2 computer questions...

quarryman

one easyish, one maybe not.

1. when a CPU or RAM is rated at xxxMHz or GHz what does that describe exactly? For instance a 2.8GHz Pentium 4 can perform 2,800,000,000 operations per second.

Assumming a CPU processes 1s and 0s does this mean that an operation is one step of these binary digits?

OR

is it the assumption that since a binary number represents a number say '4' and another is '5' then an operation is maybe 4+3, which means its processing 16bits per operation?

I'm trying to define operation i guess, sorry if this is hard to explain.

2. 2nd question. what is the fastest speed RAM on the market? and what speed does flash memory operate at in MHz?

Khannie

Ok, not a simple question, but I'll take a stab at it.....

2.8GHz means that there is a signal entering the chip which changes from one, to zero (and reaches the point where it's going to go back to one again) 2.8 billion times per second. This "clock signal" determines how quickly the various parts inside the cpu function.

Clock speed has been used as a simplistic measure of speed for x86 chips (intel / amd) for some time, although it is not really accurate as a measure of computational ability, it's useful as a quick and dirty number.

Your first question is really two questions, I hope that answers the first part.

In answer to "what's an operation?":
CPU's can perform certain tasks in hardware (e.g. add, subtract, compare, logical and, logical or, etc.). Each type of CPU has an "instruction set" of these things that can be performed in hardware by it. I would consider an operation to be one instruction (but that will take more than one clock cycle AFAIK).

CPU's can also be measured by their ability crunch MIPS (millions of instructions per second).

Modern CPU's have various techniques that they use to speed themselves up beyond raw MHz GHz numbers. I'm wandering here.....

As for the RAM question. Sorry, don't know. I use PC3200 which runs at 400MHz. I don't think that there's an AMD chip with a faster FSB than that at double data rate.

Hope this helps!

quarryman

great that's a little clearer now. from reading around it seems things work at the bit interface speed of the chip. so a 32-bit chip such as the P4 will shift 32 bits of data in one go (ie one clock cycle).

fastest DDR I can find at the moment is DDR4500 which opereates at 566 MHz which is 283 MHz. These chips run with a 64bit interface so it moves 64 bits 566 million times a second. fast. am i on the right track? that's not allowing for any delays so it still needs to be modified by RAS and CAS and refresh delays.

Paulw

AFAIK Rambus RAM runs faster than DDR.

quarryman

Originally posted by Paulw
AFAIK Rambus RAM runs faster than DDR.

it does. but it works on 16bit instead of 64bit for DDR. ie it runs faster to moves less data per cycle.

unkel

Originally posted by quarryman
fastest DDR I can find at the moment is DDR4500

OCZ announced DDR4800 a few weeks ago which is the equivalent of 600MHz

joc_06

For any digital processor to work it needs a clock signal and a voltage source - gnd and vdd - 3.3v usually for cmos, ttl =5v

a 2.8ghz processor means that it is a processor that is rated to be clocked at 2.8ghz +-.1% i think (this allows people to overclock)

after that then it will have an instruction set - assembly
each instruction take a certain no of clock to complete

hence a 2ghz athlon can compare to a faster clocked p4 allegedly

secret_squirrel

Originally posted by joc_06
For any digital processor to work it needs a clock signal

Just to complicate things afaik some processors dont need clock signals (some ARM chips?)

Modern CPU's can do more than 1 operation per clock cycle. Have a read about pipelines and related stuff. Another good example would be modern gfx chips which can abuse a pixel (lets keep it simple) in all sorts of horrible ways in one clock cycle.

If I remember rambus operates faster but actually has a higher latency.

Double data rate (DDR ram) can be read 2x per clock cycle. (Once as the clock signal hits 1 and once as the signal is about to switch down to 0.) Double/Quad pumping fsb's works in the same way.

Flash memory is rather slow in comparison since (I believe) it takes much longer for the chips to change from a 1 to a 0, since the chips are designed to keep their state when there is no power. (so its not quick as a flash )