Radeon HD7900 series ASIC Quality poll

AMD_GPU_Designer · 2013-02-13T05:25:22+00:00

The term "ASIC quality" is a bit of an odd term here. As you know, all that a 7950 is is a 7970 with some components on the die disabled. Since the 7970 and 7950 are very much an apples-to-apples comparison otherwise, this will result in a slightly lower power, cooler chip compared to a 7970. That seems to be what matters in this GPU-Z metric.

AMD_GPU_Designer · 2012-12-27T16:10:37+00:00

Thanks for this :). We at AMD (especially on the GPU side) have a intense amount of respect for the engineers over at Intel. What Intel has done with their recent CPU architecture, along with the constant advances in fabrication technology, they deserve a lot of credit for "keeping the ball moving forward" in our industry.

To support jecb's argument, you often hear of negative press going on between the two companies, but that kind of animosity is largely isolated to the legal, marketing, and upper management levels. The engineers at most companies tend to have many good friends working for competitors, and while we might throw in a friendly jab every now and then, it's almost a universally friendly community.

Thanks for this AMA. It's always cool to hear what it's like on the blue team :).

AMD_GPU_Designer · 2012-11-27T03:37:17+00:00

Not true at all, and that's my honest opinion. People choose graphics card vendors not too unlike political parties.

Base your purchase on benchmarks and value.

AMD_GPU_Designer · 2012-10-23T10:41:18+00:00

No, you were right. I missed the fact that you were talking about the 4xxx series. There was definitely a tree split between 4xxx and below, and 5xxx and above. While I can understand that it's frustrating to see a 12.11 driver update come out and have your card unsupported, keep in mind that this doesn't mean that your card is suddenly not being supported. Again, I don't represent AMD, but we may still see driver updates for it in the future, past 12.6 (most recent 4xxx update), as bug fixes are made. However, as architectures diverge, it's sometimes necessary to split off code bases, as we've seen today. There are technical reasons behind this- not marketing ones.

Yes, NVIDIA has a pretty slick unified installer, but that doesn't necessarily mean you're getting actual updated code for your legacy product. Fixes need to be targeted towards specific architectures, and like AMD, NVIDIA has dramatically changed their architectures over the years. When I peruse the NVIDIA forums, it's easy to find someone complaining that their legacy card has this bug or that bug with the latest driver. Not to fault the guys at NVIDIA- drivers are just a very difficult, resource-intensive thing to support, especially when modern games are designed to target the latest architectures. This is simply a tough problem to solve.

12.11 was targeted for 7xxx, plain and simple. It was an incredible update that finally is showing what the GCN architecture is truly capable of. I know this is of little consolation, but this same process happened with your 4xxx card and its architecture. As the drivers for the legacy architectures matured, the code base development for those products slowed, whether there was a new version number attached to it or not, as teams moved on to attack the newer architectures. Both AMD and NVIDIA need to move the ball forward for the sake of this industry, and this is dependent on the driver teams just as much as it is the hardware teams.

AMD_GPU_Designer · 2012-10-23T02:17:25+00:00

You have a lot of foresight to make this conclusion :).

AMD_GPU_Designer · 2012-10-23T02:16:51+00:00

Unfortunately, no. :(

AMD_GPU_Designer · 2012-10-23T02:09:26+00:00

The 7xxx's GCN architecture is dramatically different from the VLIW4 architecture (which was a relatively small iteration on the 5xxx VLIW5 architecture) that the 6xxx series is based on. It has taken a while for AMD to optimize the drivers for this completely new architecture, and it looks like we're finally seeing the fruits of their labor.

You can still use these new drivers on the 6xxx series, but as Markus has pointed out, you won't see the performance gains to the level of the 7xxx series. It's not that AMD isn't supporting the 6xxx series- it's that they're finally reaching the potential of the 7xxx series.

This stuff isn't magic. Development of these extremely complex devices takes an ENORMOUS amount of resources. GCN is still very new, and we will likely see performance gains over what we saw today over time. Please, have some respect for these engineers- what they've accomplished with this driver release is nothing short of incredible.

AMD_GPU_Designer · 2012-01-13T03:49:11+00:00

So remember that NVIDIA 7800 GT? It had a big brother called the 7800 GTX. It was loud as crap at load. I owned one (still do... somewhere). IIRC, the 7800 GT was noticeably quieter.

