What difference does the memory make?

[transylvanic]

I am wondering what sort of performance improvement comes about from additional memory. Last time I was deeply interested in gfx cards, the new 512MB cards were coming out and everyone was saying how redundant all that onboard memory is. Now that's pretty much standard, but do games use it?

For example, I have a 3650 which goes like a dead donkey, but it has 512MB. I understand the 128/256bits distinction matters, but I don't know why. I understand more memory is valuable on a higher end card, but again don't know why.

Any illumination will be appreciated. And for a more specific scenario, what is the performance difference between a 512MB and 1GB 4850 or 4830?

[aidanjt]

The same claims of needless redundancy still applies.

You'll only need 1GB to drive a 30" monitor. Even at that, there's a crapload of free memory to spare.

If you have a 24" monitor, 512MB is plenty. Aim for a faster GPU and greater bit width over memory capacity.

[Zak33]

trans, its a very VERY good question that you raise dear chap, and I'm very interested in working out how to explain stuff , so here goes

Ready?

You are playing a 3d game in real life, in your back garden.
Imagine that all the 3d structures for your game are stored in a garage at the front of your house, and the access to these structures, being screwed together, and put away when not needed, and brought to the garage door ready for use, is being done by a GPU. A Graphics Processor Unit. This poor bloke has a lot to do, but needs helpers to take the stuff to the rear garden.

You are "playing" the game in the back garden.

People have to run to the garage, grab a 3d structure (when the GPU has it ready), and bring it down the side path, through the gate, to lay it out for you to "play " on.

This happens lots of times per second.

The speed and power of the GPU is the bloke in the garages ability to make and send the blocks, slopes, textures etc.
The SPEED of the memory chips is equivalent to the speed of loads of blokes running back and forth

The 128bit/ 256 bit memory controller is the WIDTH of the path down the side of your house determines how many of these 3d objects can move at any one time, and even HOW MANY paths go down the side of your house. If you had a path down BOTH sides and even one through the front door, through the hall and out through the back door, it would help. Thats memory controller bandwidth

So, with respect to this, it doesn't matter HOW BIG your garage is, so long as it can hold all the 3d structures that you need for the size of your garden.

Your garden is your monitor. If you have up to about a 22" monitor, your "garage" doesnt really need to be much bigger than 512mb

I'ts the speed that it goes that helps the most.
The CORE speed on the Graphics Processor Unit, the memory band width and the memory controller all working together.

I think that's ok... read it through a few times and ask away.

[kalniel]

And with DDR5 each bloke can carry twice the stuff of DDR1/2/3/4 (which is itself twice that of SDR), so even if you have the same width path and they're moving the same speed, more data is being transfered.

[Teamsreth]

I tell you what, I have seen and heard many different discussions about this sort of thing, and that, BY FAR, was the best explanation I have ever seen.

So, up to 22-24 inch, it's not how much stuff you can store, it's how quickly you can shift the stuff you have?

[kalniel]

So, up to 22-24 inch, it's not how much stuff you can store, it's how quickly you can shift the stuff you have?

As long as you can store enough stuff, then yes. But that's always the case with memory size - you only need as much as will cope with what you're trying to store - beyond that doesn't usually give any performance increase (until you find a use for extra storage).

[badass]

The same claims of needless redundancy still applies.

You'll only need 1GB to drive a 30" monitor. Even at that, there's a crapload of free memory to spare.

If you have a 24" monitor, 512MB is plenty. Aim for a faster GPU and greater bit width over memory capacity.

Today that's true. However there are likely to be titles in the next year or 2 that will run fine on say an HD4870 1GB and awfully on a 512MB one.
I have a Geforce 8800 GTS 320MB because everyone said it was as fast as the 640 MB one at my resolution, but at some parts of F.E.A.R. and a copule of other games, it is running over 60 FPS then drops to 1-2 FPS because it doesn't have enough video memory.
TBH I'd ratehr have had 512MB or just got the 640MB 8800 GTS for £30 more.

[CAT-THE-FIFTH]

I think you need to make a distinction between lower end graphics cards and higher end graphics cards!!

Also what about AA then??

Also in the near future games are going to need more video RAM anyway and at least a higher graphics card has the processing power to make use of it!!

Look at the difference between the HD4870 1gb and 512mb even in games like Crysis and Farcry 2 for example at 1680x1050 with AA enabled!

[aidanjt]

Today that's true. However there are likely to be titles in the next year or 2 that will run fine on say an HD4870 1GB and awfully on a 512MB one.
I have a Geforce 8800 GTS 320MB because everyone said it was as fast as the 640 MB one at my resolution, but at some parts of F.E.A.R. and a copule of other games, it is running over 60 FPS then drops to 1-2 FPS because it doesn't have enough video memory.
TBH I'd ratehr have had 512MB or just got the 640MB 8800 GTS for £30 more.

