A disk drive that is enabled by information contained in a mode page and in a command to access data blocks of either a small size (e.g., 512 bytes) or of a large size (e.g., 4,096 bytes). This allows legacy application software written for 512 byte sized blocks to run without change. By turning on the 4,096 byte sized block flag in the command, new software written to obtain improved performance benefits may also be used with the disk drive. The dual block capability is implemented in software.