Random-access memory

What to Do If Your RAM Isn’t Detected By Your PC

RAM is one of the most essential parts of your desktop computer, and it’s also one of the quickest and easiest parts to upgrade. Modern RAM modules are incredibly simple to use, so it’s rare that something goes wrong in installation…but then when something does go wrong, it gets frustrating quickly. If your computer or operating system doesn’t recognize the RAM you’re using, here’s what you need to do to find the problem.

Step One: Check The Seating

On a desktop, installing RAM is simple: fold back both the clips on the RAM slot, then insert the stick firmly straight down. The pressure from your insertion should force both clips to snap back into a locked position with an audible “click,” but sometimes it does require you to snap them back down on the DIMM manually. If the DIMM isn’t exactly perpendicular to the slot and the motherboard, or the clips can’t be completely snapped, it’s not fully inserted. Remove the DIMM and try again.

Laptop designs, due to their lower tolerances for space and volume, are a little trickier. Assuming your laptop allows access to a RAM DIMM slot at all (many newer, smaller designs don’t), the DIMM is generally inserted at an angle, then pushed down towards the laptop frame until it clicks into place. Even a properly-inserted DIMM might not be seated properly; be sure to put as much pressure on the stick as you can without risking damage to the circuit board itself.

Step Two: Check Your Motherboard’s Compatibility

RAM DIMM sticks are fairly standard and well-designed: they can only be inserted one way on both desktops and laptops, desktop and laptop RAM isn’t interchangeable, and different generations of RAM won’t fit in the wrong socket (so a motherboard that only supports DDR4 RAM can’t physically fit DDR3).

That being said, it’s rare but possible that RAM might not be compatible with a motherboard, even if it’s the right type. RAM speed should dynamically shift down if it’s faster than the slot itself can handle, and timings shouldn’t have an impact on the compatibility at all. But it’s possible the RAM DIMM’s capacity is higher than the motherboard is rated for.

Your motherboard has a maximum amount of supported RAM, which includes all the slots on the board taken together. This might be as few as…

NIST Helps You With Cryptography

Getting cryptography right isn’t easy, and it’s a lot worse on constrained devices like microcontrollers. RAM is usually the bottleneck — you will smash your stack computing a SHA-2 hash on an AVR — but other resources like computing power and flash code storage space are also at a premium. Trimming down a standard algorithm to work within these constraints opens up the Pandora’s box of implementation-specific flaws.

NIST stepped up to the plate, starting a lightweight cryptography project in 2013 which has now come out with a first report, and here it is as a PDF. The project is ongoing, so don’t expect a how-to guide. Indeed, most…

The Complete Guide to Speeding Up Your Virtual Machines


Virtual machines are demanding beasts, providing virtual hardware and running multiple operating systems on your computer at once. As a result, they can sometimes be a little slow. Here are some tips to help you squeeze every last drop of performance out of your virtual machine, whether you’re using VirtualBox, VMware, Parallels, or something else.

Create Fixed-Size Disks Instead of Dynamically Allocated Ones

When creating your virtual machine, you can create two different types of virtual disks. By default, virtual machine programs will generally use dynamically allocated disks that grow as you use them.

For example, if you create a new virtual machine with a dynamically allocated disk with a maximum size of 30 GB, it won’t take up 30 GB of space on your hard disk immediately. After installing your operating system and programs, it may only take up 10 GB. As you add more files to the virtual disk, it will expand up to its maximum size of 30 GB.

This can be convenient, as each virtual machine won’t take up an unnecessarily large amount of space on your hard drive. However, it’s slower than creating a fixed-size disk (also known as a preallocated disk). When you create a fixed-size disk, all 30 GB of that space would be allocated immediately.

There’s a trade-off here: a fixed-size disk uses more space on your hard disk, but adding new files to the virtual machine’s hard disk is faster. You also won’t see as much file fragmentation. The space will be assigned in a large block instead of being added in smaller pieces.

Install Your Virtual Machine Software’s Tools

After installing a guest operating system inside a virtual machine, the first thing you should do is install your virtual machine software’s drive package—Guest Additions for VirtualBox, VMware Tools for VMware, or Parallels Tools for Parallels. These packages include special drivers that help your guest operating system run faster on your virtual machine’s hardware.

Installing the package is simple. In VirtualBox, boot your guest operating system and click Devices > Insert Guest Additions CD Image. You can then launch the installer from the virtual disc drive in your virtual machine. On VMware, select the Install VMware Tools option in the virtual machine’s menu instead. In Parallels, click Actions > Install Parallels Tools.

Follow the instructions on your screen to complete the installation. If you’re using a Windows guest operating system, it’ll be just like installing any other Windows application.

Ensure you keep these updated with your virtual machine program. If you see a notification that an update is available for Guest Additions or VMware Tools, you should install it.

Exclude Virtual Machine Directories In Your Antivirus

Your computer’s antivirus program may be scanning your virtual machine files whenever they’re accessed, reducing performance. The antivirus can’t see inside the virtual machine to detect viruses running on your guest operating systems, so this scanning isn’t helpful.

To speed things up, you can add your virtual machine directory to your antivirus’s exclusions list. Once it’s on the list, your antivirus will ignore all files in this directory.

Ensure Intel VT-x or AMD-V Is Enabled

Intel VT-x and AMD-V are special processor extensions that improve virtualization. Newer Intel and AMD processors generally include these features. However, some computers don’t automatically enable them. You may have to go into your computer’s BIOS and enable this setting yourself, even if your computer…