The Truth about CPUs

The Truth about CPUs

Pearl is confused. "So there's speed (the mhz stuff), and short-term memory (RAM) and long-term memory/storage (ROM)?"

Akili rumbles lightly, "Uh."

Akili rumbles lightly, "ROM is memory that does not change."

Pearl knew she didn't know much.

Akili rumbles lightly, "It *is* complicated."

Calin explains.

Akili could also, but lets Calin do it. :)

Calin says, "MHZ means how many thousand 'instructions' the computer can do per second."

Paw purrs, "I've 390something Megs of RAM."

says Cal, "how many million."

Calin says, "Ah, right."

Paw purrs, "Which is adequate even in a 2.something MHz computer methinks."

Calin says, "And that's still not EXACTLY right, as some instructions take more than one cycle."

Akili shakes his head to Paw. "Your current memory will not work in a newer motherboard."

Calin says, "Anyway, and instruction is a very tiny bit of stuff. Like doing one bit of arithmetic."

Pearl got it.

Calin says, "So his computer currently does 400million tiny things per second."

says Cal, "the older CPUs took several clock cycles to execute most instructions. the new stuff can do more than one per clock tick."

Calin says, "New computer are up over 3 ghz (billion per second)."

Pearl says, "Wow"

Calin says, "On to memory now."

Pearl nods.

Calin says, "RAM is like a big whiteboard. You can use it to help you do math, and to keep track of lots of things... it's very fast to write on and very easy to read, but it's only so big. And it gets erased every time the computer reboots."

Calin says, "A hard disk is like a file cabinet or a notebook. It's not as convenient as the whiteboard... it takes longer to write in, longer to look up what you want... but it doesn't go away when you reboot."

Pearl nods. "Short-term and long-term memory."

Calin says, "ROM is usually described next to RAM, but I'm not going to. It has no bearing on the current discussion."

Akili asides, "RAM also has different access speeds - how quickly it can be read and written to. Which is why the type of RAM you need will vary depending upon the type of mainboard you're using."

says Cal, "and RAM that can keep up with the CPU is EXPENSIVE."

Pearl asks, "CPU?"

says Cal, "microprocessor."

Akili rumbles lightly, "Calin's getting to it."

Calin says, "Yeah, sorry. The CPU is the part with the MHZ."

Calin says, "It's the part that executes instructions."

Akili rumbles lightly, "Stands for Central Processing Unit, if you're curious."

Pearl says, "Got it."

Calin says, "So there are several things that go into how fast (or slow) a computer is."

Pearl says, "I always thought the whole computer tower was called the CPU."

Akili smiles. "That's a common perception."

Pearl says, "Good to know these things!"

Calin says, "The CPU, the RAM, the hard disk, and the motherboard (or bus, or whatever - it's the glue that holds it all together)."

Calin says, "If you have a fast CPU, but very small ram... it will have to keep going to the long-term storage to get info, instead of keeping it all handy."

Pearl says, "So after knowing all this, it's just a matter of keeping up with the times to know the units, and what is currently on the market, and what your needs are."

Calin nods.

A still calm settles silently across the cool plants.

Calin says, "The one part that I didn't adaquately describe yet is the motherboard/bus."

Calin says, "I will use the two interchangeably for now."

Akili holds off on his comment until Calin finishes this section.

Calin says, "The motherboard is the part that moves information between the CPU, RAM, hard disk, and any other pieces (network, modem, etc)."

Pearl nods.

Calin says, "Motherboards have their own speed, and have limits about what kind of cpu, ram, etc they can use."

Pearl says, "AH."

Calin says, "The motherboard is usually much slower than the CPU, but that's not too bad."

Calin says, "The faster the better, of course."

Akili asides, "It's not uncommon for the CPU to run as much as ten times faster than the motherboard it's sitting on."

says Cal, "Cache."

Pearl blinks at Cal.

Calin says, "If the CPU is your head, and the RAM is the whiteboard, the motherboard speed is how long it takes you to read the board."

Akili rumbles lightly, "Cal's trying to jump ahead again."

Akili rumbles lightly, "We'll get to that."

Calin says, "Even if you're a slow reader, once you read it you can do lots of math in your head."

Paw purrs, "Oh... and a side note here... Floppy disks."

Pearl laughs!

"Eh?" asks Calin.

Paw purrs, "Floppy disks are MUCH slower than the Hard Drive."

Paw purrs, "MUCH MUCH SLOWER."

Calin says, "Oh. Well, yeah."

says Cal, "floppys are simular to small, slow hard drives."

Calin says, "That doesn't really effect how fast a computer will run programs though."

Pearl laughs at Paw. "I got it okay! I'll copy my files to hard drive from now on. :)"

Calin says, "Not these days."

Paw has caught Pearl working on files off of the floppy one too many times.

Calin chuckles. "Ah."

Paw purrs, "Usually complaining that her computer is soooo sloooooow."

Pearl swoons. "Such a sin!"

