It protects PCB from power surges of external power supply. Such drives should have at least two shock sensors.Īnother protection device called Transient Voltage Suppression diode or TVS diode. On some drives shock sensors can detect even lightest vibrations and signals from such sensors would help VCM controller to tune up heads movements. It theoretically should protect the drive from further damage but practically it doesn't, so don't drop your drive - it wouldn't survive. VCM controller immediately parks heads and sometimes spins the drive down. Shock sensor can detect excessive shock applied to a drive and send signal to VCM controller. Sometimes there is no flash chip on PCB that means content of the flash is located inside MCU.
#Computer hard disk drive code
Without such code drive wouldn't even spin up. When you apply power to a drive, MCU chip reads content of the flash chip into memory and starts the code. The core of VCM controller can withstand working temperature of 100C/212F.įlash chip stores part of the drive's firmware. It controls spindle motor rotation and heads movements. This fellow consumes the most of electircal power on PCB. Next chip is Voice Coil Motor controller or VCM controller. CPU eats up some memory to store firmware modules and as far as we know only Hitachi/IBM drives show real cache size in data sheets for the other drives you can just guess how large is the real cache size is. Because memory logically divided on buffer or cache memory and firmware memory.
![computer hard disk drive computer hard disk drive](https://ae01.alicdn.com/kf/Hd18dc7dca5004f6c90a3273712508b2aG/WD-BLUE-500GB-Internal-Hard-Drive-Disk-3-5-7200RPM-16M-Cache-SATA-III-6Gb-s.jpg)
This PCB has Samsung 32MB DDR memory chip which theoretically means the HDD has 32MB cache (and you can find such information on a data sheet for this HDD) but it's not quite true. Capacity of the memory chip defines capacity of the cache of HDD. The Memory is DDR SDRAM memory type chip. MCU also has IO ports to control everything on PCB and transmit data through SATA interface.
![computer hard disk drive computer hard disk drive](https://thumbs.dreamstime.com/b/computer-hard-disk-drive-1860235.jpg)
On modern HDDs MCU usually consists of Central Processor Unit or CPU which makes all calculations and Read/Write channel - special unit which converts analog signals from heads into digital information during read process and encodes digital information into analog signals when drive needs to write. The heart of PCB is the biggest chip in the middle called Micro Controller Unit or MCU. Now let's remove PCB and see electronic components on the other side. The black painted aluminum case with all stuff inside called Head and Disk Assembly or HDA. PCB holds in place and wires electronic components of HDD. The fancy piece of green woven glass and copper with SATA and power connectors called Printed Circuit Board or PCB. We going to tear to pieces 1TB Seagate ST31000333AS drive.