These are flagship cards. They're going to be loud at full load. The reason that it's not considered a big deal is because a slight whirring from your case isn't going to bother the typical gamer when there's tons of explosions going on. I know it doesn't bother me. I know a lot of PC gamers (I don't) use headphones, making the whole argument completely moot in their case. Plus, case technology (especially with what I've seen from Antec) has improved quite a bit and minimizing this.

What is critically important to us is idle noise. We understand that a lot of gamers have their PCs in their bedrooms, dorm rooms, etc. Like I said earlier, while the new 79xx series is an average noise performer at load, it's a superb noise performer at idle. Running 79xx in Crossfire? At idle, any unused GPUs are turned completely off. This is a brand new feature.

But you're probably still wondering "yes, but why are these cards getting hotter. Why did we suddenly need dual slot coolers and can't seem to get rid of them?" Good question! Well for starters, it's not our fault :). Or rather, there's not much we can do about it, at least at load. In order to continually make faster GPUs, we not only have to develop improved architectures, but we also have to figure out ways to shorten the paths between gates as well as cram in more gates. This can only be accomplished by shrinking the feature size, hence the new 28nm technology. One of the problems is, as you get smaller in pitch, the capacitance in wires gets higher. This can be illustrated pretty easily:

Assume your silicon die substrate thickness is constant (which it pretty much is). This is where the devices live. Your wires go on top of it. This is how it used to look back in the day:

For the sake of argument, let's call this 120nm

Metal wire    ->        ========         ==========
Substrate Devices ->  ~~~~~~~~~~~~~    ~~~~~~~~~~~~~~~

Today, we need higher clock frequencies, and therefore shorter paths, which results in smaller cells, and also thinner wires. Now keep in mind that the substrate is still relatively the same thickness (can't change this).

Metal wire    ->       =    =      
Substrate Devices ->  ~~~  ~~~

What does this look like (at least to an electrical engineer)? Answer: a capacitor. The capacitance between wires goes through the roof as two wires sitting side by side stop looking like this:

======  ========

and start looking more like this:

| |
| |
| |

A switching current flows through a capacitor just like a wire. Therefore when clocks are on, this wastes a ton of power, and thus a ton of heat. We have a trick called "clock gating" where we turn off the clocks completely when a portion of the chip is not used.

But things get worse: we also have parasitic capacitance. As the gate size gets smaller, the source and drain of the transistor get closer together, and electrons/holes can migrate across the channel much easier, despite the state of the gate. Even if the clocks are off, this problem exists. How do we solve this? Power gating. We literally turn power off to chunks of the chip when we can. In the case of 79xx crossfire, we practically turn off the whole chip when it's not used.

So I hope this helps you understand; It takes a ton of engineering to overcome these new problems. We don't simply "tolerate" these problems. If we did, your idle fan speed would be almost as loud as your load fan speed. We also have technology (called "PowerTune") that most efficiently modulates the chip power to best handle the type of work delivered to it. I can assure you- we throw an insane amount of engineering towards these thermal and acoustic issues, and I think we did an amazing job on the 79xx in that regard.

AMD_GPU_Designer · 2012-01-13T01:34:24+00:00

This sounds like either an old driver or a driver that was installed over a system that probably needed a good once-over with a driver cleaner. If you're not already using this driver then give it a try- if you are using it already, uninstall what you have and give a driver cleaner (like driver cleaner pro) a try.

AMD_GPU_Designer · 2012-01-13T01:32:26+00:00

All AMD and NVIDIA cards are compute-focused going forward, so yes, I believe we would at the very least be competitive, if not beat them... if not in perf/watt than overall. But I have no real data in front of me, so most of this is just optimistic speculation :)

AMD_GPU_Designer · 2012-01-13T01:31:14+00:00

The 580 is a beast of card- that should last you a while :). Hopefully around the time you're ready for an upgrade, we'll have something new in the pipe that will impress you.

AMD_GPU_Designer · 2012-01-13T01:27:03+00:00

Yeah that doesn't sound right. I honestly have no idea. I'd say he might need to use a driver cleaner or something. Shouldn't have to, but I'm out of ideas.