Akili rumbles lightly, "Even a CD or DVD drive can't keep up with a hard drive."

Calin says, "And those are MUCH faster than a floppy."

Calin says, "Anyway, I think I'm done with my explanations."

Akili grins. "A hard drive is as fast as you can go, while still being slow."

Paw purrs, "Yeah, but you wouldn't generally be editing a file on a CD or DVD."

"Any questions?" asks Calin.

Pearl says, "Nope. I don't think so."

Calin says, "Cool."

Akili finishes his earlier comment. "The often frustrating part is that while the speed of the CPU - the MHz rating - is important... it's not always an accurate comparison when looking at the speed ratings of different chips."

Pearl exclaims, "Good stuff!"

Pearl is lost again, Akili...

Akili smiles. "I'll explain."

Paw purrs, "So, in upgrading, I'd need a Processor, Motherboard and RAM."

says Cal, "the pentium 4 has really high clock speeds, but doesn't get as much done per clock tick as other chips."

Paw purrs, "Err... CPU = Processor."

Calin says, "Yeah, which makes me wonder what the point of the high clock speed is."

Paw asks, "How else will you rate it?"

says Cal, "sales to idiot customers."

Calin says, "I don't know."

Pearl asks, "mhz and now gigahertz are for CPU speed. What's RAM and ROM units?"

Pearl asks, "MB?"

Akili rumbles lightly, "Megabytes and Gigabytes, same as your hard drive."

says Cal, "the P4 was released before it was properly optomised because Intel needed a 'new CPU'."

Calin says, "The smallest unit of CPU speed is a hertz. The smallest unit of RAM and Hard disk is Byte."

Calin says, "And again, ROM has no place in this discussion."

Akili agrees.

Akili rumbles lightly, "Anyway, as I was trying to explain about CPU comparisons...."

Pearl listens to Akili.

says Cal, "ROM is used for getting started and little else these days."

Calin explains now, just so it doesn't feel left out. "ROM is read only memory. It stores just enough stuff to get the computer started booting, and that's the only part it plays."

Akili rumbles lightly, "Calin's statement about the millions of instructions a processor can run a second is quite correct. But nowadays, CPUs have built-in shortcuts. Rather than, say, run five instructions to solve five math calculations, one shortcut will allow you to do one instruction for those five calculations. So, for that particular math instruction, your CPU is effectively five times faster."

Akili rumbles lightly, "Even though the MHz is the same."

Akili asks, "Make sense?"

says Cal, "and multiple instructions can be run in parallel in some cases."

Akili rumbles lightly, "I'm oversimplifying, Cal, thank you."

Pearl asks, "So the chip makes the shortcuts?"

Calin nods.

says Cal, "the program has to be compiled to use the shortcuts."

Akili rumbles lightly, "Well, the chip offers them. The person writing the program has to know to use them. Those are those phrases like MMX, 3DNow, SSE, and other terms you might have heard in relation to CPU ads."

Akili rumbles lightly, "So, a 200MHz chip is just as fast as a 200MHz chip that offers those MMX code shortcuts. But when running the right program, the MMX-enabled chip can potentially run faster."

Akili asks, "Does that make sense?"

Pearl nods.

Akili rumbles lightly, "So that's one trick. There's a couple others."

The placid stillness silently falls across the cool bushes.

Akili rumbles lightly, "Some of the newer Intel chips have something they call Hyperthreading, which allows the chip to run two instructions on one clock tick. So, with the right software, your system will run twice as fast as the MHz rating."

Akili rumbles lightly, "There are many others, and I don't know them all. That's just an example of how the MHz rating isn't a straightforward comparison. AMD no longer rates their chips on the MHz speeds, for that very reason. And the last thing, that Cal mentioned earlier, is cache."

says Cal, "the old origional pentium could do 2 instructions at once, in very restrictive cases."

Akili makes sure Pearl is still following along okay.

Pearl says, "I'm with ya."

Pearl says, "So basically, I'll need an expert if I'm going to buy a motherboard with chip because I won't know how good it is."

Calin says, "Yeah, pretty much. But anything new is going to be significantly faster than what he has now."

Akili smiles. "Cool. Now, as was also mentioned earlier, RAM is your short-term, high-speed memory storage. MUCH faster than a hard drive, but temporary. Well, there's something else that's even faster. CPUs usually have even faster memory built into the chip itself, which is cache."

Pearl laughs

says Cal, "where RAM is like a whiteboard, cache is like a pad in your hand. smaller, but faster to use."

Pearl blinks. "Wait a sec. CPUs have a chip? I thought the motherboard had the chip..."

Akili rumbles lightly, "The CPU *is* a chip."

Pearl asks, "CPU=hard drive?"

Calin says, "CPU = Processor = Chip."

Pearl is lost then.

Pearl lemme review the log.

Akili rumbles lightly, "The motherboard is where the chip plugs in to."

