Introduction to solid-state disks

Maintenance, Test & Measurement, Calibration

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December 2001 Maintenance, Test & Measurement, Calibration

A solid-state disk (SSD) uses memory chips such as flash, SRAM or EPROM to store programs and data instead of the magnetic particles used on mechanical disks. SSDs can directly replace both floppy drives and hard drives while maintaining complete DOS compatibility.

When the system boots, the disk card modifies the BIOS INT-13 disk I/O routine. The routine then translates read/write commands to the disk card so that they will correctly access the memory chips. Special drivers are not necessary, the user simply sets the drive to act as drive A: or C: and uses standard DOS commands (COPY, DIR, etc) to manipulate the data.

It is also easy to boot from a solid-state disk. Simply set the jumpers on the disk to emulate drive A: (the 1st FDD). Copy the application files to the disk along with the standard system files required to boot (command.com, io.sys, autoexec.bat, etc). The next time the computer is started, it will boot directly from the solid-state disk EPROM, SRAM and flash memory EPROM (erasable programmable read-only memory) provides storage that is nearly nonvolatile - it is written electrically and can only be erased by UV light. SRAM is fast RAM memory and is volatile, but if it has a battery back-up, it will keep its data when the power is off. Flash memory operates like an EPROM, except that it can be programmed and erased while on-board. It provides the same long data retention but reduces the time required to store the data.

Why solid-state disks?

Faster data access and other advantageous characteristics make solid-state disks a solution that is well suited for critical commercial or industrial applications. Mechanical disks are highly susceptible to breakdown in severe industrial environments. Solid-state disks give faster and more efficient operation, a longer life span, and a lower risk of breakdown or data loss.

Flash/RAM/ROM disks appear in applications that demand a large storage capacity, easy memory expansion, complete DOS compatibility and security. Compared to mechanical disks, solid-state disks can withstand more severe mechanical conditions.

Watchdog timers make standalone or unmanned operations much easier to manage because they can automatically trigger resets or reboots. Applications that generate lots of data will find ample storage space on a disk card.

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Maintenance, Test & Measurement, Calibration

Introduction to solid-state disks

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