Toshiba has introduced highest density 1TB 2.5-inch hard drive for portable and form factor mobile computers. Ideally, the new high density HDDs are meant for consumers who fall short of storage space for their laptops. The 9.5 millimetre thick 2.5-inch MK7559GSXP HDD has two-platters holding 750GB capacity and is almost like regular notebook HDDs. Also, 12.5 millimetre thick 2.5-inch MK1059GSM HDD model has three platters offering 750GB and 1 TB storage space. The sample shipments will start from next month. However, there is no word on pricing as yet.     
Both new Toshiba HDDs use the company's own technology to improve the perpendicular magnetic recording technology head and disk. Inspite of the different number of platters and capacities, both different height HDDs have few things in common. 
Both share the same 5400RPM spindle speed, 8MB buffer memory, 12 millisecond seek time and SATA 2.6 3Gb/s interface.
Also, both 2.5-inch HDDs have Toshiba's 'Silent Seek' technology that makes every data seek operation quieter just like an idle drives. The MK1059GSM 1TB model with three platters consumes slightly more energy 2.2W in seek mode and 1.7W in read/write mode compared to 1.85W and 1.5W for 750GB model, respectively.
This means you'll soon be able to go for high-density HDDs for your laptops and store more data on it. However, do note that these new HDD models may not fit into older laptops.