RAM Use and Available Hard Disk Space in Photoshop Adobe Photoshop manages image data in two ways: first it allocates hard disk space, also known as scratch disk(s), for all image data, then it uses random-access memory (RAM) to cache this data for editing images. The amount of hard disk space that is available to Photoshop determines the maximum amount of RAM (i.e., working space) Photoshop can use. This document will help you understand the relationship between available hard disk space and RAM usage in Photoshop. Because it much faster to access information in RAM than it is to access information on a hard disk, Photoshop processes image information using RAM to decrease the number of times it must read from and write to the hard disk. The more RAM you allocate to Photoshop, the more data Photoshop can cache and process in RAM, and the quicker Photoshop can process an image. Photoshop will only use the amount of RAM equal to or less than its scratch disk space, no matter how much RAM is installed or allocated to it. Therefore, the amount of available hard disk space set for your scratch disk(s) must be equal to or greater than the amount of RAM you want Photoshop to use. For example, if you want Photoshop to use 200 MB of RAM, you'll need at least 200 MB of available hard disk space designated for Photoshop's scratch disk(s). If Photoshop seems to take longer to process images than you expect, you may have less available hard disk space than RAM allocated to Photoshop. This means you may need to free additional space on the hard disk(s) designated as Photoshop's scratch disk(s), or specify one or more additional scratch disk. To ascertain whether you need more hard disk space, first determine the amount of hard disk space available to Photoshop and the amount of RAM allocated to Photoshop. Then, compare these values. To determine Photoshop's RAM and Scratch Disk allocations: 1. In Photoshop choose File > Preferences > Plug-Ins & Scratch Disks. 2. Note the disk(s) listed in the Scratch Disks section. Click Cancel. NOTE: Startup is the disk containing the Windows directory. 3. Choose File > Preferences > Memory & Image Cache. 4. Note the Photoshop RAM value under the Physical Memory Usage area. Click Cancel. 5. From the Desktop, double-click the My Computer icon. 6. Right-click a hard disk noted in step 2 and choose Properties. 7. Note the Free Space value in the second column and it's unit of measurement (e.g., MB or GB). Click Cancel. 8. Repeat steps 6-7 for any remaining hard disks noted in step 2. 9. Add the values from steps 7-8. 10. Complete steps under Converting and Comparing below. Hard disk space is generally measured in megabytes (MB) or gigabytes (GB) while RAM is generally measured in kilobytes (K). To compare your available hard disk space value to Photoshop's RAM allocation value, both values need to be in a common unit of measurement (e.g., MB or GB). Thus, you will need to convert Photoshop's RAM allocation value from K to MB or GB, whichever is the unit of measure used for your available (Mac OS) or free (Windows) hard disk space. Use one of the methods below to convert K into the same unit of measurement as your hard drive. After you have a common unit of measurement, use the instructions under Comparing to subtract the RAM value from the available hard disk space value and analyze the results. Converting from K to MB If you noted MB as the unit of measurement in step 7, divide the value you noted in step 4 by 1,024. This will give you the amount of allocated RAM in MB. You will compare this value to your available hard disk space value (see Comparing). For example, if the value noted in step 4 is 22968K, your equation will look like this: 22968K 1024 = 22.429688 MB indicating you have 22.429688 MB of RAM allocated to Photoshop. Converting from K to GB If you noted GB as the unit of measure in step 7, divide the value you noted in step 4 by 1,048,576. This will give you the amount of allocated RAM in GB. You will compare this value to your available hard disk space value (see Comparing). For example, if the value noted in step 4 is 22968 KB, your equation will look like this: 22968K 1048576 = 0.021903991GB indicating you have 0.021903991GB of RAM allocated to Photoshop. After you convert your allocated RAM value to the same unit of measure as your hard disk, subtract the RAM value from the hard disk space value (determined in step 9 above) and analyze the results. For example: If the value determined in step 9 is 50 MB, and your converted, allocated RAM is value is 22.429688 MB, your equation will look like this: 50 MB - 22.429688 MB = 27.570312 MB If the value determined in step 9 is 5 GB, and your converted, allocated RAM is value is 0.021903991GB, your equation will look like this: 5 GB - 0.021903991 GB = 4.978096 GB If the difference is zero or greater (i.e., a positive number), you have the same amount of or more available hard disk space than RAM allocated to Photoshop and Photoshop is able to use all the RAM allocated to it. If the difference is less than zero (i.e., a negative number), you have less available hard disk space than RAM allocated to Photoshop and Photoshop is unable to use all the RAM allocated to it. To enable Photoshop to use all its allocated RAM, you need to free additional space on the hard disk(s) specified as Photoshop's scratch disk(s), or specify one or more additional scratch disk(s) in Photoshop. In simple terms, placing a temp file on the disk when loading means that the available RAM PhotoShop is set to use; is simply not there.