CMOS really hasn’t changed very much from what I could find on the internet… Mainly the speeds have increased and the noise has been reduced it also went from analog to digital. Originally, the IBM PC only used of a small portion of CMOS memory and the balance of the 64 bytes were left undefined. Once other manufacturers cloned the AT form factor it wasn’t long that other areas of the CMOS was used by various BIOS manufacturers for such user-selectable options as memory wait states, memory type, initial boot drive selection, boot-up clock speed, hard drive interface type, green options, shadow RAM options, cache options, and password protection of the CMOS contents. It still uses a small battery incase there is a power outage and still uses volatile RAM. The size of the CMOS memory has also pretty much stayed the same because there is no need to increase the size.
There was never any need to store more than 512 bytes in the memory as it holds the absolute basic boot settings for the system. The typical size is still 512 bytes currently. All it comes down to is “If it isn’t broken don’t fix it.”, so it’s been that way since almost the very beginning. It does its job which is to just get the computer started and make sure everything is in place and then hands it all over to the computers. Complementary Metal Oxide Semiconductor, or CMOS, is a widely used type of semiconductor. CMOS semiconductors use both NMOS (negative polarity) and PMOS (positive polarity) circuits. Since only one of the circuit types is on at any given time, CMOS chips require less power than chips using just one type of transistor.
This feature makes them convenient for use in battery-powered devices such as laptops. Personal computers also contain a small amount of battery-powered CMOS memory to hold the date, time, and the system setup parameters. To access the CMOS on most computers, press the delete key as the computer is booting. CMOS has made changes over the years. CMOS memory has been changed from analog to digital. Another important change is the speed has increased. CMOS has also made changes in regards to noise reduction. In regards to size, CMOS memory has remained relatively unchanged over the years. It is only required to hold the basic boot settings for the system and so there was no need to increase the memory size. However, the size of the CMOS memory changes on the way it is set. Memory has the ability to be added or reduced from the computer. Over the years, CMOS has evolved into using EEPROM. CMOS does, at times, still use a battery on the motherboard but EEPROM is more popular. EEPROM is considered an advance feature and, as a result, has not yet been accepted by the majority of the market.