A Noob Question/Rant On Clock Speeds w/ Low-Powered CPU's?

[bmichaels556]

So... I have a few computers that I use. For when I'm just out and about and need some very basic computing power, I'm generally running an Asus E403S (Penium N3700 w/ 4GB RAM). I guess it's like, the ultra cut down version of a Zenbook, or whatever lol. For when I'm on vacation or whatever, I usually bring along my Dell laptop, which has an i3 4010U. It's not great by any means, but is much snappier and does what I need it to do overall. Some basic GIMP work, basic 1080p video editing. Ya' know, doing a bunch of cuts where I need them, things like that. Nothing too heavy, so it works just fine. Plus, I edited 1080p video for WAY too long on an old AMD Turion laptop from 2007, so I'm not too picky when it comes to doing these things on a laptop lmao. And finally, my main rig right now is a dual Xeon X5675 w/ 24GB of RAM that I got for way cheap and souped out myself.

 

But I can't help but ask this: Why does it seem like clock speeds on low-powered mobile CPU's are a lie? For example... The i3-4010u is running at 1.6 Ghz as far as I remember. Everything is snappy enough, given the horsepower it has. On Cinebench, it scores like a 60 single-thread. Yet it still feels just fine w/ an SSD, so I'm SURE that a lot of perceived performance and snapiness doesn't come from the CPU I suppose. At least in my experience.

 

But then look at this Asus laptop w/ the Pentium 3700. It scores ~40 on cinebench single core, but feels way more than 33% "slower". Not that it's an easy thing to quantify. But it's sort of a "I know it when I feel it" type of thing. But another weird thing I notice is this: The Pentium N3700 is at 1.6 Ghz and boosts to 2.4 Ghz. So why then, does it feel so damn slow in real-world usage? So yeah, I'm aware it's a low-power CPU. So if it's hitting a power limit, I get that's going to slow down. BUT, it's consistently hitting the advertised 2.4 Ghz on all cores. I'm SURE that while the RAM in a budget laptop like this isn't the best, that it's "good enough" to not be the cause of the whole system feeling like it's crawling. I also get that the storage on these speeds is often that eMMC stuff, which (I believe) is usually about as fast as a mechanical hard drive despite being solid-state. 

 

If I assume that it's true that this thing is hitting 2.4 Ghz, and that it performs 33% worse numbers-wise as a 1.6 Ghz i3 series CPU... That could ONLY mean that for whatever reason, the IPC on these particular lines of CPU's, is ATTROCIOUS, and only half as good as the standard "Core" series. My question is, WHY?

 

Are these architectures (Airmont for the 3700 I believe) specifically designed to hit super low power usage, but for some reason have inherently terrible IPC? Because that seems to be the case here. But then why does it even exist in the first place? Is it really cheaper for intel to have a whole dedicated line for this junk, as opposed to the Core-M series? Because THAT is more indicative of what you'd expect out of these kinds of low-powered CPU's that are clocked really low, but still offer respectable performance for what they are. But that doesn't happen with these. Why the hell do they exist then, as opposed to just releasing Core M's to the OEM's that are clocked low? Even the lowest-performing Core M I can find (the 5Y10a) has similar passmark scores, but I GUARANTEE it absolutely wrecks a 3700 in real-world performance in all aspects..

 

I guess this is just a huge rant, but also me trying to wrap my head around all this..

 

 

[Mira Yurizaki]

Lower power CPUs are designed to make sacrifices that do cut into IPC. There may be less cache, which eats up a lot of die space. There may be fewer things on the front end, which eat up die space and consume power. Historically out-of-order execution wasn't even on mobile processors until recently because the power needed to feed an OoE system was too much to justify the increased performance.

 

Also note that a lot of cheap PCs, like in the realm of less than $300 USD, aren't going to be using higher speed SSDs. If there is an "SSD", it's likely an eMMC type SSD which for all intents and purposes is like running off a somewhat fast SD card.

 

Also what's "real world usage"? Because for browsing the web to do things like check mail or whatever SNS you use, lower power processors are adequate.

