Editing VM CPUs and RAM

Virtual machine hardware settings determine the amount of Metered RAM and CPU capacity that the VM consumes—larger VMs consume more Metered RAM and CPU capacity. For information about how Metered RAM and CPU capacity are calculated, see How usage is calculated.



To edit the VM CPU and RAM settings
  1. Make sure the VM is fully powered off (not running or suspended).
  2. Before making hardware changes to your VM, create a template of it. If any problems occur, you can restore your VM from this template.
  3. Navigate to the VM Settings > Hardware page.

    hardware settings

  4. Next to CPUs, select the number of CPUs that the VM will use.

    If an x86 VM is hardware version 10 or newer, click Advanced to see multi-core CPU options. By default, Skytap configures 1 CPU core per socket.


    • The maximum number of CPUs for a single VM varies, depending on region. For a list of regional capabilities, see Skytap Cloud features by region.
    • If an x86 VM is hardware version 9 or earlier, you can upgrade the VM hardware version to make advanced CPU configuration options available. For instructions, see Upgrading VM hardware versions.
    • The number of cores per socket must be 1, 2, 4, or 8. Only valid CPU configuration options are displayed.
  5. Next to RAM, enter The amount of RAM (in MB) that the VM will use.


    • The amount of ram (in GB) must be equal to or greater than the number of CPUs.
    • The maximum amount of RAM available for a single VM varies, depending on region.
    • For x86 VMs – Increasing the amount of RAM, also increases the IOPS performance (up to 16 GB of RAM).
    • For Power A CPU architecture that supports IBM i, AIX, and Linux (on Power) in Skytap Cloud. VMs – Increasing RAM enables higher Entitled capacity (effectively increasing CPU performance). For specific details, see the CPU Entitled capacity lookup table below.
    • For Power A CPU architecture that supports IBM i, AIX, and Linux (on Power) in Skytap Cloud. VMs – The minimum supported RAM is 2048 MB (2 GB).
  6. Click Save.

Additional information

  • Follow vendor recommendations for the operating system and the installed applications when setting the CPU and RAM values. Generally:

    • Additional CPU cores permit more concurrent system and application processes, which improves system performance.
    • Additional RAM allows more applications to be active and improves access speeds for data.
  • Some VMs may not support every configuration option that Skytap allows you to set. The guest OS type and hardware version number determine the amount of CPUs and RAM that a VM can use.

    For example:

    • Windows Server 2008 R2 Standard VMs support a maximum of 4 CPUs. If you select 8 CPUs, 4 of those CPUs are ignored by the guest OS.
    • VM (x86 The most common CPU architecture. x86 CPUs support Windows and Linux VMs in Skytap Cloud. ) hardware versions 9 and earlier don’t support 12 CPUs or 256 GB of RAM. For example, if you select 12 CPUs for a VM on hardware version 7, you may see an error message when the VM runs.

RAM lookup table

These tables provide GB-to-MB conversion values for common RAM settings.

1 1024   9 9216   24 24576   192 196608
2 2048   10 10240   32 32768   224 229376
3 3072   11 11264   48 49152   256 262144
4 4096   12 12288   64 65536   320 327680
5 5120   13 13312   80 81920   384 393216
6 6144   14 14366   96 98304   448 458752
7 7168   15 15360   128 131072   480 491520
8 8192   16 16384   160 163840   512 524288

You can copy the MB value you want and paste it directly into the Hardware RAM (MB) field on the Hardware tab of the VM Settings page.

CPU Entitled capacity lookup table

For Power VMs, set Entitled capacity (and approximate IBM i CPW) by changing the amount of RAM and the number of CPUs.

The Entitled capacity (and approximate CPW) values in the table below are guaranteed when the corresponding RAM and CPUs are configured for the VM.

CPU Cores
RAMEntitlementCPW *EntitlementCPW *EntitlementCPW *EntitlementCPW *
0-31 GB0.121,2740.252,6250.373,9290.505,309
32-63 GB0.252,6550.505,3090.757,9641.0010,618
64-95 GB0.373,9290.757,9641.1211,8921.5015,927
96-127 GB0.505,3091.0010,6181.5015,9272.0021,236
128-159 GB0.626,5831.2513,2731.8719,8562.5026,545
160-191 GB0.757,9641.5015,9272.2523,8913.0031,854
192-223 GB0.879,2381.7518,5822.6227,8193.5037,163
≥ 224 GB1.0010,6182.0021,2363.0031,8544.0042,472
* CPW values are approximate.


  • Currently, a single IBM i VM supports a maximum of four CPU Cores (approximately 42,472 CPW).
  • Existing active Power VMs will display calculated Entitled capacity (and approximate IBM i CPW) values but those values are not applied to the VM until it’s completely shut down, and then started again.