Gtx 970 issues

Gtx 970 issues DEFAULT

Nvidia got a lot of gamers excited when it unveiled the GeForce GTX 970 last September, and for good reason: It’s a powerhouse of a graphics card for just $330. We were duly impressed with the 970 after pitting it against some AMD GPUs and Nvidia’s own higher-priced GTX 980 in a graphics card slugfest last fall.

But gamers have since complained that the GTX 970 seems to falter under pressure when a game tries to use more than 3.5GB of the card’s 4GB of VRAM.

Nvidia recently addressed these complaints and admitted the performance issues weren’t the result of overzealous imaginations, a firmware flaw, or a few bad units rolling off the production line. The problem was the way Nvidia designed the memory for the GTX 970. It also turns out that some of Nvidia’s originally reported specs for the GTX 970 were wrong.

Why this matters: The revelations about the GTX 970 leave Nvidia in an embarrassing situation. Not only does it have to account for why some edge case-users may be experiencing performance problems, but the company had to come clean about giving reviewers incorrect specs, and not correcting them for months. It’s a problem for Nvidia, but it’s more important that anyone looking at graphics cards understands the limitations of the GTX 970—limitations that should’ve been made public from the start.

Big, little

Although the 970 has 4GB of VRAM, not all of that memory is created equal. The 970 has two different segments of memory it can access, as Nvidia recently explained to PC Perspective: a primary segment with 3.5GB and a secondary, slower one with another 512MB. 

Under normal conditions (and the vast majority of gaming scenarios), the card relies on the 3.5GB segment alone, turning to the supplementary segment only when necessary. But when a game needs more than 3.5GB of memory, tapping into the secondary segment drags down performance. Some are reporting stutters and frame rate drops as the card uses between 3.5GB and 4GB of memory.

Nvidia GeForce GTX 980

Another issue, as reported by AnandTech, is that the GTX 970 came with fewer render output units (ROPs) than originally claimed. ROPs are directly tied to a card’s performance and the GTX 970 was reported as having 64, when it actually has 56. The GTX 970 also has a smaller L2 cache than originally stated, at 1.75MB instead of 2MB. Nvidia told AnandTech the discrepancy was the result of an error by the technical marketing team rather than an attempt at duplicity. 

What it means to you

Despite these shortcomings, however, the GTX 970 still delivers an amazing amount of bang for your buck. The difference now, as AnandTech points out, is that we have a better understanding of the card’s strengths and weaknesses. While the issues introduced by the memory design may only be bumped into in edge cases, they may sway gamers who want to play at very high resolutions and/or with anti-aliasing settings cranked to the max to consider AMD’s Radeon cards, as those situations require more memory than typical gaming scenarios.

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The flagship Radeon R9 290X delivers performance similar to the GTX 970 in most cases, includes 4GB to 8GB of memory with a wider 512-bit memory bus (as opposed to the GTX 970’s 256-bit bus), and can often be found for less than the $330 and up Nvidia card—and sometimes far less if you can find juicy rebates. That makes the Radeon better suited for situations that require more memory—again, very high resolutions and/or cranked anti-aliasing settings—but AMD’s cards are far less energy efficient than Nvidia’s. Decisions, decisions. 

And surprise! There’s already a Change.org petition by upset GTX 970 buyers demanding a refund from Nvidia.

For more in-depth details about the GeForce GTX 970’s memory details, be sure to check out AnandTech’s in-depth examination of the issue, which spans multiple pages and is chock full of nitty-gritty details.

Sours: https://www.pcworld.com/article/431499/nvidia-explains-geforce-gtx-970s-memory-performance-issues-admits-error-in-specs.html

Report: Nvidia has settled class-action lawsuit over the GTX 970’s 3.5GB memory issue

GTX970

When Nvidia launched the GTX 970 and 980 back in the fall of 2014, Maxwell quickly rose to prominence thanks to strong performance and excellent power efficiency. Early reviews showed good results on both cards, but deeper dives into the GTX 970 post-launch turned up troubling behavior: The card strongly preferred to limit its available memory to 3.5GB, not the 4GB it actually carried. A class-action lawsuit was launched a month after the problem came to light, and Nvidia has apparently resolved that case as of today.

