Clarification on 640M and 640M LE

Hi there, I am seeking a bit of clarification on the power/potential of mobile graphics cards - as I'm in the market for a new laptop.

The three cards in question are as follows (benchmark ranking listed also):
640M - 85th
635M - 105th
640M LE - 122nd

I've read various things, and was hoping someone with the knowledge could just inform me about each of these cards, and any subvariants of them. Do some come in DDR3 and DDR5? Some can be over clocked, some shouldn't be? How safe is overclocking, is it dependent on the manufacturer of the laptop (different ventilation etc), or is there a general accepted level?

Will appreciate any responses to help me understand thing better Thanks.

Dan

 

640M is the first Kepler card. It comes in variants of DDR3 and GDDR5. The GDDR5 is much more powerful than the DDR3 version and closer in performance to GT-650m. It also overclocks crazy well. I remember at launch 50% overclock was common with a rare few users managing a near-100% overclock, effectively doubling performance and even overcoming GTX-660m. Example here.

635M is a FERMI card. It's barely half as fast as the 640M and is essentially a renamed GT-555m. It's not as cool and doesn't overclock near as well.

640M is a crippled Kepler version of 640M. It comes in DDR3 only and should be a good 30% slower than 640M at stock settings. It won't overclock anywhere near as good either. Another issue with this card is that there is also a rebranded GT555 Fermi version of it as well, which is even worse.

tl;dr: 640M is pretty awesome especially in an ultraportable, providing it runs at GDDR5. The others are pretty meh.

 

Thank you sangemaru, that helps a lot. I did read it all don't worry. The third paragraph I know you're referring LE variant.

Can I ask a basic question? Am I right in saying there are 3 varieties of memory type, DDR3, DDR5, and GDDR5? Or is GDDR just a term for DDR that's on graphics processors?

And just to finally confirm, if it says LE - it's going to be the poorer 640m? I find it hard to find many without the LE

 

Correct.

GDDR3 is based from DDR2 (today this is the low end memory, although more commonly nowadays DDR3 is used instead in low-mid end GPUs)
GDDR4 is also based on DDR2 (rare, was only used in a few specific GPU models from a few years ago)
GDDR5 is based from DDR3 (DDR3 doubled bandwidth of DDR2 - that is why GDDR5 is that much faster, also runs at higher clocks)

 

Thanks Cakefish.

Another question - can you get card models with either DDR types? For example, the 650M comes in DDR3 or DDR5 (if I'm not mistaken). I often get excited when I find a deal with a 650, but then find it's DDR3 and worry it won't be so good. The benchmark lists just list 650M, but doesn't say whether it's DDR3 or DDR5.

 

the 640 LE seen in the Sony S13/S15 has seen OC up to 650m levels (nearly doubled clocks) which is fairly impressive.

the Kepler 640 LE should be a little faster then a 635m at stock clocks though. it also uses less power and produces significantly less heat.

 

How do you know which LE you're buying? Do you just trust if it's from Sony then it's a better version?

 

your best bet is to check out the owners lounges for any laptops you are interested in... they normally will have screen shots of CPU-z which will list info on the GPU. Some manufacterurs will also just tell you straight up if its a kepler or fermi.

if you can get the shader core count that is also a giveaway since the kepler has something like 384 while the fermi has 96-144 cores.

 

650M DDR3 is faster than 640M GDDR5. That is why it is numbered higher!

 

Yeah I guess it makes sense to always have the newer model perform better than the previous.

The other part of that question is still unanswered though: Does the 650M (for example) come in both DDR3 and DDR5? Do certain cards get made in both varieties?

 

Yes. For example: the asus n56vz has a 650m ddr3 gpu while the ideapad y500/y400, alienware m14x, mbpr,... have a 650m with ddr5 memory.

 

So I guess it's always best not to assume its the DDR5 one, and check with who you're buying from what version it is.

The bit that confuses me a bit though is the benchmarks never list DDR3 or DDR5 separately. Guess they usually benchmark the best version (DDR5).

 

GDDR5 makes the biggest difference at higher resolutions. It's been shown that the Clevo W110ER with GT 650m with DDR3 vRAM is as fast or faster than the GT 650m with GDDR5 vRAM in the Alienware M14x at 1366x768 or 720p. But once you get to 1600x900 or higher the DDR3 limited bandwidth will cause it to suffer, while the GDDR5 version will manage that higher resolution without as much drop in FPS. So if your laptop has 1366x768 screen, and you don't plan on gaming on an external monitor, DDR3 is just fine.

 

Music to my ears (or eyes?)!

Also the extra high core clock of the DDR3 version helps it to keep up with the GDDR5 version.

 

Awesome, appreciate the information. So in summary, if you're not getting a high res screen, and just a standard 768 res that many laptops ship with - then DDR3 isn't such a step down from a DDR5 equivalent. But, if you have a higher res screen, or wish to use a higher res on an external monitor, then the DDR5 will outperform significantly.

Do you mind explaining the clock speed stuff now I seem to get the DDR stuff a bit more? To simplify, it's how fast the GPU can process each operations? So the bigger the number, the more operations per second it can process? So some come at a certain clock speed, meaning they can perform X amount of calculations per second. You can overclock this barrier to force it to have more "processing calculations" per second, but doing so may risk the GPU overheating as it wasn't designed to work at that pace?