Edited August 19, 2019 by Mira Yurizaki

[astranger200]

55 minutes ago, bmichaels556 said:

So... I have a few computers that I use. For when I'm just out and about and need some very basic computing power, I'm generally running an Asus E403S (Penium N3700 w/ 4GB RAM). I guess it's like, the ultra cut down version of a Zenbook, or whatever lol. For when I'm on vacation or whatever, I usually bring along my Dell laptop, which has an i3 4010U. It's not great by any means, but is much snappier and does what I need it to do overall. Some basic GIMP work, basic 1080p video editing. Ya' know, doing a bunch of cuts where I need them, things like that. Nothing too heavy, so it works just fine. Plus, I edited 1080p video for WAY too long on an old AMD Turion laptop from 2007, so I'm not too picky when it comes to doing these things on a laptop lmao. And finally, my main rig right now is a dual Xeon X5675 w/ 24GB of RAM that I got for way cheap and souped out myself.

 

But I can't help but ask this: Why does it seem like clock speeds on low-powered mobile CPU's are a lie? For example... The i3-4010u is running at 1.6 Ghz as far as I remember. Everything is snappy enough, given the horsepower it has. On Cinebench, it scores like a 60 single-thread. Yet it still feels just fine w/ an SSD, so I'm SURE that a lot of perceived performance and snapiness doesn't come from the CPU I suppose. At least in my experience.

 

But then look at this Asus laptop w/ the Pentium 3700. It scores ~40 on cinebench single core, but feels way more than 33% "slower". Not that it's an easy thing to quantify. But it's sort of a "I know it when I feel it" type of thing. But another weird thing I notice is this: The Pentium N3700 is at 1.6 Ghz and boosts to 2.4 Ghz. So why then, does it feel so damn slow in real-world usage? So yeah, I'm aware it's a low-power CPU. So if it's hitting a power limit, I get that's going to slow down. BUT, it's consistently hitting the advertised 2.4 Ghz on all cores. I'm SURE that while the RAM in a budget laptop like this isn't the best, that it's "good enough" to not be the cause of the whole system feeling like it's crawling. I also get that the storage on these speeds is often that eMMC stuff, which (I believe) is usually about as fast as a mechanical hard drive despite being solid-state. 

 

If I assume that it's true that this thing is hitting 2.4 Ghz, and that it performs 33% worse numbers-wise as a 1.6 Ghz i3 series CPU... That could ONLY mean that for whatever reason, the IPC on these particular lines of CPU's, is ATTROCIOUS, and only half as good as the standard "Core" series. My question is, WHY?

 

Are these architectures (Airmont for the 3700 I believe) specifically designed to hit super low power usage, but for some reason have inherently terrible IPC? Because that seems to be the case here. But then why does it even exist in the first place? Is it really cheaper for intel to have a whole dedicated line for this junk, as opposed to the Core-M series? Because THAT is more indicative of what you'd expect out of these kinds of low-powered CPU's that are clocked really low, but still offer respectable performance for what they are. But that doesn't happen with these. Why the hell do they exist then, as opposed to just releasing Core M's to the OEM's that are clocked low? Even the lowest-performing Core M I can find (the 5Y10a) has similar passmark scores, but I GUARANTEE it absolutely wrecks a 3700 in real-world performance in all aspects..

 

I guess this is just a huge rant, but also me trying to wrap my head around all this..

 

 

as said above they have cut down IPC to save on power consumption

[bmichaels556]

1 hour ago, Mira Yurizaki said:

Lower power CPUs are designed to make sacrifices that do cut into IPC. There may be less cache, which eats up a lot of die space. There may be fewer things on the front end, which eat up die space and consume power. Historically out-of-order execution wasn't even on mobile processors until recently because the power needed to feed an OoE system was too much to justify the increased performance.

 

Also note that a lot of cheap PCs, like in the realm of less than $300 USD, aren't going to be using higher speed SSDs. If there is an "SSD", it's likely an eMMC type SSD which for all intents and purposes is like running off a somewhat fast SD card.