Nvidia will pay each GTX 970 owner that applies an average of $30 (there’s no information yet on how one applies for the refund) in addition to paying $1.3 million in attorney fees, according to Overclockers3D. While $30 isn’t huge, it presumably accounts for the estimated value of the effectively-missing 512MB of RAM.

For those of you who don’t recall the details of the issue, the problem was this: The GTX 970’s internal memory configuration disabled one of its crossbar switches, as shown in the diagram below:

diagram2

GTX 970’s memory subsystem

The “SM” blocks in this diagram are the actual processor cores, while the L2 blocks refer to the L2 cache. “MC” blocks are the memory controllers. The chip is designed so that any SM block could talk to any of the memory controllers, but three of the SM blocks and one of the L2 cache blocks is grayed out in this diagram. The SM blocks are disabled to hit the GTX 970’s core count target, but the last block of L2 cache does double duty, serving two SM blocks rather than just one. Disabling L2 cache blocks in this fashion also reduced the GTX 970’s ROP count to 56 down from 64 (as Tech Report noted at the time, actual throughput was actually a maximum of 52 pixels per clock due to associated limitations in the crossbar).

Nvidia PR claimed that the GTX 970’s original specs were miscommunicated to reviewers, and I believe them. There’s a difference between cherry picking results and arguments to favor any company’s given position on a topic, and flatly misrepresenting the capabilities of one’s hardware in an attempt to drive sales under false pretenses. The former is expected, the latter is criminal. The net effect of this problem was to leave the GTX 970 with a 512MB memory buffer that was technically available to games if absolutely required, but could only be accessed at a fraction of the speed of main memory, as shown in the results below:

Nvidia memory test

Practically speaking, the impact on the vast majority of users was minimal. Benchmarks and tests showed that there were games that could trip the GTX 970, but this often only occurred at the limits of playable frame rates in any case. Overall, the GTX 970 sold well and became one of the most popular GPUs of the previous generation. Given that recent price cuts have left it priced as low as $260 (as of this writing), it’s not a bad deal even now — though generally speaking I’d still recommend either the RX 480 or the GTX 1060, depending on your preferences. While the GTX 970 should be fine for 1080p and below in the indefinite future, there’s always the chance that this RAM problem will bite as VRAM requirements continue to scale up.

Sours: https://www.extremetech.com/gaming/232610-report-nvidia-has-settled-class-action-lawsuit-over-the-gtx-970s-3-5gb-memory-issue
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Why Nvidia's GTX 970 slows down when using more than 3.5GB VRAM

Last week, commenters on Nvidia’s forums, reddit, Guru3D and elsewhere started digging into what looked to be a concerning problem: the GeForce GTX 970 only seems to use 3.5GB of its 4GB of VRAM. Few games can really utilize 4GB of VRAM, but some commenters noted a serious drop in performance or stuttering when pushing the GTX 970 over the 3.5GB threshold. The same problem did not appear to affect the GTX 980.

Nvidia responded on Friday with this statement (and chart):

“The GeForce GTX 970 is equipped with 4GB of dedicated graphics memory. However the 970 has a different configuration of SMs than the 980, and fewer crossbar resources to the memory system. To optimally manage memory traffic in this configuration, we segment graphics memory into a 3.5GB section and a 0.5GB section. The GPU has higher priority access to the 3.5GB section. When a game needs less than 3.5GB of video memory per draw command then it will only access the first partition, and 3rd party applications that measure memory usage will report 3.5GB of memory in use on GTX 970, but may report more for GTX 980 if there is more memory used by other commands. When a game requires more than 3.5GB of memory then we use both segments.

The best way to test that is to look at game performance. Compare a GTX 980 to a 970 on a game that uses less than 3.5GB. Then turn up the settings so the game needs more than 3.5GB and compare 980 and 970 performance again.

