AMD Radeon HD 7790 Review Feat. Sapphire: The First Desktop Sea Islands
by Ryan Smith on March 22, 2013 12:01 AM EST- Posted in
- GPUs
- AMD
- Sapphire
- GCN
- Radeon HD 7000
The New PowerTune: Adding Further States
In 2010 AMD introduced their PowerTune technology alongside their Cayman GPU. PowerTune was a new, advanced method of managing GPU voltages and clockspeeds, with the goal of offering better control over power consumption at all times so that AMD could be more aggressive with their clockspeeds. PowerTune’s primary task was to reign in on programs like FurMark – power viruses as AMD calls them – so that these programs would not push a card past its thermal/electrical limits. Consequently, with PowerTune in place AMD would not need to set their maximum GPU clocks as conservatively merely to handle the power virus scenario.
This technology was brought forward for the entire Southern Islands family of GPUs, and remained virtually unchanged. PowerTune as implemented on SI cards without Boost had 3 states – idle, intermediate (low-3D), and high (full-3D). When for whatever reason PowerTune needed to clamp down on power usage to stay within the designated limits, it could either jump states or merely turn down the clockspeed, depending on how far over the limit the card was trying to go. In practice state jumps were rare – it’s a big gap between high and intermediate – so for non-boost cards it would merely turn down the GPU clockspeed until power consumption was where it needed to be.
Modulating clockspeeds in such a manner is a relatively easy thing to implement, but it’s not without its drawbacks. That drawback being that semiconductor power consumption scales at a far greater rate with voltage than it does with clockspeed. So although turning down clockspeeds does reduce power consumption, it doesn’t do so by a large degree. If you want big power savings, you need to turn down the voltage too.
Starting with 7790 and Bonaire, this is exactly what AMD is doing. Gone is pure clockspeed modulation – inferred states in AMD’s nomenclature – and instead AMD is moving to using a larger number of full states. GCN 1.1 has 8 states altogether, with no inferred states between them. With this change, when PowerTune needs to reduce clockspeeds it can drop to a nearby state, reducing power consumption through both clockspeed and voltage reductions at the same time.
With this change state jumping will also be a far more frequent occurrence. The lack of intermediate states and the lack of granularity (8 states over 700MHz is not fine-grained) effectively makes fast state jumping a requirement, as there’s a very good chance dropping down a state will leave some power/performance on the table. So if it’s throttling, 7790 will be able to state jump as quickly as every 10ms (that’s 100 jumps a second), typically bouncing between two or more states in order to keep the card within its limits.
At the same time, AMD’s formula for picking states on non-boost cards has changed. In a move similar to what AMD has done with Richland, AMD’s temperature-agnostic state selection system has been ditched in favor of one that includes temperatures into the calculation, making it a system that is now based on power, temperature, and load. There are some minor benefits to being temperature-agnostic that AMD is giving up – mainly that performance is going to vary a bit with temperature now – but at the end of the day this allows AMD to better min-max their GPUs to hit higher frequencies more often. This also brings them to parity with Intel and NVIDIA, who have long taken temperature into account.
The fact that this is a very boost-like system is not lost on us, and with these changes the line between PowerTune with and without boost starts to become foggy. Both are ultimately going to be doing the same thing – switching states based on power and temperature considerations – the only difference being whether a card adjusts down, or if it adjusts both up and down. In practice we rarely see cards adjust down outside of FurMark, so while PowerTune doesn’t dictate a clockspeed floor, base clocks are still base clocks. In which case the practical difference between whether an AMD card has boost or not is whether it can access some higher voltage, higher clockspeed states that it may not be able to maintain for long periods of time across all workloads. The 7790 isn’t a boost part of course, but AMD’s own presentation neatly lays out where boost would fit in, so if we do see future GCN 1.1 products with boost we have a good idea of what to expect.
Moving on, with the changes to PowerTune will also come changes to AMD’s API for 3rd party utilities, and what information is reported. First and foremost, due to the frequency of state changes with the new PowerTune, AMD will no longer be reporting the instantaneous state. Instead they will be reporting an average of the states used. We don’t know how big the averaging window is – we suspect it’s no more than 2 seconds – but the end result will be that MSI Afterburner, GPU-Z, and other utilities will now see those averages reported as the clockspeed. This will give most users a better idea of what the effective clockspeed (and thereby effective performance) is, but it does mean that it’s going to be virtually impossible to infer the clockspeeds/voltages of AMD’s new states.
