As we predicted in a recent article dealing with AMD’s new graphics cards from the HD 7000 series, after the high-end models were presented, miniature chips would follow, replacing the very popular Juniper-based products. The Juniper GPU “survived” for two Radeon generations, which is mostly due to its unprecedented success, one that’ll be hard to repeat, if there even is the need for such a thing.
This GPU first saw the light of day on Radeon HD 5770, making a re-appearance a year later on the rebranded Radeon HD 6770. NVIDIA never really came up with a proper response to these two cards. The first time around, they tried to compete with GTS 450, which wasn’t even nearly adequate for such a battle. GTX 550 Ti did a little better, but the latter was still slower by a good 10%.
This wouldn’t have been a problem had GTX 550 Ti been cheaper than its competitor, but not only did it lose in the performance field, it fared similarly in the retail one too. More ambitious companies such as ASUS tried to rectify this situation by putting high-quality cooling and factory-overclocked models out on the market, with products such as the TOP series. Yet even a heavily tightened GTX 550 Ti, with core clocks of up to 1 GHz, couldn’t do anything. Up to this day, Radeons HD 5770 and HD 6770 have remained in widespread use due to their good performance, but it’s now time for them to retire and be rightfully replaced by an adequate heir. The chip taking the price/performance throne from Juniper is codenamed Cape Verde, and we have to admit that expectations are very high from both models it’s featured on.
So, what’s inside the very exotically named Cape Verde chip? Well, like Tahiti, it’s manufactured in TSMC’s 28 nm production process. The new lithography enables a larger amount of transistors to be placed on a relatively tiny surface, quite logically. Cape Verde shares the same genetics with Tahiti in terms of technology, therefore. This also means that all features seen in AMD’s high-end chip also apply here, with the only difference being Tahiti’s raw processing power which Cape Verde cannot hope to match.
Naturally, this implies good gamma segmentation too, and the two Cape Verde models are supposed to fill the gap in the 100 to 200 dollar-range; in other words, expect them to retail at around 75€ and 160€ in Europe. As far as technology goes, Cape Verde hasn’t missed a thing, having full support for DirectX 11.1, Shader Model 5.0, as well as OpenGL 4.1. Graphics cards based on this chip have all renditions of Eyefinity 2.0, but also HD3D. Even multiple audio streams are supported, which is truly excellent, and we’re of course referring to DDMA (Discrete Digital Multipoint Audio).
Using this system, Radeons are able to play entirely different audio for each monitor in an Eyefinity configuration. This also requires support for the latest video outputs, such as HDMI 1.4a and DisplayPort 1.2 (HBR2), present on both these mid-range models. Although this GPU isn’t such a large consumer of energy, AMD has equipped it with ZeroCore technology, first seen when testing HD 7970. As a reminder, the ZeroCore technology works so that practically all components of the graphics card are put in a sleep mode when the card is idle for longer periods of time; only vital elements, crucial to graphics card operation and detection in the OS, remain powered. This is colloquially called “long idle mode”, amounting to just a few watts of power. Although all Radeons in this class will be very power-efficient, the fact that they still have this feature says a lot about AMD’s resolution not to leave out users with shallower pockets out of the equation – every AMD user has the right to the same technology in a product generation, with the only difference being the one in performance, which is a concept we salute.
The Cape Verde chip has 1.5 billion transistors, which is a definitely a lot, enough to make even top-notch graphics chips from a few years ago shy away. Still, it doesn’t tell you a whole lot about the graphics performance simply because much of this number falls off on numerous Tahiti technologies that have been kept here as well. Therefore, don’t be surprised if we tell you that the entire Cape Verde GPU only has 640 stream processors. Hey, didn’t Juniper have 800 of these? You’re right to ask yourself that question, because we did too. Of course, the new NCG architecture is more efficient than the old VLIW5, but that doesn’t change the fact that users are going to be suspicious towards the new GPU. Simply put, even Tahiti has managed to pack more stream processors compared to Cayman, and we expected the same from Cape Verde.
These 640 stream processors are split into clusters of 64, giving a total of ten clusters, but more importantly, implying that AMD will be able to use partially dysfunctional chips for weaker models. Besides the stream multiprocessing units, there’s also the latest-gen tessellation unit, as well as a largish quantity of L2 cache memory of 512 KB. The number of ROP and texture units has remained unchanged compared to Juniper, with 16 and 40 in the full-blown version, respectively. We have to admit that, although we’re impressed by the fact that Cape Verde has all current technologies, we’re not too impressed by its technical specifications.
We’re fully aware of the advancements of the new technology and the fact that optimisation will provide high enough performance to surpass an HD 5770, but we just don’t think that this was the way to go for AMD. This sort of reasoning requires the lacking number of stream processors to be matched by higher clocks (as we’ll see later on). We received the first two models from AMD directly, providing us with HD 7770 and HD 7750.