Here’s an example of some performance data:

GTX980GTX970
Shadows of Mordor
72fps60fps
>3.5GB setting = 3456x194455fps (-24%)45fps (-25%)
Battlefield 4
36fps30fps
>3.5GB setting = 3840x2160 135% res19fps (-47%)15fps (-50%)
Call of Duty: Advanced Warfare
82fps71fps
>3.5GB setting = 3840x2160 FSMAA T2x, Supersampling on48fps (-41%)40fps (-44%)

On GTX 980, Shadows of Mordor drops about 24% on GTX 980 and 25% on GTX 970, a 1% difference. On Battlefield 4, the drop is 47% on GTX 980 and 50% on GTX 970, a 3% difference. On CoD: AW, the drop is 41% on GTX 980 and 44% on GTX 970, a 3% difference. As you can see, there is very little change in the performance of the GTX 970 relative to GTX 980 on these games when it is using the 0.5GB segment.”

It’s hard to analyze the effect of pushing either card past 3.5GB of VRAM with the numbers provided above; the framerate will naturally be lowered by running a game at higher resolution or AA settings. Nvidia’s point is that the GTX 970 behaves just like the 980, with performance only decreasing about 1-3%, comparatively.

Those are also average framerates, which don’t address the problem some commenters have pointed out: dramatic framerate stutter at the moment the GTX 970 starts utilizing its final 500MB of VRAM. This user-created Nai’s Benchmark claims to show that the memory bandwidth of the GTX 970 drops dramatically when accessing that last 500MB, while the same problem does not affect the GTX 980. These numbers look bad, though we can’t vouch for the veracity of data provided by the benchmark.

On Sunday, Nvidia Senior VP of GPU Engineering Jonah Alben spoke to PC Perspective about the issue, and we finally have clarification on where that discrepancy comes from. PCPer writes:

“The most important part here is the memory system... connected to the SMMs through a crossbar interface. That interface has 8 total ports to connect to collections of L2 cache and memory controllers, all of which are utilized in a GTX 980. With a GTX 970 though, only 7 of those ports are enabled, taking one of the combination L2 cache/ROP units along with it. However, the 32-bit memory controller segment remains.

"You should take two things away from that simple description. First, despite initial reviews and information from NVIDIA, the GTX 970 actually has fewer ROPs and less L2 cache than the GTX 980. NVIDIA says this was an error in the reviewer’s guide and a misunderstanding between the engineering team and the technical PR team on how the architecture itself functioned. That means the GTX 970 has 56 ROPs and 1792 KB of L2 cache compared to 64 ROPs and 2048 KB of L2 cache for the GTX 980. Before people complain about the ROP count difference as a performance bottleneck, keep in mind that the 13 SMMs in the GTX 970 can only output 52 pixels/clock and the seven segments of 8 ROPs each (56 total) can handle 56 pixels/clock. The SMMs are the bottleneck, not the ROPs.”

If you don’t speak graphics card, PCPer helps break down the architecture of the GTX 970. Because the GTX 970 only has seven ports connecting memory controllers and cache, one of those ports would always be burdened with twice as many requests.

PCPer explains “if the 7th port is fully busy, and is getting twice as many requests as the other port, then the other six must be only half busy, to match with the 2:1 ratio. So the overall bandwidth would be roughly half of peak. This would cause dramatic underutilization and would prevent optimal performance and efficiency for the GPU.”

Nvidia avoided that problem by dividing the memory into a 3.5GB pool and a 0.5GB pool. Few games (currently) require more than 3.5GB of VRAM, so the primary pool can be accessed at maximum bandwidth.

PCPer writes: “Let's be blunt here: access to the 0.5GB of memory, on its own and in a vacuum, would occur at 1/7th of the speed of the 3.5GB pool of memory. If you look at the Nai benchmarks (pictured above) floating around, this is what you are seeing.”

Accessing that last 500MB of VRAM is absolutely slower than accessing the first 3.5GB. What we don’t know, exactly, is how much that actually matters for gaming. PCPer points out that the last chunk of VRAM is still four times faster than system RAM (your DDR3) accessed via PCIe. The GTX 970 does have 4GB of VRAM, and it can use all of it, but accessing those last 500MB will decrease performance.