That doesn't reflect my own experiences with the same card. Which is still capable of powering my 24" monitor with any game I've thrown at it.

[aidanjt]

I think you need to make a distinction between lower end graphics cards and higher end graphics cards!!

Also what about AA then??

Also in the near future games are going to need more video RAM anyway and at least a higher graphics card has the processing power to make use of it!!

Look at the difference between the HD4870 1gb and 512mb even in games like Crysis and Farcry 2 for example at 1680x1050 with AA enabled!

Then don't use anti-aliasing? Aside from e-peni points, it's useless with modern monitors anyway.

[transylvanic]

Thanks fellas. That is enlightening. So when did the move to 256-bit pathways happen? When should we expect the jump to 512?

I kinda figure from all this, if a dude gets a smaller, but faster, memory package, he can deal with memory shortages by going to lesser detail settings. On the other hand, if you get a slowcoach with memory, you can't get the latter to fix the former.

I'm so bitter at getting this 3650 now.. it was cheap and I was just getting something with a DVI output on a new build, but still. My X800XT from 4 years ago was/is better.

It's a funny one because playing prince of persia I get the same rubbish frame rates at 800x600 as I do at 1680x1050. So yea, I reckon you've confirmed my belief that memory is something you need to maintain frame rates at higher res, but it wont help when you've got a slow gpu.

[CAT-THE-FIFTH]

Then don't use anti-aliasing? Aside from e-peni points, it's useless with modern monitors anyway.

Sorry to say this but you are not entirely correct as there are some games that can make use of the extra RAM and also if you are buying a high end card then why not use AA??

http://www.bit-tech.net/hardware/gra...olden-sample/4

http://www.guru3d.com/article/amd-at...024mb-review/8

http://techreport.com/articles.x/15651/9

If you do not care about AA or are not playing games at resolutions which will not make use of the extra RAM then a 512mb card will be enough. However to say that no games currently make use of the extra RAM is incorrect.


HD4870 1gb for £184:

http://www.overclockers.co.uk/showpr...odid=GX-120-XF

http://www.novatech.co.uk/novatech/s...html?nov-48701

It is also not clocked any slower than a 512mb card too. Whether this is worth the extra £20 on top of the price of a 512mb HD4870 is dependent on what games you play.

[Zak33]

I tell you what, I have seen and heard many different discussions about this sort of thing, and that, BY FAR, was the best explanation I have ever seen.

So, up to 22-24 inch, it's not how much stuff you can store, it's how quickly you can shift the stuff you have?

good, glad you liked it.

[Salazaar]

So when did the move to 256-bit pathways happen? When should we expect the jump to 512?

I remember my 9800XT (ATI, not Nvidia) had a 256bit bus. It's one of the things which made that card so special.

[Pob255]

great description Zak

@transylvanic, I'm not surprised you're disappointed with the 3650 coming from a x800xt
You gone from a high end older series card to a low end newer series card, so it'll be trying to do more with equal or less power.
As Salzaar said 256bit bus happened a while ago, nvidia did take the next step with 320bit on the old 8800gts 320mb & 640mb and 384bit with the 8800gtx and ultra, however that step was very short lived as the memory&controller was simply too expensive and pushed the prices of thoes cards up quite high.
They then went back to 256bit on most of the 9 series cards and have again stepped out into 448bit on gtx260&295 and 512bit on the gtx280&285.

ATi has stuck with 256bit but have but have moved up to gddr4 and 5 on there top end cards.

Mid and especially low range cards will not just be slower clock speeds but fewer streams/pipes and smaller memory bandwidth.

Many companies seem to stick large amounts of memory on low to mid ranged cards that simply don't have enough power and bandwidth to use it.
From Zak's explination, it's like there's one man to build stuff and he takes constant tea breaks, only one man to cart the stuff to the back garden and he's got a gammie leg.
So there's really no point in replacing the front garrage with a warehouse.

One thing to note here is games are getting far bigger for graphics memory demands, not only is the polygon count going up, but so is the complexity of the effects and texture size.
The texture size is a biggy because of the power of two, which means each step up in size make the the size 4 times bigger, (eg 512x512 to 1024x1024)
Some of this is being worked around by new texture formats but these in turn create new issues and can end up using more memory but reduce the gpu load.

[jackvdbuk]

I remember my 9800XT (ATI, not Nvidia) had a 256bit bus. It's one of the things which made that card so special.

ahh good card! remember my first gpu was a 9800 pro and tried to flash it to xt speeds but woulndt work becuase i had the wrong chip (no temperature monitoring thing either on that card)