Flash memory question

[olsaltydog]

Currently working on a paper assignment for my A+ class and for some reason I cannot seem to grasp this concept or at least what the question wants. So looking for help in understanding what I dont understand.

Question: Research the flash memory underlying ROM BIOS chips. Identify basic features and describe limitations.

I am assuming this is asking about the change between the older EEPROM chips that would have to be completely removed in order to get updates where now you can flash the BIOS or use a utility like Intel's for instance to update the BIOS.

Now I see this as also a possibility of asking about how the system initially activates and will go through the initial process of turning everything on before handing the system over to the operating system.

Any help is appreciated, I wont lie, I am enjoying learning things but some topics I seem to make them harder then they need to be. Getting an outside perspective usually allows me to put the pieces together. Thanks ahead of time.

 

[Pinhedd]

Currently working on a paper assignment for my A+ class and for some reason I cannot seem to grasp this concept or at least what the question wants. So looking for help in understanding what I dont understand.

Question: Research the flash memory underlying ROM BIOS chips. Identify basic features and describe limitations.

I am assuming this is asking about the change between the older EEPROM chips that would have to be completely removed in order to get updates where now you can flash the BIOS or use a utility like Intel's for instance to update the BIOS.

Now I see this as also a possibility of asking about how the system initially activates and will go through the initial process of turning everything on before handing the system over to the operating system.

Any help is appreciated, I wont lie, I am enjoying learning things but some topics I seem to make them harder then they need to be. Getting an outside perspective usually allows me to put the pieces together. Thanks ahead of time.

There are several types of memory that are suitable for storage of the platform firmware. Many of these types were previously unsuitable and have become suitable over time, while others have been made obsolete.

The oldest type of ROM is EPROM, or Erasable Programmable Read Only Memory. These chips can still be found and are easily identifiable by a small transparent window in the middle of the chip. These devices can be programmed electrically, but cannot be erased electrically. Erasure is performed by exposing the device to ultraviolet light for a period of time. The use of EPROM in personal computers would have been problematic, and the technology was largely obsoleted by EEPROM by the time the PC was introduced. EPROM is fast, and word addressable, but the inability to reprogram it electrically makes it largely unviable.

NOR EEPROM, or Electronically Erasable Programmable Read Only Memory, became the mainstay of PC firmware for over 30 years. EEPROM has many desirable qualities which make it particularly suitable for the sensitive task of holding PC firmware. Like EPROM, EEPROM is fast and word addressable. Word addressability means that the microprocessor can execute instructions located on the EEPROM directly without having to load the contents into memory. This makes EEPROMs suitable for holding the computer's startup, initialization, and testing code. Once the system's memory has been initialized, the system firmware can be copied from the EEPROM to the system memory for faster execution.

NOR Flash. Flash Memory is the successor technology to EEPROM. It is similar in some aspects, but has many key differences. EEPROMs are designed with reliability in mind, and samples are tested to be fault-free. To elaborate on this, many commercial EEPROM and NOR Flash chips specify write endurance of around one million cycles. Compare this to the 50,000 cycles on a high end SLC-NAND SSD, or 3,000 cycles on a block of Samsung TLC-NAND Flash. This is essential because a fault in an EEPROM could compromise the integrity of the boot code. A key difference between Flash memory and EEPROM memory is the method of reprogramming. EEPROM memory is erasable and reprogrammable in very small blocks, nominally one byte. This allows each byte of a firmware image to be erased, reprogrammed, and validated byte by byte. NOR Flash typically groups data into blocks of which the contents can be programmed individually but must be erased collectively. This increases the complexity of programming the device. NOR Flash is the storage mechanism of choice for most modern motherboards that use UEFI firmware.

NAND Flash. NAND Flash is the type of memory used in most SSDs and portable storage devices. Unlike NOR EEPROM and NOR Flash, NAND Flash is not word addressable and thus is not suitable for in-place execution. Thus, NAND Flash must be used with a small boot ROM (often embedded in the CPU) which is capable of loading the contents of the NAND Flash that are essential for configuring the platform's memory into the CPU cache. The storage density of NAND Flash is many times higher than the storage density of NOR Flash for a chip of comparable size. However, the endurance of the device is significantly diminished. Thus, NAND Flash is typically only used to store firmware in environments which are size constrained such as mobile phones and tablets.

 

[olsaltydog]

I figured this question had to do with the changes over the course of time. The different iterations we went through to get to where we are today. Thanks for the help in clarifying the question.

Seems I put too much thought into this as the last question he had for us, wanted to know about the underlying structure of PCIe and that turned into the 3 layers controlling PCIe. So I was kind of expecting something along those lines but again thanks.