We’re doing our own testing to see if we can determine how much impact using the last chunk of VRAM has on gaming. Having used the GTX 970 extensively, we can still say that it’s a fantastic card for the price and an overclocking beast. But that doesn't excuse Nvidia’s omission, intentional or accidental, as PCPer highlights: “at the very least, the company did not fully disclose the missing L2 and ROP partition on the GTX 970, even if it was due to miscommunication internally.”

We’ll have more on this issue as we continue testing. Thanks to PC Perspective for their excellent reporting.

When he's not 50 hours into a JRPG or an opaque ASCII roguelike, Wes is probably playing the hottest games of three years ago. He oversees features, seeking out personal stories from PC gaming's niche communities. 50% pizza by volume.
Sours: https://www.pcgamer.com/why-nvidias-gtx-970-slows-down-using-more-than-35gb-vram/

Nvidia Responds To GTX 970 3.5GB Memory Issue

There have been numerous reports of the GTX 970 suffering from a memory allocation issue limiting it to 3.5GB instead of the full 4GB. We've done our own testing and analysis of this issue here at Wccftech.com in a previous piece. And in this article we aim to explain the issue in totality, why it occurs, what it means and how it affects users.

NVIDIA GM204 GPU Powering the GTX 980 and GTX 970This whole debacle started when GTX 970 users began reporting an issue with memory allocation on their cards. The issue specifically was around the GTX 970 not being able to address all of the 4GB of on-board GDDR5 memory that Nvidia has equipped its cards with.  GTX 970 users continuously reported maximum memory usage hitting a wall at 3.5GB. Shortly afterwards we went ahead and tested out the GTX 970 to try and see where this issue is stemming from. What we had discovered was quite interesting and goes hand in hand with Nvidia's latest response to this issue. But before we discuss our findings let's see what Nvidia has to say first.

Nvidia Responds to GTX 970 Memory Allocation Issue

In a recent statement to PCPer.com Nvidia admitted the existence of a memory allocation behavior that led so many GTX 970 users to worry. The company also offered a brief explanation of the phenomenon and why it occurs.

"The GeForce GTX 970 is equipped with 4GB of dedicated graphics memory.  However the 970 has a different configuration of SMs than the 980, and fewer crossbar resources to the memory system. To optimally manage memory traffic in this configuration, we segment graphics memory into a 3.5GB section and a 0.5GB section.  The GPU has higher priority access to the 3.5GB section.  When a game needs less than 3.5GB of video memory per draw command then it will only access the first partition, and 3rd party applications that measure memory usage will report 3.5GB of memory in use on GTX 970, but may report more for GTX 980 if there is more memory used by other commands.  When a game requires more than 3.5GB of memory then we use both segments.

We understand there have been some questions about how the GTX 970 will perform when it accesses the 0.5GB memory segment.  The best way to test that is to look at game performance.  Compare a GTX 980 to a 970 on a game that uses less than 3.5GB.  Then turn up the settings so the game needs more than 3.5GB and compare 980 and 970 performance again.

Here’s an example of some performance data:

GTX 980GTX 970
Shadow of Mordor
<3.5GB setting = 2688x1512 Very High72 FPS60 FPS
>3.5GB setting = 3456x194455 FPS (-24%)45 FPS (-25%)
Battlefield 4
<3.5GB setting = 3840x2160 2xMSAA36 FPS30 FPS
>3.5GB setting = 3840x2160 135% res19 FPS (-47%)15 FPS (-50%)
Call of Duty: Advanced Warfare
<3.5GB setting = 3840x2160 FSMAA T2x, Supersampling off82 FPS71 FPS
>3.5GB setting = 3840x2160 FSMAA T2x, Supersampling on48 FPS (-41%)40 FPS (-44%)

On GTX 980, Shadows of Mordor drops about 24% on GTX 980 and 25% on GTX 970, a 1% difference.  On Battlefield 4, the drop is 47% on GTX 980 and 50% on GTX 970, a 3% difference.  On CoD: AW, the drop is 41% on GTX 980 and 44% on GTX 970, a 3% difference.  As you can see, there is very little change in the performance of the GTX 970 relative to GTX 980 on these games when it is using the 0.5GB segment."