The other change is that with the new PowerTune AMD will be exposing new tweaking options to 3rd parties. The current PowerTune (TDP) setting is going to be joined by a separate setting for adjusting a limit called Total Design Current (TDC), which as the name implies is how much current is allowed to be passed into the GPU. AMD limits cards by both TDP and TDC to keep total power, temperatures, and total currents in check, so this will open up the latter to tweakers. Unfortunately utilities with TDC controls were not ready in time for our 7790 review, so we can’t really comment on TDC at this time. With AMD’s changes to PowerTune however (and their insistence on calling TDP thermal management), TDP may be turning into a temperature control while TDC becomes the new power control.
Finally, since these controls are going to be user-accessible, this will spill-over to AMD’s partners. Partners will be able to set their own TDP and TDC limits if they wish, which will help them fine-tune their factory overclocked cards. This will give partners more headroom for such cards as opposed to being stuck shipping cards at AMD’s reference limits, but it means that different cards from different vendors may have different base TDP and TDC limits, along with different clockspeeds. This also means that in the future equalizing clockspeeds may not be enough to equalize two cards.
Facebook
Twitter
RSS
107 Comments
View All Comments
silverblue - Friday, March 22, 2013 - link
You must've missed the part about them simply not having as much time to test the 7790 as they'd have liked because they were at GTC. Other sites apologised for their lack of time as well.There's a whole load of other reviews out there; only a few have overclocking results (Guru3D notably), and as far as I can see only AT, of the major sites, has both the 7790 and a factory overclocked 7790 in the same test. Guru3D is alone in providing a CrossFire test and though two 7790s perform about the same as a sole 670, there's no power readings. There's a good number of different titles being benchmarked so it's not strictly a list of AMD-says-test-these-titles, plus Tomb Raider, a Gaming Evolved title, performs better on NVIDIA hardware. There's a few bugs with the beta drivers used for the 7790 in these reviews most notably with latencies (a bug that has already been fixed with the next Catalyst release so yes, we will see new drivers soon), however the latency values are so far ahead on average of what we used to see from AMD that this can hardly be classed as an issue. Testing has generally centred on 1920x1080 because that's really the limit where cards like this are supposed to be performing - there's little point in 1024x768 and an equal measure of futility trying for 5760x1080 or whatever; the former is ridiculously low res and the latter is ridiculously ambitious even for a 7970 or 670/680.
Sapphire's blurb about multi-monitor usage via the TweakTown website:
"Working or gaming with multiple monitors is becoming increasingly popular, and the SAPPHIRE HD 7700 series supports this with AMD Eyefinity, now in its second generation. The SAPPHIRE HD 7790 OC Edition has two DVI ports (DVI-I and DVI-D), HDMI and a single DisplayPort output, supporting up to four monitors.
The SAPPHIRE HD 7790 OC Edition model supports the FleX feature, pioneered by SAPPHIRE, that allows three digital displays to be connected to the DVI and HDMI outputs and used in AMD Eyefinity mode without the need for an external active adapter. All four outputs can be used in AMD Eyefinity mode, but the fourth display must be a DisplayPort monitor or connected with an active adapter."
I've heard AMD's launch date for this is today; Guru3D has the following to say:
"But I need to add this little note alright; AMD's Never Settle Reloaded promotion continues. At participating retailers beginning 02 April, 2013, gamers will be able to receive a free copy of BioShock Infinite with a purchase of their new AMD Radeon HD 7790 graphics card. See, now that's great value. The Radeon HD 7790 series cards will be available in stores starting April 2, 2013"
Trusting this is of some use to you...
CeriseCogburn - Sunday, March 24, 2013 - link
I've run 2 flex edition cards, you idiot.Have you ?
Run any MDT nVidia galaxy cards dummy ?
How about all dvi outs so you daon't have to have $100's of dollars of soon to die amd dangly cables ?
