I recently decided to upgrade the amount of RAM in my primary PC from 2 GB up to 4 GB. I have received a copy of Adobe Photoshop CS3 Extended upgrade and would like to work with as much RAM as possible. As well I will be doing some Video Editing on my primary PC as well (while my Video Editing Station is down waiting for its upgrades). DDR2 Ram is also very cheap right now so I decided to take advantage of it.
When I built the PC a few months ago I installed 2 GB of Kingston DDR2 533 RAM in it and it has been working well. I ordered 2 GB of DDR2 667 RAM for a new AMD machine I am building soon, then with the low prices I decided to order a another 2 GB of RAM. I figured I would put the 4 GB of 667 RAM in my main machine and put the 533 in the AMD machine I am building. The first two sticks of Kingston Value Ram I ordered turned out to be Double Sided memory (Ram chips on both sides of the chips), the second set (same part numbers) was single sided. The Intel manual for the board said it could handle both, both so I went ahead with the upgrade. The machine was working well but then the processor would start to spike at 100% usage and the system would lock up for up 2 to 3 minutes (and as long as 5 minutes) from time to time. I removed the new RAM put the old RAM back in and everything was fine again. I then tested each pair of RAM individuals (DS and SS) and again everything tested and worked fine again. I went back to the 4 GB and the system started on the processor spikes again. The motherboard bios correctly detected all of the RAM 4096MB and Windows Vista Ultimate saw the 3508 MB of RAM (explanation of why down below).
Next I tried changing the order of the pairs on the motherboard and while the system was a little better, it would still spike the CPU every so often. In frustration I picked up 2 more GB of Kingston Value RAM again yesterday but this was a matched RAM kit and was double sided. I removed the Single Sided sticks of RAM, installed the new Double Sided, restarted and everything was fine again and has been running without the CPU spikes.
My motherboard is an Intel DG695WH (one of their higher end desktop boards) and it did indicate that it could handle both types of RAM. The manual says nothing about installing Single Sided and Double Sided RAM together. Nor would it work with the Double Sided 533 DDR2 and the Double Sided 667 RAM either (which in theory all 4 sticks should have run at 533).
So while everything appeared to be fine with the mixed types of RAM it wasn’t. This may not happen on all motherboards, but to be safe if you are planning an upgrade of your memory, or are having problems after a RAM upgrade, ideally try to get identical RAM if you can (if you have DS RAM, get DS sticks).
I indicated earlier that Windows Vista Ultimate only sees 3508 MB of RAM while the motherboard sees the full 4096 MB. This is a function of any 32 bit operating system, and the same thing would happen if I did this to a Linux machine or a Mac. The operating system cannot see memory above the 4000MB mark. If I go ahead and install a 64 bit version of Windows or another OS on this machine, it would see the entire amount of RAM. This is something that you should keep in mind when doing upgrades as well.
With the extra RAM that I have now (4 GB) I am going to build and AMD machine with an Asus motherboard to see if 1) it will run with 533 and 667 DDR2 RAM and 2) if it will run with the double and single sided sticks. The plan is to also install a 64 bit version of Vista on the system as well. Otherwise it looks like my Media Center PC will get the additional 2 GB 533 RAM and the AMD will run with only 2 GB.
Remember that the best upgrade you can do to virtually any computer is to upgrade the amount of Memory in it to improve performance. I use this simple analogy to explain hoe memory upgrades work for my clients.
Think of an Office desk as the amount of RAM that you have in your computer, then a filing cabinet (or a bookshelf) as your hard drive, your eyes as the display and you are the processor. You can only open so many files (or programs) on the desk before you start running out of desktop space (remember your operating system uses some of this desk too). When the desk fills up with stuff, you have to start putting stuff in the filing cabinet. You get up move stuff to the cabinet then sit down. When you are dome with something you put it back in the filing cabinet. This is what happens on your computer. When the physical RAM fills up (opening programs and files) it starts to store open data on the hard drive, which is slower. Think of a RAM upgrade as an upgrade of your desk. If you double the amount of memory in your PC, you essential double the size of the desk. Now you can open more work and still have space on the desk. You can switch back and forth between programs and files faster than if you had to run to the filing cabinet every time to get something.
I am going to create another post with this analogy soon as I like this one too much to bury it solely in this blog post.