Nvidia's statement explains our own findings earlier. In our analysis we discovered that the GTX 970 can actually address and use all available 4GB of VRAM and not just 3.5GB. However the performance penalty for using that last 0.5GB of VRAM is still interesting. As Nvidia explains it and as we had suspected earlier, the issue is essentially due to the fact that the GTX 970 is based on a cut-down GM204-200 GPU die instead of the full GM204 chip like its bigger brother the GTX 980.

The GM204-200 GPU has three SMM units disabled, for a total of 13/16 SMMs. This in turn disables some components of the memory sub-system. This leaves the chip with less resources to manage the same amount of memory as the GTX 980. Which is why Nvidia resorted to the dual segment (3.5GB-0.5GB) memory arrangement. This in turn insures that the larger 3.5GB segment doesn't suffer any performance penalty.

Nvidia doesn't provide data to compare how a 970 would perform had it not exhibited this memory behavior. So I went ahead and calculated how the performance of the GTX 970 would've been affected had this memory allocation phenomenon was absent. I've done this by applying the performance scaling ratio of the GTX 980 ,which doesn't exhibit this behavior, to the GTX 970.

WccftechGTX 970 Performance in %GTX 970 Performance Without Memory Allocation Issue in %
Shadow of Mordor100% 102%
Battlefield 4 100% 105%
Call of Duty Advanced Warfare 100% 104%

Simply put the GTX 970 is only able to fully utilize 3.5GB out of the 4GB of available VRAM optimally. While the card can still access all 4GB of VRAM, the last 0.5GB of memory is not accessed or managed as efficiently as the rest of the available memory. Which leads to the reported performance degradation when an application needs to access more than 3.5GB. In the examples Nvidia provided to the press the performance penalty is in the mid single digit percentages. However we don't fully know yet if in other usage scenarios the memory issue will prove to be more detrimental. As there's evidence that it has a more perceptual impact on frame time consistency rather than FPS which can be perceived as the stuttering or choppiness reported by Nvidia users on the GeForce forums.

Most users should not face this issue except on higher resolutions such as 4K or in the case of multi-monitor gaming. In which case we would actually recommend buying a graphics card with more memory anyway. AMD already has 8GB R9 290X cards in the market which were introduced three months ago. Earlier rumors indicated that Nvidia was also launching 8GB variants of the GM204 based 900 series cards in November of last year but that unfortunately did not happen. Samsung SDRAM schedules indicate that Nvidia could launch 8GB variants of their 900 series cards this quarter.

Although with rumors looming of a GM200 launch taking place in two months time and AMD's HBM equipped Fiji XT coming soon after. I'd suspect that users would want to see how well products based on these new GPUs perform in the market and then make a decision.

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Sours: https://wccftech.com/nvidia-geforce-gtx-970-memory-issue-fully-explained/

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Nvidia explains the GeForce GTX 970's memory 'problems'

The GeForce GTX 970 supposed memory issue

You may have read about the recent Internet furore surrounding the GeForce GTX 970, a GPU that has sold by the proverbial buckletloads since launch in September 2014.

This furore picks up on the fact that the GeForce GTX 970's memory-bandwidth performance dives when more than 3.5GB out of the possible 4GB is used, and, crucially, this is a situation that doesn't arise with the seemingly architecturally-similar GeForce GTX 980.

Digging deeper and putting some numbers on these bones, the folks over at Lazygamer.net have shown that after approximately 3.3GB of usage the memory bandwidth of the GTX 970 tails off magnificently, from 150GB/s down to as low as 20GB/s - see the below image for more details.

Image credit: Lazygamer

The 'bug' has limited implications for the vast majority of users, granted, but readers interested in 4K gaming or using the new Dynamic Super Resolution (DSR) down-sampling technique may encounter problems.

