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The new model hasn’t got much louder. Here are the comparative acoustic characteristics of the 7K250 and 7K400:

As you can see, there’s only 1dB of difference between the three- and five-platter models. This was made possible by the improved design of the drive.

 
Top panels of the 7K400 (left) and 7K250 (right)

Take note of the screw that had previously disappeared on the transition to motors on liquid bearings. This screw is here again because of the new motor whose axis is fixed from two sides. Another innovation is a special latch that locks the actuator when the heads are parked on the ramp, thus preventing the heads from touching the surface of the disc at an accidental shock. This latch has been ported from the SCSI drives of the UltraStar series and will be useful for the hot-swapping feature which is declared for the Serial ATA version of the 7K400.

Another server-friendly technology is the special Rotational Vibration Safeguard (RVS) system that helps the drive to sustain vibration without losing in speed. Several hard drives in one system case always create some vibration which can knock the heads off the necessary track and bring about a considerable time loss due to the repositioning of the heads back. The electronics of the 7K400 have two acceleration sensors that keep track of vertical and horizontal vibration. The data from the sensors are used for dynamic correction of the position of the heads. This is how Hitachi estimates the efficiency of this system (the 100% point is the performance of the drive in WinBench without any vibration):

It should be noted that performance loss due to vibration may occur with a single drive, too, if it is not firmly fastened in the system case. So, this technology is undoubtedly a welcome feature. Now let’s take a look at the bottom of the drive, at its electronics.

 
The electronics of the 7K400 (left) and 7K250 (right)

You can see one new chip here – a TSOP-packaged chip of SDRAM memory. The memory had previously been on the reverse side of the PCB, but putting five platters into a standard-size case limited more the thickness of the electronics. The fetch time is 7.5 nanoseconds which corresponds to 133MHz frequency.

We can also see that the Serial ATA interface is still implemented by means of a translator chip, so we can forget about Serial ATA Native Command Queuing here. Instead, they have grafted a new command set for processing streaming data into the electronics.

 
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