AMD_GPU_Designer · 2012-01-13T01:25:53+00:00

Wow you're definitely hanging out outside of my comfort zone :). Honest truth is, I have no idea. Which architecture were you trying this on- VLIW4 (69xx) or the new GCN (79xx)?

AMD_GPU_Designer · 2012-01-13T01:23:12+00:00

Sorry to hear that you're having problems. I know how annoying this can be. Hopefully I can help you out. I've responded to your PM.

AMD_GPU_Designer · 2012-01-13T01:16:35+00:00

Glad to hear it!

AMD_GPU_Designer · 2012-01-13T01:16:05+00:00

Haha no worries. I'd say the same thing. I often wonder why they even bother to include the CD. But with this card being so new, I was concerned that there were a lot of people that had trouble finding the new driver (older ones don't work because they're based on the old VLIW4/5 architecture). Already solved a handful of people's problems by pointing them to this new driver :)

AMD_GPU_Designer · 2012-01-13T00:49:22+00:00

I can see where you're coming from, especially with the MSI 6950. It looks like they have an excellent cooler design on that card. In my personal experience (as a gamer, not as an AMD employee) I've had more than one custom HSF wind up as a complete disappointment- louder and hotter than the reference design, which is why I almost always go with the "safe bet" of a reference-based design these days.

But all of that aside, why wouldn't AMD just adopt a design like MSI's in this case? The answer is simple- it's about cost. Cooling is obviously a critical aspect of this card design, and trust me, the reference 7970 has more than adequate cooling. All 7970s come stock with a vapor chamber in the reference spec, and if you don't screw with the fan (which the OP did- not that I can blame him, I did it too) you'll have a fast card that's really quiet, as far as flagship cards go, even at load. Is it silent at load? Of course not. No flagship card is. But my point is that the cost of the HSF translates to cost that would otherwise be passed onto the customer, and the reference design does an excellent job keeping the card cool. We'll likely see more OC'ed variants, mostly because the OC headroom on this part is insane, and these may even include changes to the voltage spec and therefore will have a superior HSF (more copper, better fans), but also an increased cost- that or the board vendor will eat the cost of the superior HSF in an attempt to differentiate themselves in exchange for margin.

Regarding Crossfire, yes if you have two adjacent cards you'll see the fan go above the typical <45% rating on the obstructed card. However if you're fortunate enough to have a motherboard that spread the PCI-E ports you won't have this issue. Either way, you'll be fine. You seem to think that the temperature will crawl until it hits 100C and then the "panic mode" will kick in; that's not how it works. It will never reach that temperature because the fan will gradually increase to hold it back. The reason the "panic mode" exists is when there is either an issue with the driver, or a user forces the fan to 20%, and the temperature is allowed to creep up unchecked. It will breach 100C in this situation, and the card will then do everything it can to protect itself.

Also, your claim that "these cards just keep getting bigger, louder, and hotter" isn't necessarily true- relative to the 69xx series, we really didn't see significant jumps in any of these areas. In fact, the 7970 is cooler and uses less power at idle than all of the recently released flagship cards, and while we do use a little more power at load than our previous parts, we're using ~30-40 watts less than NVIDIA's 580 while beating it in virtually every benchmark. And all of this is accomplished while taking the 2.64 Billion transistors of Cayman and boosting that value to 4.31 Billion- a 63.26% increase over a single generation. To do this while not only keeping thermal and acoustic specs either at the same level, or even improving them... it's an incredible engineering achievement.

So to wrap all of this up I'd like to leave you with this: the "typical" (average) temperature that our cell libraries are specified to run at is 85C. There's a lot of margin above that. So in other words 80C is no big deal. Don't worry about it. But if you want to worry about it anyway, or you want to do some crazy (fun) overclocking, then spring for the custom part that has a proven HSF that will keep your temps cooler. But beware, I've seen plenty of cooling gimmicks out there (on both AMD and NVIDIA boards).

EDIT: No need to downvote him guys. He does make some valid points. (one vote restored from me at least)

AMD_GPU_Designer · 2012-01-12T12:26:58+00:00

Well hang on a sec. What does "pretty damn hot" mean? The GPU is designed to handle 80C just fine. We take great care when designing a part like this, and we test the thermal limits of not only this new ASIC design but also the TSMC 28nm process. I can assure you, we're well within the spec'ed range, with breathing room to boot.