The first NVIDIA response

Nvidia has since stepped into this supposed memory-bandwidth issue by issuing the following reply:

"The GeForce GTX 970 is equipped with 4GB of dedicated graphics memory.  However the 970 has a different configuration of SMs than the 980, and fewer crossbar resources to the memory system. To optimally manage memory traffic in this configuration, we segment graphics memory into a 3.5GB section and a 0.5GB section.  The GPU has higher priority access to the 3.5GB section.  When a game needs less than 3.5GB of video memory per draw command then it will only access the first partition, and 3rd party applications that measure memory usage will report 3.5GB of memory in use on GTX 970, but may report more for GTX 980 if there is more memory used by other commands.  When a game requires more than 3.5GB of memory then we use both segments.
 
We understand there have been some questions about how the GTX 970 will perform when it accesses the 0.5GB memory segment.  The best way to test that is to look at game performance.  Compare a GTX 980 to a 970 on a game that uses less than 3.5GB.  Then turn up the settings so the game needs more than 3.5GB and compare 980 and 970 performance again.
 
Here’s an example of some performance data:

 GTX 980GTX 970
Shadow of Mordor  
>3.5GB setting = 3456x194455 FPS (-24%)45 FPS (-25%)
Battlefield 4  
>3.5GB setting = 3840x2160 135% res19 FPS (-47%)15 FPS (-50%)
Call of Duty: Advanced Warfare  
>3.5GB setting = 3840x2160 FSMAA T2x, Supersampling on48 FPS (-41%)40 FPS (-44%)

 

On GTX 980, Shadows of Mordor drops about 24% on GTX 980 and 25% on GTX 970, a 1% difference.  On Battlefield 4, the drop is 47% on GTX 980 and 50% on GTX 970, a 3% difference.  On CoD: AW, the drop is 41% on GTX 980 and 44% on GTX 970, a 3% difference.  As you can see, there is very little change in the performance of the GTX 970 relative to GTX 980 on these games when it is using the 0.5GB segment."

What's going on, then?

Nvidia's first response admits the GeForce GTX 970's memory subsystem is composed differently to the GTX 980's - with a primary, fast 3.5GB partition and a secondary 0.5GB partition accessed only when needed - but doesn't go on to provide any meaningful technical insight other than to say that in-game performance barely suffers. Such a statement left us unsatisfied.

Just a couple of hours ago HEXUS was invited to chat with Jonah Alben, senior vice president of GPU engineering at Nvidia, who provided a high-level overview of the new memory subsystem employed by the GeForce GTX 970.

Nvidia and AMD make engineering decisions on how best to harvest the full-fat architecture of a particular class of GPU. The GM204's premier interpretation is the GeForce GTX 980. The GTX 970, meanwhile, appears to keep most of the GTX 980's goodness intact, save for the disabling of three of the 16 SMM units, thus pushing the number of cores down from 2,048 to 1,664, texture units from 128 to 104, and so forth. We praised Nvidia for keeping the heavy-lifting back-end the same as GTX 980, meaning 64 ROPs and 2,048KB of L2 cache. This, Jonah revealed, is not the case.

GTX 970 is not what you first thought it was

It turns out that GeForce GTX 970 56 ROPs, not the 64 listed on reviewers guides back in September and such knowledge leads to interesting questions. Nvidia has clearly known about this inaccuracy for some time but has deigned not to contact the technical press with an update or explanation. Having fewer ROPs isn't a huge problem for the top-end of the GeForce GTX 970 - we'll explain why a little later on - but does have important ramifications for the memory subsystem, and answers the 3.5GB/0.5GB issue referred to above.

This Nvidia-provided slide gives brief insight into how the GTX 970 is constructed. The three disabled SMs are shown at the top and 256KB L2s and pairs of 32-bit memory controllers on the bottom. Notice the greyed-out right-hand L2 for this GPU? Tied into the ROPs as they are this is a direct consequence of reducing the overall ROP count. GTX 970 has 1,792KB of L2 cache, not 2,048KB, but, as Alben points out, still has a greater cache-to-SMM ratio than GTX 980.

