Can someone explain the meaning of 32-bit and 64-bit as they relate to video cards?

[Ken90630]

Hi, All,

Yes, I'm embarrassed to be asking this after all this time, but I don't know, so here goes.

When looking at video card specs, I notice they typically come in either 32-bit or 64-bit versions (and occasionally 128-bit versions). What does this spec pertain to? And what advantage does a 64-bit card have over a 32-bit one? In other words, with what applications would a person notice a difference?

Lastly, if one is using a 64-bit operating system, is it advantageous to have a 64-bit video card or are they irrelevant to each other?

 

[3DVagabond]

What card(s) and which specification are you looking at? I have a feeling that you are talking the memory bus size. In which case it's one of the variables, along with memory speed (MHz) and type (GDDR3, GDDR5, etc.) that determines how fast the memory can process information.

 

[brybir]

Hi, All,

Yes, I'm embarrassed to be asking this after all this time, but I don't know, so here goes.

When looking at video card specs, I notice they typically come in either 32-bit or 64-bit versions (and occasionally 128-bit versions). What does this spec pertain to? Is it color depth (I think I might have read that?), and if so, what advantage does a 64-bit card have over a 32-bit one? In other words, with what applications would a person notice a difference?

Lastly, if one is using a 64-bit operating system, is it advantageous to have a 64-bit video card or are they irrelevant to each other?

Usually the concept of a "32-bit" or "64-bit" or higher refers to the width of a data bus between two components. In video cards the predominant reference is to the link between the video card memory and other components. This connection is a data bus and is described by both the number of "bits" and a frequency that it operates on.

I always think of databus connections as a highway. The number of bits is the number of lanes and the frequency is how fast the cars can move on the highway. So, if you have a video card memory bus that is 128-bit, you have 128 lanes of traffic. If that video card memory bus operates at 1000mhz, then you have 128 lanes of cars moving at 1000mhz speed.

So, in terms of video cards, you can either increase the speedof the lanes to make all the cars move faster, or you can add extra lanes at the same speed. Either way, more cars are moving across the highway. You can also do some combination of both.


In terms of video cards, if you have a card like the Radeon 6850 that has memory frequencies of 5000mhz attached to a 128-bit bus, the most information that can move across that bus is about 76GB of information per second. Now, if you use that same card, with the same memory, at the same speed, but attach the memory to a 256-bit databus, you are effectively doubling the number of "lanes" and you can then move about 152GB of data per second. So, if you run an application or game that can utilize more than 76GB of data per second, then the databus width will limit the ability of the card to run at full throttle.

There are a lot of other little technical issues, but I think that is generally what the bit references are you are talking about.

 

[Arkadrel]

@Ken90630

You probably have ALOT of things all mixed up.
(ei. the CPU/OS, driver versions of software for GPUs to match OS's, Colour depts, and GPU bus widths)

You should take this to the CPU section.

 

[Ken90630]

What card(s) and which specification are you looking at? I have a feeling that you are talking the memory bus size. In which case it's one of the variables, along with memory speed (MHz) and type (GDDR3, GDDR5, etc.) that determines how fast the memory can process information.

Cards like this and others (all the PCI-E cards I'm looking at are presented the same way, in terms of specs listed, on Newegg's site):

http://www.newegg.com/Product/Produc...82E16814130607

In that example, I'm referring to the "64-bit" spec and what it pertains to.

 

[Ken90630]

@Ken90630

You probably have ALOT of things all mixed up.
(ei. the CPU/OS, driver versions of software for GPUs to match OS's, Colour depts, and GPU bus widths)

You should take this to the CPU section.

No, I don't think I've got too much mixed up. I'm reasonably well-versed on computer-related specs, except this one related to video cards. It's definitely not a CPU-related issue.

 

[Zorander]

Cards like this and others (all the PCI-E cards I'm looking at are presented the same way, in terms of specs listed, on Newegg's site):

http://www.newegg.com/Product/Produc...82E16814130607

In that example, I'm referring to the "64-bit" spec and what it pertains to.

That's the memory/bus size, according to official spec.

 

[DominionSeraph]

I'll make it simple for ya' Ken: Basically, nothing they tell you -- MHz, cores, bus size, memory speed -- is useful. You need to use benchmarks.

