Memories

No, this is not one of those posts where I go back… well maybe it is, but not as usual.

You see, when I was still in junior high, I can remember about memories, that is computer memories. At that time, most computers used the doughnut shaped pieces of iron called ferrite cores. Each core could store one bit. To store 4 bits, the equivalent of one digit took 4 cores — though they generally organized them differently.

At the time, the frustration was packing as many of those doughnuts into as small a space as possible and still make them useful. The last successful core memory I saw provided about 512 million bits (64 million bytes) in a cabinet 6’x4’x2′ and it weighed, with power supply, roughly 6 or 7 hundred pounds.

Since that time, they came out with what they call IC memory, which has a history all of its own. It is enough to confuse all but the most avid computer geek. The first ones weren’t all that impressive… 4 flip-flops inside one computer chip. Before they were of any real use it took thousands of them. Moreover, they required a lot of electricity to power them.

Over time, they put hundreds, then thousands of the flip-flops in one chip and they called it static RAM. They were static in that as long as they had power, the info in the memory remained in tact. They were Random Access because any one flip-flop could be accessed as quickly as any other. I am not going to go into how they did this. If you want to know, simply do a search on Static RAM memory and I am sure you will find far more than you want to know.

Now, if there is going to be a static RAM, there really ought to be a dynamic RAM as well and there is. Dynamic RAM has 3 advantages. It is smaller, uses less power and generates less heat. There are trade offs. It is slightly slower and it requires more complex circuits to support it.

One of the problems with the prior types of RAM is that, when you turn off the power, anything stored is gone. Hence they came up with ROM, Read only memory. It is set once and forever. This is neat but for one thing. It can never be altered. If you need to change what is in the memory, you have to change the memory, that is the chips themselves.

Then someone came up with PROM, EPROM and EEPROM. I told you it gets complicated. PROM is ROM that can be written, that is programed once. As with ROM, if you need to change it, you have to toss it and replace it. EPROM is the same as PROM but it can be erased by using ultraviolet light to erase it. Hence, it can be reused. Finally, EEPROM is Electronically Erasable PROM. That is to say, it can be erased by sending it a signal to erase it. Then it can be re-written as if it were a new PROM.

Now they have a new type that can be rewritten thousands, maybe millions of times. They put them in computers and use them to replace the Hard-drive. (incidentally, Hard-drives have a history all their own. Being as I want to finish this some time today, I’ll skip that for now.)

The modern computer has at least 3 types of memory. There is at least some form of ROM used to store what is BIOS. It contains enough to get the computer started and a little more. The instant the computer is turned on, the microprocessor fetches its first instruction from ROM and performs what is called a bootstrap, or boot for short.

The second form of memory is dynamic RAM. Generally, most of the memory is dynamic RAM. Many if not most computers don’t use ROM once the computer is fully booted. ROM is far slower than RAM. Finally, the computer starts using the static RAM which is faster than dynamic RAM. The two types of RAM are used in combination for high storage and speed.

Having said all this, it would seem there are those types of memory that fail. I am one of those who has become well aware of it. Alzheimer’s disease just kind of sneaks up on us and it can get so frustrating. I can feel it sneaking up on me and I have seen it in others around me. It is just too bad we can’t come up with an answer for that.

There was a paper I saw one time. It was a farce about WOM, write only memory. It was said that a professor cam up with the idea as he saw his students taking notes he knew they would never look at. However, the idea is not that new. Egyptians wrote inside pyramids and never intended for anyone to read it.

Here lately, I get this feeling that my memory is becoming a WOM. More and more I misplace things. I can search for words, maybe an hour… words I have used all my life. I am starting to get an idea of what it is like to lose my memory. I am beginning to get a feel for what it is like for others.

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