Historically, including up to the Kepler generation, cutting off the L2/ROP portion would require the entire right-hand quad section to be deactivated too. Now, with Maxwell, Nvidia is able to use some smarts and still tap into the 64-bit memory controllers and associated DRAM even though the final L2 is missing/disabled. In other words, compared to previous generations, it can preserve more of the performance architecture even though a key part of a quad is purposely left out. This is good engineering.

But while it's still accurate to say the GeForce GTX 970 has a 256-bit bus through to a 4GB framebuffer - the memory controllers are all active, remember - cutting out some of the L2 but keeping all the MCs intact causes other problems; there is no usual eighth L2 to access, meaning that the seventh L2 will be hit twice. The way in which the L2 work makes this a very undesirable exercise, Alben explains, because this forces all other L2s to operate at half normal speed.

Smoke and mirrors

Finally coming back to point, Nvidia gets around this L2 problem by splitting the 4GB memory into a regular 3.5GB section, constituted by seven MCs and associated DRAM, and a 0.5GB section for the last memory controller. The company could have marketed the GeForce GTX 970 as a 3.5GB card, or even deactivated the entire right-hand quad and used a 192-bit memory interface allied to 3GB of memory but chose not to do so. The thinking behind such a move revolves around the last L2 cache/MC partition combo still being considerably faster than the card having to run out over the PCIe bus and to system memory as is the case when the onboard framebuffer of any card is saturated.

The real question is how does this play out with the huge memory bandwidth drop-off in the Lazygamer Nia test versus Nvidia's statement that games barely suffer from this smart engineering? The Lazygamer test at the >3.5GB metric simply probes bandwidth on a single DRAM, which is admittedly low, or 1/8th of the total speed, while in-game code, according to Nvidia, doesn't necessarily pinpoint memory in this way. There's certainly a memory-bandwidth drop-off when the 0.5GB section is called into action, Alben states, but it's not anywhere near as severe if infrequently accesssed code is shunted into the last two MCs and DRAM.

In a high-level nutshell Nvidia is using smart engineering to get the most out of the GTX 970's architecture. The lack of total ROPs is relatively unimportant because this GPU cannot make use of them - the 13 SM units, running at four pixels per clock (so 52 in total), are limiting the GPU more so than the 56 processed by the ROPs. The GeForce GTX 970's performance hasn't changed, obviously, but Nvidia wasn't clear on how the back-end works... and it has taken investigation by enthusiasts to uncover the real reason why this 256-bit architecture isn't as good as the GTX 980's.

Nvidia stung into action?

We've learned that the GeForce GTX 970 is more than an SMM-reduced version of the GTX 980, which is a fact that will come into play once that 0.5GB is routinely accessed. We've learned that Nvidia has chosen not to impart the GTX 970's differences until Internet rumours surfaced on a potential memory-bandwidth issue, and we have learned that Nvidia has known all along that the information passed along to reviewers - ROP counts, L2 cache, etc. - has been wrong... and has done nothing about it until forced to do so when speculation grew too rife.

There are hundreds of behind-the-scenes tweaks made to each iteration of a GPU architecture. Some of the more important ones, particularly with regards to high-level architecture, should be disclosed from the get-go. Nvidia chose not to with the highly-accomplished GeForce GTX 970, wrongly in our opinion, and while the under-the-hood tweaks don't materially change performance by any degree, Nvidia should have been very clear that the GeForce GTX 970 and GTX 980 use different back-end technologies, more so for buyers who can tax the main 3.5GB framebuffer when gaming at 4K.

What do you, the gamers, make of Nvidia's initial reluctance to share how the GeForce GTX 970 really works? Or do you even care, because performance hasn't changed one iota from yesterday to today?

Sours: https://hexus.net/tech/news/graphics/79925-nvidia-explains-geforce-gtx-970s-memory-problems/
Does the GTX 970 VRAM Issue Still Matter?

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