different places to each other.

There are variances on the above types including RAM designed for servers and professional/industry platform motherboards. This type of RAM is ECC registered RAM, but the high majority of normal desktop pcs will run NON-ECC, unregistered RAM.


Not all RAM is compatible with all motherboards/laptops. For example if your pc/mac/laptop requires PC133 SD-RAM it can normally use either PC100 or PC133 RAM however if your pc/mac/laptop requires PC100 it can often only use PC100 RAM so its very important to get the exact RAM you require.

With DDR & DDR2 RAM most boards will accept any speed within the same group type. In other words a board that needs DDR RAM will normally accept PC2100, PC2700 & PC3200 RAM but not any DDR2 type RAM. Likewise if a board requires DDR2 RAM it will normally accept PC2-3200, PC2-4200, PC2-4300, PC2-5300, PC2-5400, or PC2-6400 RAM but not any DDR RAM (which is pyhsically different).

Sometimes the user may find that despite they have installed faster RAM, it may only be recongised as a slightly slower spec (eg PC3200 RAM shows as 333MHz instead of 400MHz). This occurs when the RAM speed is limited by the board itself. Sometimes this can be overcome by a BIOS update or just left as is, working at the slightly lower but max spec capable by the motherboard.

This highlights how important it is to buy the correct RAM. There are various ways of checking what type of RAM you have in your system and the type of RAM you need for it. If You remove the side of your pc you can physically look at it and it should have a sticker on that either says what type of RAM it is or take a note of the model number of the RAM. By Googling the model number you can soon find out the type of RAM you have and need.

While the side is off your pc you can also check your motherboard number, again by Googling this or going to the manufacturer’s website you can soon find out type of RAM you require as well as the maximum about of RAM of pc will take.

Alternatively you can use a small utility program that will also tell you this information. Programs like “CPU-Z”, “aida32ee_393” or “Sandra2007” (larger and more thorough than the earlier two) are all system diagnosis programs that will all give you the information you need. (Please note the above three programs are all Windows based programs, for Mac’s simply Google your Mac model number for full information of the type of RAM you need).

Once you have this information you can soon work out what type & the amount of RAM you need and your motherboard will take.


Laptop / Notebook RAM comes in the same types and speeds as desktop RAM, the only difference being size. Laptop / Notebook RAM is commonly referred to as SODIMM and is a smaller version of the RAM mentioned above. It measures approx 7cms in length and is about half the size of full-sized desktop RAM.


The same techniques can be used as mentioned in the Desktop & Macs section to find out what type of RAM you need with the exception of the 'removing the side panel' option. Nearly all notebooks have two user upgradeable RAM slots and with the majority of notebooks these are generally located on the underside of the notebook under their own separate protective panel. Normally by removing this small panel you will find two RAM slots and you can upgrade the RAM easily without having to dismantle the rest of your notebook. There are some exceptions where RAM might be instead located under the keyboard or in other areas on more specialist, smaller notebooks.

As with desktop pcs It is always best to check the maximum amount of RAM your machine will handle. Some notebooks are surprisingly limited when it comes to RAM upgrades and since most notebooks only have two upgrade slots you may find yourself with some excess RAM once you have completed your upgrade. At least one slot will currently have a RAM module installed already (running your notebook) while some manufacturers might even have filled both slots already (meaning you will have to remove at least one of these modules to install a higher capacity of RAM).


When installing RAM first check you have the correct type & the amount you are installing will not exceed the maximum your motherboard/notebook will facilitate for. Before handling any RAM (either your old or new RAM) always ensure you are statically discharged. This is best done by either using a specialist wrist-band connected to a grounding point or by touching a suitable metal surface (i.e your pc case) to discharge any static from your body.

When installing RAM turn power down your pc/apple/notebook (if turned on) and turn off at the wall (for notebooks, remove the battery as well). Internal components may still be hot if the machine has been recently used so best leave a little time after use before installing new hardware. 

To install new RAM open the grips/tabs at either end of a spare RAM slot and using the cut away teeth on the RAM module as a guide ensure you have the RAM the right way round (gold teeth insert into the slot and any notches should line up with those on the RAM slot). Install the RAM at a slight angle pushing the RAM into place until the grips/tabs at either end of the slot move back into the closed/locked position. Your RAM should now be installed correctly, replace any removed parts (covers, screws etc), reconnect your power source and power on your pc/Mac/notebook.

If using Windows XP the amount of RAM you have will be displayed under "System" in your computers "Control Panel" (sometimes found under settings from your Start Menu) or you can use one of the system diagnosis programs listed above to verify your new RAM has been recognised by your system. Please note some machines share their RAM with onboard graphics (if no separate graphics card is being used) so sometime RAM may show a little less than expected (i.e 16, 32 or 64mb less).


Different types of RAM has a different number of pins and while no-one expects the user to count these it is always useful to have a reference table telling you the number of pins each tpye of RAM module has. This is useful when searching for RAM on Ebay (see my other guides for help when searching Ebay).

LAPTOPS/NOTEBOOKS - 144 Pin RAM is SODIMM SD-RAM while 200 Pin is DDR SODIMM RAM. DDR2 RAM is also 200 Pin but not cross-compatible with laptops requiring DDR RAM.

DESKTOPS PC/MACS - 168 Pin RAM is desktop SD-RAM, 184 Pin RAM is desktop DDR RAM and 240 Pin RAM is desktop DDR2 RAM.


If after/during the reading of this guide you do not feel comfortable carrying out a RAM upgrade yourself then it is probably best not to risk it. I am sure someone you know will be experianced enough with pcs/noetbooks to carry out the upgrade for you. 

I appreciate there are of course other types of RAM which I have not covered in this guide but in the interest of making this text as simple as possible I have stuck to the main types of RAM used.

Hopefully this guide has been of assistance to you and helped you work out the type and amount of RAM you need. Why not bookmark it for future use or add me as a favourite seller?

This guide has been written and created by Peter Shaw. My Ebay User ID is SFFPCS & my listings can be accessed as nromal through eBay or directly through the domain name (which  redirects to eBay) www. sffpcs.co.uk.  Thank you for reading this guide. If this guide was helpful please select YES on the bar below asking Was this guide helpful?. Thank you for your time

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