 

Also what's "real world usage"? Because for browsing the web to do things like check mail or whatever SNS you use, lower power processors are adequate.

"Real-world usage" as in I guess.. Regardless of what benchmarks and specs say in theory, how does it ACTUALLY perform when using it? And despite how great the N3700 SHOULD be for a low-cost low power consumption laptop in the equation, it still just feels sluggish.

 

Like even opening a new tab and quickly going to Google feels slower on this thing than my old laptop from 2007. Granted, it's totally fine even on that old thing (so long as you don't cap out the RAM). And like I said, I figure at a point, your CPU isn't going to speed up Windows anymore and it's going to start to come down to storage speed, things like that. But it just happens to be noticeable with this laptop, which is why the whole thing perplexes me to be honest.

 

I'll probably be upgrading to something better that doesn't sacrifice battery life sooner rather than later, though so I guess it's not the most relevant thing ever. But I was still curious about the whole thing.

[bmichaels556]

38 minutes ago, astranger200 said:

as said above they have cut down IPC to save on power consumption

Maybe it's just... Well, let's be real. The "average" consumer probably doesn't know their ass from their elbow about what they're shopping for when it comes to CPU's. They go into Walmart or Best Buy, see a "gaming" or "office" PC, and just get what sounds like it'll fit their needs.

 

And so, while I guess it's technically true that this clocks up to 2.4 Ghz, it's sort of fucked up to even market it that way because it doesn't perform how one would expect, if that makes sense? Like... "Oh, this i3 1.6 Ghz. Wow, but that other one is half the price, has four cores, and goes up to 2.4 Ghz! It's GOTTA' be faster and better!"

 

I dunno, I'm just being a pain in the ass I guess.

[astranger200]

1 hour ago, bmichaels556 said:

Maybe it's just... Well, let's be real. The "average" consumer probably doesn't know their ass from their elbow about what they're shopping for when it comes to CPU's. They go into Walmart or Best Buy, see a "gaming" or "office" PC, and just get what sounds like it'll fit their needs.

 

And so, while I guess it's technically true that this clocks up to 2.4 Ghz, it's sort of fucked up to even market it that way because it doesn't perform how one would expect, if that makes sense? Like... "Oh, this i3 1.6 Ghz. Wow, but that other one is half the price, has four cores, and goes up to 2.4 Ghz! It's GOTTA' be faster and better!"

 

I dunno, I'm just being a pain in the ass I guess.

consumers dont realise that clockspeed is more or less irrelevant. its not fucked up to market it by its clock sppeed, because that is a true speed, its just not the be all and end all

[Mira Yurizaki]

13 hours ago, bmichaels556 said:

And so, while I guess it's technically true that this clocks up to 2.4 Ghz, it's sort of fucked up to even market it that way because it doesn't perform how one would expect, if that makes sense? Like... "Oh, this i3 1.6 Ghz. Wow, but that other one is half the price, has four cores, and goes up to 2.4 Ghz! It's GOTTA' be faster and better!"

People would like a simple value to gauge how much performance they'll be getting, but it doesn't really work that way. The only way to compare two different classes of CPUs is to benchmark them.

 

Though I was curious as to what really makes Braswell microarchitecture, which is what the Pentium N3700 uses, different from say the Core microarchitecture from the last half of 2000. So I went to look up some architectural stuff. Like here's the block diagram for Braswell:

 

Compare this to Core:

 

So some key differences I'm seeing, assuming these block diagrams are as accurate as possible

• Braswell can't decode as many instructions as Core
• Braswell can't issue as many instructions to the execution units as Core
• Braswell has fewer options for issuing instructions to the execution units
• You can't see it in the block diagram, but there is less cache. 8KB less for L1 data and 1MB less for L2

In order to make up for the apparent lack of by-design processing power, you can bump up the clock speed. This is what Intel did with the Pentium 4. This is what AMD did with Bulldozer.