If you're looking for something that can game, the lowest I'd suggest are the 9600GT, GT 240, 5670, and 6570/6670. (Incidentally, all of those should work with an OEM power supply. I'm rocking a 9600GT in a Dimension E521)

If you have a power supply with a little more wattage, you can find good deals on GTS 250, 9800GT, and 4870. I believe TigerDirect has a GTS 250 for $50 after rebate which is pretty darned good given its performance.

If you only need 2D... hell, anything will work.

e: I see by your other thread you just need a basic 2d card. 5450 or GT210 is all you need.

 

[-Slacker-]

I'll make it simple for ya' Ken: Basically, nothing they tell you -- MHz, cores, bus size, memory speed -- is useful. You need to use benchmarks.

^^^^^^

Pretty much this. If you want to know which card is faster, there's really no shortcut, you'll just have to stalk tech forums like us nerds and wait for benchmarks.

 

[RampantAndroid]

It just means the bus between the RAM and the GPU is a 64bit wide bus. They're up to what, 512bit buses?

 

[3DVagabond]

Cards like this and others (all the PCI-E cards I'm looking at are presented the same way, in terms of specs listed, on Newegg's site):

http://www.newegg.com/Product/Produc...82E16814130607

In that example, I'm referring to the "64-bit" spec and what it pertains to.

Yes. It's the memory bus size. That along with the memory speed and type determines the overall memory processing power. It's generally given in GB/S. Making it too small and you end up with a memory bottleneck. Too big and you are paying for a more expensive memory bus than needed.

The gtx 460, for example, came with a 256bit mem bus. They released another model with 192bit mem bus and it was slower. (Is anyone actually buying this card anymore? Just looked at Newegg and talk about price gouging! ) Graphics card overall performance is a combination of many specs. They have to be in balance. Too much in one area is no good because it will just be bottle necked by the rest of the card. You'll be paying more for nothing.

 

[Ken90630]

Thanks, everyone, for the replies.

So since I now know that the 32-bit and 64-bit specs relate to the memory bus size, what would be some examples of why I would want/need a card with a 64-bit bus over one with a 32-bit bus? Are the 64-bit bus cards primarily geared towards gamers, or would more general use like Photoshop or watching high-def video also benefit from having a 64-bit bus on the card?

 

[Ferazel]

I won't necessarily repeat what was said (since it's correct), but I just wanted to say thanks for asking a serious question and not being a troll about it. Maybe I hang around a lot of bad forums, but being big enough to admit you don't know what something means and want to know is inspiring. ()

 

[Zorander]

Thanks, everyone, for the replies.

So since I now know that the 32-bit and 64-bit specs relate to the memory bus size, what would be some examples of why I would want/need a card with a 64-bit bus over one with a 32-bit bus? Are the 64-bit bus cards primarily geared towards gamers, or would more general use like Photoshop or watching high-def video also benefit from having a 64-bit bus on the card?

DominionSeraph's has already answered your question.

 

[Ken90630]

DominionSeraph's has already answered your question.

Mmm, not really. While I appreciate his reply, I'm still not clear on what the specific advantage is of having a card with a 64-bit bus vs. one with a 32-bit bus. I understand they're part of the larger picture of inter-related specs, and as such aren't determinative of performance by themselves, but I still don't know when, for example, a user would specifically look for a card with a 64-bit bus over a 32-bit one. In other words, if you were shopping for a new video card, when/why might you say, "This card looks good, but it only has a 32-bit bus. I need one with a 64-bit bus."

 

[destrekor]

Thanks, everyone, for the replies.

So since I now know that the 32-bit and 64-bit specs relate to the memory bus size, what would be some examples of why I would want/need a card with a 64-bit bus over one with a 32-bit bus? Are the 64-bit bus cards primarily geared towards gamers, or would more general use like Photoshop or watching high-def video also benefit from having a 64-bit bus on the card?

Really, what it means is anything that is video-intensive, will perform better as you move to a wider memory bus (all other specs being equal).

I do have to say, even a 64bit bus would be terrible for intensive gaming (think: higher/highest settings in most video games, though this is a gross oversimplification). Most recent-generation cards between mid-performance and top-end have over 256bit memory buses, even 384 and 512bit.

[You can also have a 512bit memory bus on a card that happens to perform terribly for games, if the manufacturers coupled that with low-end specs.]

As for needs, well... hard to really say when a specific bus width is better than another.

If you want to do GPU-based video acceleration, a wider bus, like 128bit, will certainly perform better than a 32bit. Anything 3D, and I'd pretty much say you want a minimum of 128bit - gunning for quality settings with recent games, nothing less than 256bit... and that's coupled with a beefier card anyhow.

