When does a 128bit bus become an issue?

[Hey Zeus]

I'm looking at a new graphics card and i want to go ATI but the whole 128bit bus is kinda turning me off. When does it become an issue? how much better is 256?

 

[crisium]

Always. Really. 5770 would be faster than a 4890 if it weren't an issue. But it isn't, and even at the lowliest resolution the 4890 is virtually always faster.

1200MHz at 128-bit is equal to 600MHz 256-bit. So core/mem the 4870 is effectively 750/900 and the 5770 is 850/600. The extra bit on the clock usually isn't enough to make up for the memory hit. If you use 256-bit DDR5 as your main idea, then just divide 128-bit in half.

128-bit DDR5 is = 256-bit DDR3, btw.

I think it's really just a matter of benchmarks. I suggest reading benchmarks with minimum FPS, as 128-bit seems to have a bit of an issue there. As long as you see benchmarks and know what you'll getting, it shouldn't matter what bit it is. General rule of thumb, 5770 is a little slower than a 4870 and GTX 260. You probably already know this, so I'm just a bit confused as to what you want to know.

 

[Hey Zeus]

Always. Really. 5770 would be faster than a 4890 if it weren't an issue. But it isn't, and even at the lowliest resolution the 4890 is virtually always faster.

I think it's really just a matter of benchmarks. I suggest reading benchmarks with minimum FPS, as 128-bit seems to have a bit of an issue there. As long as you see benchmarks and know what you'll getting, it shouldn't matter what bit it is. General rule of thumb, 5770 is a little slower than a 4870 and GTX 260. You probably already know this, so I'm just a bit confused as to what you want to know.

1200MHz at 128-bit is equal to 600MHz 256-bit. So core/mem the 4870 is effectively 750/900 and the 5770 is 850/600. The extra bit on the clock usually isn't enough to make up for the hit. If you use 256-bit DDR5 as your main idea, then just divide 128-bit in half.

I was hoping you'd talk me into liking 128bit but i kinda feel cheap even thinking about it. One of the reasons why im leaning towards a 4890 or a pair of 250's in SLI

 

[Lonyo]

A 128bit bus becomes an issue when it results in lower overall memory bandwidth.
The width of the bus itself on its own is meaningless. A 128-bit bus with 4GHz memory will have the same bandwidth as a 256-bit bus with 2GHz memory.

The main thing to look at is overall performance, since the number of bits in the memory bus alone is pretty meaningless, and even memory bandwidth alone won't tell you a huge amount.

 

[happy medium]

A 128bit bus becomes an issue when it results in lower overall memory bandwidth.
The width of the bus itself on its own is meaningless. A 128-bit bus with 4GHz memory will have the same bandwidth as a 256-bit bus with 2GHz memory.

The main thing to look at is overall performance, since the number of bits in the memory bus alone is pretty meaningless, and even memory bandwidth alone won't tell you a huge amount.

So how about the gtx 260 448 bit gddr3 bandwidth.
How do you do the math?
Thanks

The gts 250's banwidth is 70gb. How does that compare to say my 128 bit hd5750 at 1375 (5500) memory?

 

[Lonyo]

So how about the gtx 260 448 bit gddr3 bandwidth.
How do you do the math?
Thanks

The gts 250's banwidth is 70gb. How does that compare to say my 128 bit hd5750 at 1375 (5500) memory?

http://en.wikipedia.org/wiki/Comparison_of_Nvidia_graphics_processing_units#GeForce_200_Series

http://en.wikipedia.org/wiki/Compar...ocessing_units#Evergreen_.28HD_5xxx.29_series

Easy way to check out the memory bandwidth of various cards.
HD5750 is 73.6GB/s vs 70.4GB/s for the GT250 (and 111.9GB/s for the GTX260)

But again, memory bandwidth isn't everything.

 

[happy medium]

http://en.wikipedia.org/wiki/Comparison_of_Nvidia_graphics_processing_units#GeForce_200_Series

http://en.wikipedia.org/wiki/Compar...ocessing_units#Evergreen_.28HD_5xxx.29_series

Easy way to check out the memory bandwidth of various cards.
HD5750 is 73.6GB/s vs 70.4GB/s for the GT250 (and 111.9GB/s for the GTX260)

But again, memory bandwidth isn't everything.

Thanks but is there a calculation to determine the bandwidth?
I'd like to know how much bandwidth extra I got from my overclock.
Stock memory 1150 vs overclocked @ 1375.

Funny they have the 5830's specs in there!
Did you notice that?

 

[Hey Zeus]

Lon,

How does the 260 stack up against the 5 series? Against the 4890

 

[T2k]

You can OC the hell out of those DDR5 modules on the 5770, not to mention the 40nm core that OC like crazy - which means I'd expect a fully OC'd 5770 to be on par with a 4890 while eating the same and giving you a bunch of extra features like DX11, DP, Eyefiniti etc for ~$180... and there is the option to add another one, moving your setup between 5850 and 5870... 🙂

 

[T2k]

Yep, my guess was right on: http://www.xbitlabs.com/articles/video/display/radeon-hd5770-hd5750-crossfirex.html

 

[toyota]

Thanks but is there a calculation to determine the bandwidth?
I'd like to know how much bandwidth extra I got from my overclock.
Stock memory 1150 vs overclocked @ 1375.

Funny they have the 5830's specs in there!
Did you notice that?

1150mhz gddr5 is 1150x4 for 4600mhz effective
1375mhz gddr5 is 1375x4 for 5500mhz effective

now just multiply the effective memory speeds times the bus width and divide by 8.

4600x128=588800
588,800/8=73,600 or 73.6 gb/s bandwidth

5500x128=704800
704800/8= 88,000 or 88.8 gb/s bandwidth

that may not be the official way to check bandwidth but it gives the correct results.

 

[formulav8]

Like some others has mentioned, the 128bit bus may not look great, but with the DDR5 ram its much less of a issue like it used to be. Some 128Bit DDR5 buses are pushing 256Bit DDR3 numbers.

The biggest buster for low memory bandwidth is running lots of AA in your games. And also depending on the resolutions you are wanting to run.

Just my penny. 🙂


Jason

 

[Hey Zeus]

Like some others has mentioned, the 128bit bus may not look great, but with the DDR5 ram its much less of a issue like it used to be. Some 128Bit DDR5 buses are pushing 256Bit DDR3 numbers.

The biggest buster for low memory bandwidth is running lots of AA in your games. And also depending on the resolutions you are wanting to run.

Just my penny. 🙂


Jason

I run 1920X1200 with some AA

 

[T2k]

I run 1920X1200 with some AA

Unless you have a 26" or bigger monitor there's not much difference running without AA in 1920x1200 and AA on 5xxx is much better than 48xx anyway.

 

[T2k]

like some others has mentioned, the 128bit bus may not look great, but with the ddr5 ram its much less of a issue like it used to be. Some 128bit ddr5 buses are pushing 256bit ddr3 numbers.

The biggest buster for low memory bandwidth is running lots of aa in your games. And also depending on the resolutions you are wanting to run.

Just my penny. 🙂


jason

qft

 

[MarcVenice]

Memory bandwith becomes an issue at higher resolutions/more AA. Been testing a few lappy's with a GTS 250M and a GTX 260M. The latter only really pulls away at higher resolutions (1680x1050) or when more AA is used (1366x768 and 4xAA).

But I reckon that doesn't really helps you much. Maybe just wait for the HD 5830? I mean, a 5770 isn't al that fast for 1920. For me it would simply be to slow, HD 5850 would probably be the best choice for 1920 though.