Calin says, "The hard drive is that metal flat rectangle I know you've seen before."

Akili rumbles lightly, "Er, the CPU."

Pearl rolls her eyes.

Pearl exclaims, "Terminology!"

Calin says, "Yeh, it's not fun."

Akili rumbles lightly, "Notice that we haven't used the word 'computer' anywhere in this discussion. :)"

Pearl asks, "Okay, hard drive is what we were talking about before. MB. Long-term storage. Memory. Yeah?"

Akili nods.

Calin says, "Well, pretty much."

Calin says, "Though the word 'memory' usually means RAM."

Calin says, "But yes, the hard drive is long term storage."

Pearl asks, "CPU is not the tower. CPU is the processor. WHat's that then if not the hard drive. Hard drive include the motherboard? No. Motherboard is separate, with the chip?"

Akili rumbles lightly, "The CPU is your brain. It's what can do the math."

Calin says, "The tower is just the box that holds it all together."

Pearl laughs and thought she had it all.

Pearl says, "CPU is brain. Processor."

says Cal, "CPU does the thinking."

Akili rumbles lightly, "Right."

Calin says, "The CPU, RAM, and hard disk all plug in to the motherboard. RAM is usually like small circuit boards."

says Cal, "motherboard is a communications path."

Akili rumbles lightly, "The CPU has little to no 'memory' of its own, though. Which is why you have RAM."

Calin says, "The hard drive is a metal rectangle, about 3.5 inches by 6."

Pearl says, "I got that part. I think I'm confused on the difference between hard drive and RAM."

Pearl says, "Ok"

says Cal, "hard drive is mechanical, high capacity, slow."

Calin exclaims, "Oh, I know you'll get this one!"

says Cal, "RAM is all electronics, faster."

Calin says, "That thing that Paw takes back and forth to school is a hard drive in a plastic case."

Pearl says, "Right."

Calin says, "It's designed to plug in outside instead of inside, but it's the same thing."

Pearl says, "So the hard drive has RAM"

Calin says, "Nope."

says Cal, "The hard drive has storage."

Pearl laughs out loud!

Calin says, "The hard drive stores data, and RAM stores data, but they are not the same thing."

says Cal, "RAM has smaller, faster storage."

Pearl says, "Oh right."

Calin says, "The whiteboard instead of the file cabinet."

Akili rumbles lightly, "You cannot afford an amount of RAM equal to the size of storage you have on a hard drive. :)"

Pearl says, "So hard drive is like a large floppy."

Calin says, "Yes."

Akili rumbles lightly, "Right. A very large, very fast floppy."

Pearl glares at Akili. "But hard drive and floppy aren't measured in speed. They're storage SPACE/memory."

says Cal, "hard drive, floppy, CD, DVD, all hold data on the surface of a disk of some sort."

Calin says, "You are correct."

Calin says, "Hard drive and floppy do have speeds, but we're usually more interested in the capacity."

says Cal, "Hard drives have a speed rating, but that's secondary to storage size."

Pearl says, "CPU is speed. How fast it processes. MOtherboard is the go-between, in speed."

The placid stillness quietly falls through a chilly fog.

Calin says, "Yup."

Pearl asks, "RAM is storage space, but also speed?"

Calin says, "RAM is fast storage."

Calin says, "Fast temporary storage."

Pearl says, "Or is it how RAM and CPU work together that determines RAM speed."

says Cal, "yup. you want enough RAM to hold what's being worked on."

Calin says, "I don't think we should worry about ram speed for now."

Pearl says, "Okay."

Calin says, "Just think of it as fast storage."

Pearl says, "Got it."

Akili rumbles lightly, "Fast, but temporary storage."

Calin says, "How much you have will effect overall system speed though."

Calin says, "And here's why:"

Calin says, "If on your whiteboard you can write a whole page of math, you can easily see any part of it."

Pearl asks, "So big hard drive to save my monterous file. Fast CPU to grab it for me. Fast motherboard to bring it to RAM so I can see it. And lots of RAM to see it quickly?"

Cal hears a speed demon driver spin out and pass at dangerous speeds.

Calin says, "On the other hand, if you only have room to write one tiny equation... you'll have to erase and rewrite SO much to do that same amount of math."

Akili rumbles lightly, "Lots of RAM to contain the entire contents of that monsterous file."

Calin says, "That sounds right, Pearl."

Pearl whews.

Pearl says, "I'm set. Nobody say anything else now. :)"

says Cal, "though there are circuits to read and write the hard drive without needing the CPU to be constantly involved."

Calin zips it.

Akili rumbles lightly, "Well, I was mentioning cache. :)"

Akili rumbles lightly, "But that can pass."

Calin glowers.

Pearl cracks up!

Akili puts on sunglasses.

Pearl asks, "You guys are so funny. Sure, Akili, what's cache?"

says Cal, "cache is to RAM what RAM is to the hard drive."

Pearl says, "Got it."

Pearl says, "The hand notebook."