Single vs. multi core speeds. How does that work???

I was exposed to computers back in the mid 80's and instantly had an interest in them, though I never had my own until around six years ago. Today, it might be considered a dinosaur in the computer world, but it worked well for what I wanted it to do and I learned a lot from it.

One thing I've never really understood was when they came out with multi-core systems. How does the speed rating work?

I was looking at new computers today, not looking to buy, just looking and drooling as I usually do, and noticed two made by the same manufacturer one with a single core rated around 2Ghz and a dual core rated at 1Ghz. Everything else was pretty close to the same including the price.

I was just wondering, would a single core system rated at 2.0Ghz be the same as a dual core system rated at 1.0Ghz?, and if so, would there be any benefit to having a dual core rather than a single?

Or would the dual core system be two 512Mhz processors paired to get to 1Ghz?, or am I way off and it's something completely different???


Also, back before multi core systems, they had processors that didn't give a Ghz rating, just a number like 2500. How does one know the speed rating of those?


Thanks to anyone who can answer and sorry if this has been asked before. I asked here because there's a lot of members here who don't seem to mind helping others and are a lot smarter than me.

reply to post by Americantrucker


Well, the best way to look at it is this way.

You have a 1 lane highway, this is the single core processor.

You have a

It's the architecture of the chipset that is changing every few years, you can't simply view it as an increase of Ghz over time.

The architecture progression recently Pentium->Dual Core->Core 2 Duo->Xeon->i5/i7

You can only compare the Ghz rating for processors with similar architecture.

Think of the processor as a sort of water wheel.....where the flow of the water in Cubic Liters/second is the total amount of processing power. The speed at which this water wheel turns can be represented by the clock speed in Ghz - the faster it turns, the more water flows.

But the architecture of the processor...this is the design and size of the water wheel. The number of scoops it has on it, the size of each scoop (possibly the Cache Size), the wideness of the wheel (I/O Bandwidth), how much water can be scooped in one turn of the wheel....the effectiveness of the wheel is determined by its design, its architecture.

By thinking of it this way, it makes sense how a more efficient or differently designed water wheel can pass more water than an older design that just spins simply faster and faster. Because eventually it spins so fast that water just splashes everywhere and the water wheel becomes inefficient, That's why new architecture gets invented, rather than just making the old architecture go faster.

Originally posted by Americantrucker
I was exposed to computers back in the mid 80's and instantly had an interest in them, though I never had my own until around six years ago. Today, it might be considered a dinosaur in the computer world, but it worked well for what I wanted it to do and I learned a lot from it.

One thing I've never really understood was when they came out with multi-core systems. How does the speed rating work?

I was looking at new computers today, not looking to buy, just looking and drooling as I usually do, and noticed two made by the same manufacturer one with a single core rated around 2Ghz and a dual core rated at 1Ghz. Everything else was pretty close to the same including the price.

I was just wondering, would a single core system rated at 2.0Ghz be the same as a dual core system rated at 1.0Ghz?, and if so, would there be any benefit to having a dual core rather than a single?

Or would the dual core system be two 512Mhz processors paired to get to 1Ghz?, or am I way off and it's something completely different???


Also, back before multi core systems, they had processors that didn't give a Ghz rating, just a number like 2500. How does one know the speed rating of those?


Thanks to anyone who can answer and sorry if this has been asked before. I asked here because there's a lot of members here who don't seem to mind helping others and are a lot smarter than me.

Yeah, for multi-core processors you can just multiply to find the equivalent single core processor.

So a 2 Ghz quad core would be a 8Ghz single core.
I'd go with the dual core equivalent over a single core.
Really though, I wouldn't go with anything less than a quad core, with today's prices and technology.

Originally posted by Ghost375
So a 2 Ghz quad core would be a 8Ghz single core.
I'd go with the dual core equivalent over a single core.
Really though, I wouldn't go with anything less than a quad core, with today's prices and technology.

Nope, that is absolutely not how it works.

Read my post above, more cores does not equal more processing power - it just allows for data to be processed on more than one core.

The speed rating of the CPU is the speed rating for the CPU, 4 1.0ghz cores does not = 4.0ghz, it equals 4 cores traveling at 1.0ghz simultaneously.

Now, if you had an application that perfectly threaded the information to be processed between all 4 cores, then yes - that single application would be "theoretically" processed at 4.0ghz - but not really, it's just splitting the workload and being processed at that speed on each core.

High end multiple cores are only usefull for high end applications.

Multiple cores make for less diminishing returns on performance when your CPU(s) is/are heavily loaded.

You won't really notice the difference if you are just the average home user browsing the internet.

So if ur weighing what to buy, always consider what you DO with your PC and adjust to that.

You don't need a OMGWTFPWN system for normal daily use. Only if you play games too and wanna keep up with the games released nowadays, u'll have to replace your PC or at least parts of it (graphics and memory) within half a year.

Thanks for all the quick replies. I wasn't expecting that.

The only question I have now is, let's use b3l13v3's example, for a 2.4ghz multi-core processor, be it a dual or quad core, how do they come to 2.4ghz?

reply to post by Americantrucker


That is the clock-rate of the CPU, or how fast it completes operations(square wave electrical pulses, 0s and 1s)

Originally posted by Americantrucker
Thanks for all the quick replies. I wasn't expecting that.

The only question I have now is, let's use b3l13v3's example, for a 2.4ghz multi-core processor, be it a dual or quad core, how do they come to 2.4ghz?

Think of each core a separate CPU. Each CPU core can run at 2.4ghz, so they dont combine the 2 speeds. You will often hear people say they have a 6ghz CPU because they have 2 cores running at 3ghz but that is wrong, they do not have 6ghz CPU's. They just have 2 lanes to transfer information at 2.4ghz. Like one poster said, if you have a water wheel and you turn up the speed really fast its just going to slosh water around. But if you have 2 water wheels you can get more. I would chose a 1core 2ghz CPU over a 1ghz dual core CPU.