And yes, intensive use of Photoshop, and more appropriately, any visual-media editor, would be best coupled with a wider bus. Video-editing, GPU-based video rendering, 3D modeling software, and the like... would perform better on a wider bus.

Most importantly, do consider this: you won't see many cards of similar-specs with widely varying bus widths. And there are also architectural differences between GPU generations, where the new-generation top-end card is released with a bus width that is less than the previous model. And it still performs better in every possible way.

Most often, the architecture/design is more important than the specs you are shown.
So, as others stated, it is best to shop by using benchmarks as a reference, than by worrying over specs.

It really is hard to say application Z needs a specific bus and is thus impossible to recommend any video card with a bus less than X.
Because such apps could perform terribly on a card with a 128bit bus, and then turn around and perform beautifully on a card with a 64bit bus.

Some benchmark sites even go and use such photo/video/modeling suites in their GPU benches.

 

[Zorander]

Mmm, not really. While I appreciate his reply, I'm still not clear on what the specific advantage is of having a card with a 64-bit bus vs. one with a 32-bit bus. I understand they're part of the larger picture of inter-related specs, and as such aren't determinative of performance by themselves, but I still don't know when, for example, a user would specifically look for a card with a 64-bit bus over a 32-bit one. In other words, if you were shopping for a new video card, when/why might you say, "This card looks good, but it only has a 32-bit bus. I need one with a 64-bit bus."

You need to look beyond mere specs (bus width, in this instance), as Dominion previously advised.

I looked around briefly and there is a trend where the memory bus width scales up with the 'class' of the GPU chip. Low-end chips tend to be paired with 32- to 64-bit bus, midrange 128-bit and high-end 256- to 512-bit. You can bet a more expensive card will beat a lesser one from the same family. It's however not a useful way of determining performance. Way too generalised.

Benchmarks will tell you in far more specific way how a particular card will perform in particular tasks.

 

[destrekor]

You need to look beyond mere specs (bus width, in this instance), as Dominion previously advised.

I looked around briefly and there is a trend where the memory bus width scales up with the 'class' of the GPU chip. Low-end chips tend to be paired with 32- to 64-bit bus, midrange 128-bit and high-end 256- to 512-bit. You can bet a more expensive card will beat a lesser one from the same family. It's however not a useful way of determining performance. Way too generalised.

Benchmarks will tell you in far more specific way how a particular card will perform in particular tasks.

Because in the end, the whole market is already established simply by GPUs - some tweaks by manufacturers, but they don't stray far from reference, sticking to reference more often than not.

The reference designs tend to incorporate the most effective bus width with whatever that specific GPU model is capable of utilizing; i.e. if the processing capability and flow of data cannot saturate a given throughput, why give it more throughput? And the reference designs are basically all about the most effective performance possible from that specific core piece of silicon at it's heart (GPU itself, not the card).

 

[RampantAndroid]

Mmm, not really. While I appreciate his reply, I'm still not clear on what the specific advantage is of having a card with a 64-bit bus vs. one with a 32-bit bus. I understand they're part of the larger picture of inter-related specs, and as such aren't determinative of performance by themselves, but I still don't know when, for example, a user would specifically look for a card with a 64-bit bus over a 32-bit one. In other words, if you were shopping for a new video card, when/why might you say, "This card looks good, but it only has a 32-bit bus. I need one with a 64-bit bus."

We can talk numbers and theoretical speeds all day, but a larger bus combined with slow RAM may be slower than a smaller bus with larger ram.

Really, the bus is a pipe. The bit width is the diameter. More bits means more data can travel across the bus at the same time. The advantage is that it takes a shorter period of time to pull or push data to/from the VRAM.

This differs from address size (which is what you see with 32bit and 64bit CPUs and operating systems) in that the count is how large the address can be. A 32bit operating system/CPU can only access 4,294,967,295 bytes of memory. A 64bit OS/CPU can access 18446744073709551616 bytes (I think I have my math right.)

Make any sense?

 

[Red Hawk]

I'll make it simple for ya' Ken: Basically, nothing they tell you -- MHz, cores, bus size, memory speed -- is useful. You need to use benchmarks.

Hm, not necessarily. They're still useful within the same generation of graphics cards by a single manufacturer. Without the benchmarks of a Radeon HD 5850, you can still ascertain that the Radeon HD 5670 is a good deal slower.