Heck a friend just got ANOTHER 6870 he usually runs 4 monitors, but that could only run 2 OOB and he has loads of cables, so he had to buy another cable just to run a 3rd monitor - it took 2 weeks to arrive...
ROFL
AMD SUCKS with eyefinity / multiple monitors and nVidia DOES NOT - nVidia keeps the end user in mind and makes it INEXPENSIVE to set up 3 or 4 monitors !
Amd makes it cost prohibitive.
AMD SUCKS, they lost again, totally.
geniusloci - Saturday, March 23, 2013 - link
You are a pathetically simple little mind, aren't you?geniusloci - Saturday, March 23, 2013 - link
What planet do you come from?This card will run 4 monitors, eyefinity has done this very well, forever. With discrete audio per monitor. Nvidia is really getting handed it's ass by AMD in this category.
This card will spank it's nvidia competition in civ5, since civ uses opencl, and nvidia sucks at opencl (and their current cards even suck at cuda).
Crossfire: there's a crossfire port at the top, genius. It will obviously crossfire.
Too bad Nvidia's 2D quality and video quality is such utter shit. I might have actually used that gtx660 I bought instead of sending it back for a 7870.
CeriseCogburn - Sunday, March 24, 2013 - link
You have your display port monitor or $100 active display cable dummy ? LOL4 monitors MY BUTT.
Another clueless amd fanboy.
eric.zaba@gmail.com - Sunday, March 24, 2013 - link
You obviously dont have a clear understanding of gpu tech so just stop blabbing your stupidity, even most nvidia biased people can admit Check linus tech tips , check your games they all work much better on amd with multimonitor.and no overclock talk maybe because AMD doesnt approve of people tampering with gpus............ and because they want it to seem so good that you dont need an overclock...... and the specific hardware partners can make different port configs so why would you say that?
and maybe comparing ASUS 650tis to this GPU is invalid becuase you didnt specify who made it so the port config advantage is completely irrelevant.
Amd is not bankrupt because of their GPU business. and their CPU business isnt bad i dont think that getting into the gpu and cpu of the top 3 consoles (PS4 Xbox WiiU) is so bad either. and why would game biases not be true if amds drivers and games play better on the amd based systems
eg: Crysis 3. and saying that the civ 5 benches crashed is completely stupid because a good website like anandtech doesnt normally disregard such things. and AMD didnt pay them off if they are bankrupt right? yes it can crossfire because theres crossfire connectors on the top so maybe they assumed things would be implied for the general crowd.
althaz - Friday, March 22, 2013 - link
I think it's also worth mentioning that the 7850 is a quite excellent overclocker. At stock I think it's definitely not worth the extra $30, but once overclocking is taken into account, if you can afford the $30 you are crazy not to spend it (assuming you are comfortable with overclocking of course).Bob Todd - Friday, March 22, 2013 - link
Yeah, I'm curious what the pricing will look like on these a few weeks after introduction. I picked up a 7850 (2GB MSI Twin Frozr) for $170 AR a few weeks ago to put in a HTPC, and I've seen it at that price again already. It will be interesting to see if the regular sales on 7850s decrease once the 7790 is out. Kudos to AMD for offering BioShock Infinite with this.Aikouka - Friday, March 22, 2013 - link
Given we're talking about gaming cards here, I think it's worthwhile to add that only the 7800s and 7900s come with AMD's Never Settle game promotion. So, if you're interested Tomb Raider and/or Bioshock Infinite, the 7850 may have significantly more value to you. If you're not interested in them, people have been selling the coupons on eBay for about $50-60 each.Bob Todd - Friday, March 22, 2013 - link
There's a small paragraph in the article explaining that this card _is_ part of the Never Settle Reloaded program. It's only getting BioShock Infinite since it sits at a lower price point, but still a nice addition. The bundles are a big part of the reason I'm curious to see how the pricing shakes out. I sold a TR/BS bundle and kept about ~$50 in my pocket after fees, so I basically got a very nice 2GB 7850 for $120. You could obviously sell the BioShock code you'd get with a 7790, but if the prices for that card stay at MSRP for too long they'll have some stiff competition from 7850s on sale. Unless of course the 7850 sales dry up since it doesn't have to cover such a large swath of AMD's lineup now price wise.