 

gddr3 = ddr3 (tweaked for graphics loads - read higher latencies higher speed)
gddr4 = ddr3 (power tweaks that failed)
GDDR5 = GDDR5 (quad data rate)

 

There are GDDR5 versions of GT 640M too
Dell have GDDR5 on some XPS models, Samsung on some of theirs and Acer on their Aspire M5

Its a mess

 

yea Nvidia likes to make things confu... ahem give you lots of options!

 

Could anyone please help me understand about the clock speeds and their significance, I asked above about it?

Also, the significance of 1GB vs 2GB on a card?

 

Performance of gpu's is really hard to estimate by the clock speed and amount memory. The same gpu with higher clocks will indeed do more in less time, making it faster. But there are also other very important factors, like the architecture. This is the same for cpu's. For example: an ivy bridge i7 3610qm cpu clocked at 2,5 gigahertz will outperform a 2610qm sandy bridge i7 clocked at 3 gigahertz because of the worse architecture on the sandy bridge cpu. Clock rates are not very good for comparing gpu's.

The best thing to do to rate a video card is to look at the model number. The first number tells what generation it is both with nvidia and amd. 6xx is the latest nvidia generation, 7xxx from amd (8xxx generation will be available the coming weeks). The second number, between 1 and 9 describes the performance within the generation. 1 is slow, entry level 9 is the very high end. Amd adds a third number, usually 3, 5, 7 or 9 to describe the performance within that category. An m at the end explains that it is the mobile version of the card but it is mostly significantly slower than the desktop graphics card with the same number. For example: the amd radeon hd 7970m is based upon the desktop radeon hd 7870.

So in general it is best to see at the model number and benchmarks. Clock speeds, memory, shader cores, tdp,... are not that representative.

I'm sorry if you already knew all that, not trying to make you look dumb.

As for your question about memory: again, not representative at all. It is best to go with the highest rated card instead of going for the one with the most video memory. 1 gb vs 2gb only makes a difference if you are using external monitors with very big resolutions. In general 1 gb will be just fine for normal gaming. Most people don't know this. They buy something with 2gb of video memory because it's more than 1 and think they have a good graphics card. An nvidia 630m with 2 gb will be significantly slower than a 650m with 1gb or even 512mb of video ram.

I hope this helps you a little. If you wonder what mobile gpu is the fastest, just check out notebookcheck and you'll see. No need to compare clockspeeds, bandwidth, cuda cores,...

 

Hey, firstly - thanks SO much for the time you took to write that big amount of information. It was all valuable. Some I knew, but not in as much detail as you've outlined. The reason I was asking however wasn't just to gauge which graphics card is the best.

It was more for understanding if you have a 650m 1GB and 2GB, what exactly does that extra GB provide? When does the 1GB become a form of throttle?

And with regards to understanding clockspeeds, one of the reasons I was curious was because I wanted to understand what I'm doing when I go to overclock. When overclocking, you can boost the clock speed, as well as the memory speed (I'm guessing this is the speed of the GDDR5 memory). So you're essentially increasing how many calculations it can perform per unit of time, but it will also increase the temperature generated. And with the GPU memory overclocking, what is that actually doing?

I guess I'm a little curious about all this, as when researching the 6 series nividia cards, I've seen that a few of them are the exact same card just with a different clock speed. I'm trying to understand what limits the clock speed exactly, like how can a clock speed of one card be 800 say, but then the same chip that's sold at 500 can't be clocked to 800 safely? Sorry if my lack of knowledge makes for a confusingly worded question!!

 

You're welcome

The extra 1 gb won't really matter when you're not using a screen with a very high resolution. Your gpu will most of the time start struggling to keep up way before you run out of video memory, definitely with a gpu that is not really high end.

Overclocking, like you said, basically lets your gpu, video ram, cpu or ram do more in one second than it normally would, thus making your components work faster resulting in better performance. This however always generates extra heat because it uses more power.

That's why some cards that basically look the same are clocked lower than others. They can't handle the heat very well, produce more heat at the same clocks due to different architecture or they are made for laptops that do not have a very good cooling system, like realy thin laptops so they must not produce too much heat.

 

Sweet, thanks that makes sense.

This might not be the best place to ask, but you seem to have a good knowledge about this stuff so I might leech you a little more In regards to overclocking, what would you recommend? I will google when I receive my laptop specific values for my card based on peoples feedback etc, but I just mean in terms of what would you overclock? Each of the GPU, Vram, CPU, and normal RAM? Or is it not really worth doing it all? Is there a risk of damaging components (realistically), or will the machine crash/shut down to prevent potential damage? I won't hold you to your word btw and hold you accountable if I try in future and it explodes!

 

I have spent a lot of time researching what laptop I want but I'm sure a lot of members here have far more knowledge and experience.

I have little to no experience in laptop overclocking myself (for now) only from reading a lot on the internet. If I were you I wouldn't touch the ram and cpu because they generally are more than fast enough for gaming and normal usage. Yes you can damage your components by overclocking too much, you should always do it a little at a time, monitor your temps and do stress tests to check stability. Your laptop will indeed shut down if it gets too hot but I really wouldn't recommend getting to that point.

If you decide to overclock you should read threads like the owners lounge of your laptop. They can tell you what clocks are stable, safe, how much it benefits and also how to do it because it is not that easy with most laptops. Sometimes clocks are locked and need some extra work apart from just setting a higher clock speed.