 

[LiuKangBakinPie]

VRAM data bus width arranged as independent partitions of xxx pins each. For example Slimer uses a VRAM data bus width of 384-pins, arranged as six independent partitions of 64 pins each. Each partition supports GDDR5, and exclusively owns two 32-bit DRAMs.

Nvidia and Amd connect their memories differently so the bigger bus between the two is not always better. Amd had normally the performance advantage with the memory connection and performance where Nvidia had the better Processing unit and shader performance

 

[LiuKangBakinPie]

Hm, not necessarily. They're still useful within the same generation of graphics cards by a single manufacturer. Without the benchmarks of a Radeon HD 5850, you can still ascertain that the Radeon HD 5670 is a good deal slower.

http://www.realworldtech.com/page.cfm?ArticleID=RWT041111203710

 

[PrincessFrosty]

In general, the terms "bits" refers to the length or accuracy of a number, the greater the "bits" the larger or more accurate the number can be.

In terms of graphics hardware if you read 64bit for example it could refer to a number of different things, if you're talking about hardware specifications it tends to refer to the width of the Memory bus which is the data transport between the video memory and the other components on the video card such as the GPU.

The memory bus is partly in responsible for the total memory bandwidth of the card which is an important performance metric as memory bandwidth can be a limitation of a video card, the memory bandwidth is actually the width of the bus multiplied by the frequency at which the bus operates so the width or "bit" value doesn't tell the whole story you ideally need to know the memory speed as well to make a judgement on performance.

In general graphics it can refer to other things such as colour depth/accuracy or computational accuracy, basically anything that can be stored as a number can be given to a "bit" accuracy.

 

[Concillian]

In other words, if you were shopping for a new video card, when/why might you say, "This card looks good, but it only has a 32-bit bus. I need one with a 64-bit bus."

The width of the data bus is not the important parameter here.

It is a component to the total memory bandwidth, and that's important, but the REAL important thing is the GPU itself.

How much memory bandwidth is enough?
The only answer to this is "enough".

That sounds confusing, but think of it like a freeway. If the freeway is wide enough to handle all the cars at the speed limit, then it's "wide enough". If there is some slowdown, then it could use a lane or two added to add throughput. What is enough for a freeway between Topeka and Omaha would not be enough if the same number of lanes were put between Burbank and Anaheim.

The GPU that the memory is attached to and what you're doing with that GPU determines how much traffic there is and how much bandwidth is "enough"

If you're just doing Facebook and Google and Photoshop and Excel? the lowest available GPU and lowest available memory bandwidth is "enough"
If you're gaming on a 30" monitor at the highest quality settings with $500+ GPUs? The highest available memory bandwidth is "NOT enough"

Generally what you see is bandwidth increases with GPU specs and price.
- Cards that perform extremely poorly in gaming = 64 bit / low bandwidth
- Entry level gaming cards = 128 bit DDR3
- Low end gaming cards = 128 bit GDDR5
- Midrange gaming cards = 192-256 bit GDDR5
- High end gaming cards = 256-384 bit GDDR5

If you are not gaming, then memory bus width is not at all important.
If you are gaming, then buy based on the GPU. Memory bandwidth will generally follow along with the GPU without having to worry about it. Selecting the GPU is the important thing, it has the largest impact, and the designers of the card will pair a serious gaming GPU with "enough" bandwidth that it is not a significant limitation.

Occasionally you'll find a card that is totally neutered by too low memory bandwidth, but you don't see that nearly as often now as you did 5+ years ago. For the most part you don't have to worry about selecting "the right" memory bandwidth. You need to select "the right" GPU, and the memory bandwidth that goes along with that GPU is what it is.

 

[GaiaHunter]

In terms of video cards, if you have a card like the Radeon 6850 that has memory frequencies of 5000mhz attached to a 128-bit bus, the most information that can move across that bus is about 76GB of information per second.

Hey!

6850 256-bits.

To the OP - the GPu stores in its memory loads of data from textures, the image displayed, the result of its calculations, etc.

Bandwidth is the speed at which the gpu can store stuff on the memory and read what is there.

Think of it in a similar way to you downloading a program. The faster you download it the faster you can use it. Also maybe you can download 2 programs at the same time instead of just 1.

That is the advantage of higher bandwidth. More calculations need more information, better graphics need bigger textures, etc.

But bus size is only 1 factor of bandwidth.

Speed and type of memory are also important and contribute to bandwidth.

And then a GPU needs to have processing power to make use of all the information it can store and read from the memory or it won't matter.