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4 Momentus Product Manual, Rev. D
3.0 Drive specifications
Unless otherwise noted, all specifications are measured under ambient conditions, at 25°C, and nominal
power. For convenience, the phrases the drive and this drive are used throughout this manual to indicate the
Momentus models.
3.1 Specification summary table
The specifications listed in this table are for quick reference. For details on specification measurement or defi-
nition, see the appropriate section of this manual.
Table 1: Drive specifications for 640, 500 and 400GB models
Drive specification ST9640322AS ST9640320AS ST9500320AS ST9400321AS
Formatted GB* 640 500 400
guaranteed logical blocks 1,250,263,728 976,773,168 781,422,768
bytes per physical sector 4096 512 512 4096
Physical read/write heads 4
Discs 2
Cache (MB) 8
Recording density in BPI (bits/in avg) 1560k
Track density TPI (tracks/in avg) 325k
Areal density (Gb/in
2
avg) 507
Spindle speed (RPM) 5400
Average latency (ms) 5.2
Internal transfer rate (Mb/s max) 1175
I/O data transfer rate (MB/s max) 300
ATA data-transfer modes supported SATA 1.0, Serial ATA Revision 2.6
PIO modes 0–4
Multiword DMA modes 0–2
Ultra DMA modes 0–6
Height 9.5 +/- 0.2 mm (0.374 +/-.008in)
Width 69.85 mm +/- 0.25 mm (2.75 +/- 0.010in)
Length 100.35 + 0.20 / - 0.25 mm (3.951 + 0.008 / - 0.010in)
Weight <100 g (0.220 lb)
Power-on to ready (sec typical) 3.6
Power-on to ready (sec max) 4.5
Standby to ready (sec typical) 2.5
Standby to ready (sec max) 3.5
Track-to-track seek time, read (ms typical) 1.5
Average seek, read (ms typical) 13.0
Full-stroke seek, read (ms max) 27.0
Startup current, +5V (max) 1.0A