Hands on: Upgrading your system memory

Everyone knows that adding Ram to a PC can seriously improve its performance, but as explained in the last Performance column, it can start getting surprisingly tricky beyond 2GB.

First of all you’ll need a motherboard which can physically accommodate more than 2GB of Ram, along with a chipset and Bios that can recognise it. You’ll also need an operating system (OS) that knows what to do with it.

In last month’s column we looked at the issues of upgrading to 4GB of Ram, and as promised we’re back this month with even more ­ 6GB to be exact. So read on to find out what you’ll need to support this much Ram and whether it’s worth bothering.

Test system
We’re using the same base PC configuration as last month, an Asus P5W DH Deluxe motherboard fitted with an Intel Core 2 Duo 6700 processor. This motherboard features four DDR-2 memory slots into which we fitted a pair of 2GB Dimms alongside a pair of 1GB Dimms, making 6GB in total. The actual memory type was PC2-6400 DDR2 800 from Crucial and we used the memory advisor tool at www.crucial.com/uk to ensure we were getting the correct memory for our system.

Most 32-bit desktop OSs can address up to 4GB of Ram and overheads with devices mean you’ll normally only see 3.2GB. To use more Ram you need a special 32-bit or a 64-bit OS. To support a 64-bit OS you’ll need a processor that understands 64-bit instructions. AMD and Intel processors have been ready for some time. Your hardware will need 64-bit drivers.

We installed Vista Ultimate 64-bit on a 500GB Samsung hard disk, before disconnecting it and installing the 32-bit version on an identical disk in order to allow us to make direct comparisons. To address 4GB or more on a 64-bit OS, you’ll also need to enable Memory Remapping in the Bios. This should be disabled for a 32-bit desktop OS.

Results
To test the benefits of 6GB of Ram we used one of the most memory-hungry mainstream applications around: Adobe Photoshop CS3. Like most mainstream applications it is only available in 32-bit code. This means it will only get to use a maximum of 1.7GB of Ram under a 32-bit OS, or 3GB on a 64-bit OS. But there are still benefits to running it on a 64-bit OS with lots of Ram.

Under 32-bit Vista we opened a 300MB TIFF in Photoshop CS3, converted it to 32-bit and added a layer. By default Photoshop allocates 55 per cent of your available Ram, which meant it had 924MB to play with under our 32-bit configuration. The resulting file size far exceeded this, which meant virtual memory would be required. We performed an unsharp mask filter on the file, which took two minutes and 23 seconds with heavy disk access. Allocating more Ram to Photoshop accelerated this figure at the cost of lowering the performance of other applications running at the same time.

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