Difference between HDD/SSD and ROM

[AlfreyCruz]

Yeah.. the title says it all.... cause I'm pretty confused their difference... Any help? lols I am the guy who knows what are the different CPU sockets in the MoBo are and the guy who knows 3 languages in programming.. but don't know where ROMs and HHD differ........

 

[Shektron]

ROM cannot be edited, it's like a fixed set of instructions that are usually executed when the PC is booting. These are usually hard-coded into the hardware itself, and cannot be changed or deleted. As for HDD and SSD, these are just storage devices used to store user and OS data, like movies, music, Windows files, etc. ROM is usually not read even by the OS, it's a very low-level storage which can't be easily accessed.

 

[Pinhedd]

Yeah.. the title says it all.... cause I'm pretty confused their difference... Any help? lols I am the guy who knows what are the different CPU sockets in the MoBo are and the guy who knows 3 languages in programming.. but don't know where ROMs and HHD differ........

ROMs, or Read-Only-Memory, are a type of non-volatile memory that are designed to be infrequently rewritten or never rewritten.

Solid state ROMs have existed for decades and are the starting point of booting a computer.

Some solid state ROMs, such as mask-roms, are fabricated with a particular set of stored data and are otherwise not programmable. PROMs are programmable, but not necessarily erasable. EPROMs are erasable through manual means (eg, exposure to ultraviolet light), and EEPROMs are electronically erasable.

Most solid state ROMs are designed to support what's called 'execute in place'. The ROM stores a very simple boot program that is executed when the microprocessor is released from reset. This requires a few considerations:

1.) solid state ROMs must have a very simple logical interface. No software drivers or host controller should be necessary. Simple addressing from the microprocessor should be enough.

2.) ROMs must be predictable and deterministic. They must operate without prior configuration.

Many microprocessors have embedded boot ROMs that sense various IO pins on the microprocessor to determine how it is configured, and how to load the next firmware stage. A lot of my development boards feature DIP switches which allow me to configure the FPGA/Microprocessor with firmware from different sources or storage mechanisms.

Many ROMs can be rewritten, but unlike many other forms of non-volatile memory such as NAND/Nor Flash, and magnetic hard disks ROMs are generally very slow to erase and have a very limited number of erasure cycles. Whereas a particular NAND memory cell may be rated to 50,000 erase/program cycles, an EEPROM may be rated to only a few hundred at most. With that said, once a programmable ROM is programmed... it will stay programmed for a very, very long time.

Other non-solid-state types of ROMs exist too of course, such as CDs and DVDs. Most of these are programmable once through burning, but some can be erased and reprogrammed if they are designed to be.