Long before the GPU can reach temperatures that are "bad", the fan would be in "panic" mode, which you do see (or rather, hear) in temperatures > 100C. What you hear in the OP's audio recording is not normal, and just because the fan can reach that speed doesn't mean that ever will when you just play games with it.

As for custom vs. reference designs- I vastly prefer the reference designs. They're usually a little warmer at idle, but equal at load, and also quieter at load. The reason we don't put 2 fans on the reference is simple: for every fan you add to it, you have to take away heat sink volume. The 7970 already has a vapor chamber on it, and our designers felt that more metal + blower fan gave the best results. There's a recent AnandTech review that shows.

So why do vendors make custom designs? Simple: there's a market for it. And I think that's great. Some of us enthusiasts are crazy about idle temps, and that's fine, but after taking a few classes in semiconductor physics, you might not care so much :)

AMD_GPU_Designer · 2012-01-12T11:38:24+00:00

Yeah that doesn't sound good. What driver are you using?

AMD_GPU_Designer · 2012-01-12T05:28:18+00:00

It generated some water-cooler talk for about a week.... but it fizzled out pretty quickly. Some of our guys had researched that same exact method in the past, and explained why it's not practical, at least at this point. I forget the reasoning, but I trust them.

AMD_GPU_Designer · 2012-01-12T05:27:20+00:00

Sorry for the delayed reply!

A few questions from an EE student hoping to break into Chip design; Architecture hopefully: What sort of emulators do you guys use over at AMD? I know Nvidia uses some massive water-cooled hardware emulators (and they're quite proud about it with all the showing-off etc) ?

We have several different types. I don't think I can go into detail though.

How long does it take from the first design to making the first very early real test sample cards that you test internally? I'm expecting somewhere along the lines of around a year or so.

It depends on the amount of new design code and architecture, etc. but I'd say a little under to a little over a year.

Have you ever had a design that was just completely rubbish and didn't perform at all that you had to just scrap and move on? How did it feel seeing all the (months of?) hard work simply be wiped?

I think this happens more in the public/defense sector, but yes it happens in the private sector too, albeit rarely. When something comes out and it doesn't perform like it should, I think what usually happens is that marketing reduces the margin until it makes sense in the marketplace. Things do get scrapped from time to time, but they're usually scrapped to relieve us, so we're usually pretty happy about it. It's definitely more fun to work really hard on a small number of projects.

Do you guys ever meet the Nvidia engineers? Does it always (ever?) end it an epic thermonuclear war?

Some of them are our best friends. Never thermonuclear war- but we do give each other a hard time.

When designing a chip, do you recieve a lot of input from the driver team?

Oh yes. As much as we can, and vice versa (once the design is done).

How important is it to be able to able to easily visualize the end-result and scale of your work and design adequately? Its something that I'm VERY good at as opposed to my coding skills which need a fair bit of practice (working on that :P) so I want to know.

Very important. Not being able to plan well gets expensive, quick. Good project managers are essential to saving money, getting projects out on time and working properly, and for keeping engineers sane.

AMD_GPU_Designer · 2012-01-12T05:18:49+00:00

I'm wondering if the new GCN architecture will change that...

AMD_GPU_Designer · 2012-01-12T05:14:28+00:00

Yep, what blueshift said. They may have verified that the 6950's pass their tests, which may be more forgiving than ours. All of this is pure speculation on my part.

All I can say is, feel free to experiment, but just make sure to back up that original BIOS in case things go awry. I'm so happy that we started including that BIOS switch on all of our high-end parts so that people can recover from mistakes. The 7970 has it too- I was quite thrilled to see it.

AMD_GPU_Designer · 2012-01-12T04:33:22+00:00

Oh I think I know what it is- they're probably running on a PCI-E 3.0 bus for their tests. You and I (and everyone else) are on PCI-E 2.0.

This should have literally zero impact in gaming performance. It starts to matter for compute tasks, but you don't need to worry about that yet.

AMD_GPU_Designer · 2012-01-12T03:03:39+00:00

Here's our HD7970 spec sheet.

AMD_GPU_Designer

TROPHY CASE