F000:FFFEh               System Model ID

Length: 1 byte

This byte specifies the machine type.

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Use INT 15h, Service C0h, for a more accurate test of the system model
ID and the sub-model ID.

ID Machine Type
FFh Original PC
FEh Later PC, XT, or Portable PC
FBh Later XT
FDh PCjr
FCh AT or XT-286
F9h PC Convertible

Note that a few machines share IDs. To differentiate the machines, use
INT 15h, Service C0h, and look at the sub-model ID.