AMD Radeon HD 7770 1 GB
HD 7770 is the strongest model with the Cape Verde chip, fully functional and with no sections locked, so it’s hard to imagine even better products based on this GPU appearing later on. The first thing you’ll notice on Radeon HD 7770 is the cooler design, combining black and red. In terms of looks, it’s almost like a miniature version of HD 7970. Still, some changes do exist, mostly in the fan section, which is of common, not turbine shape.
Kudos to AMD for this choice, as this also means less noise, a pet peeve of ours since our encounters with HD 7970 and HD 7950. This red fan has a diameter of 80 mm and carries the logo “1 GHz edition”, which confirmed our suspicions that HD 7770 will try to hide its weaker specs with increased clocks.
A large black aluminium cooling body is hiding below the plastic shield. With such a low TDP of just 80 W, we weren’t really expecting anything fancy and complex as cooling solution. Everything’s kept in check just by this aluminium cooling body, with no need for heatpipes or copper pieces in the cooler base etc.
The power section for a small chip shouldn’t be too complex either, and it isn’t, having a 3+1 phase configuration. The PCB is black and contains not only the Cape Verde GPU, but also four memory chips. This is GDDR5 memory, of course, forming a 128-bit bus, which, paired with a frequency of 1125 MHz (effectively 4.5 GHz) gives a throughput of a very high 72 GB/s. It’s perhaps interesting to note that HD 5770/6770 betters the new product even in this segment, with 76.8 GB/s, although it’s an academically small difference overall. Despite being declared to only 80 W of power consumption, the card still has a 6-pin molex connector, and the interface it supports for main power supply and communication is the third-gen PCI Express.
Just like earlier models in this price range, Radeon HD 7770 also has a CrossFireX connector, enabling it to connect two cards into a multi-GPU system, and we’re definitely interested in seeing how well performance will scale with this generation of mid-range Radeon cards. CrossFireX is a concept that has seemed more and more viable and efficient as years passed, coming very close to 100% efficiency in a few cases, so here’s to hoping that the HD 7000 series will bring further advancements in this respect.
As far as video outputs go, it’s clear from the get-go that you won’t be falling behind Tahiti owners in any way. There’s one DVI and one HDMI 1.4a connector, as well as two mini-DisplayPorts, which grants you great flexibility when running an Eyefinity configuration. As previously stated, HD 7770 has a fully functional Cape Verde GPU, which means that it has the maximum 640 stream processors, 40 texture and 16 ROP units.
In accordance with the label on the fan, the factory clock for the GPU is an entire 1 GHz. It’s interesting that this is the first graphics card ever to have a default clock of 1 GHz. We haven’t received a reply to the question if there will be lower-clocked models on the market – AMD has simply stated that this was the recommended default clock for any model, and manufacturers will have the liberty of amending it both ways.
It should also be noted that Radeon HD 7770 has a native voltage increase solution, which makes its overclock margin much higher according to the company. That’s it for the moment; let’s have a look at the weaker brother now.
AMD Radeon HD 7750 1 GB
The second card we received for testing is noticeably simpler, and by noticeably we really mean painstakingly obviously. Compared to the “fatty” Radeon HD 7770, its younger brother has a tiny aluminium cooling profile which doesn’t occupy the adjacent slot. Simpler cooling implies a more “relaxed” GPU too, and the PCB is shorter by approximately a third as well.
The power section has a 2+1 phase configuration, and HD 7750 doesn’t even have a CrossFireX connector. All this is very interesting for AMD, as differences between HD 5770 and HD 5750 were much more subtle, while there’s a clear distinction between two mid-range models this time. The fan is of standard shape, but with a diameter of only 50 mm, which is immediately associated with a higher RPM and consequently higher noise levels. Under the cooler, there’s the already familiar Cape Verde GPU, but with the number of stream multiprocessor units reduced by two, giving a chip “shorter” by 128 stream processors compared to the full-fledged version.
Therefore, HD 7750 has 512 stream processors at disposal, but owing to the NGC architecture which ties the ROP units to the memory bus, the number of ROPs has remained at 16, which means a great deal in saving performance levels. Still, as each block has four texture units, and HD 7750 has two fewer blocks than HD 7770, the total number of texture units is 32.
Core clock is also noticeably reduced, to 800 MHz, and since any kind of additional power connector is entirely absent, the overclock margin isn’t something to be counted on; the weaker power section only contributes to this. Yet contrary to our expectations, the memory subsystem has been left untouched compared to the previously described model – Radeon HD 7750 has four 256 MB GDDR5 memory chips and a 128-bit bus at disposal.
The memory clock is declared to an identical value, 1125 MHz, or effectively 4.5 GHz. Honestly, we’re not too sure how much benefit this card will have from such a high memory bandwidth, as the weakened Cape Verde can hardly use it.
Then again, HD 7750 is targeted at less demanding users anyway, which is visible both in its specifications and its meagre TDP of only 55 W. As far as video outputs go, HD 7750 had to be impoverished, but not as much as one would think. All current video output standards are featured, even if only one each: one DVI, one HDMI and one DisplayPort connector. The latter comes in full, not mini-size.
Specifications and Results
|GPU Clock [MHz]||1000||800|
|No. of Stream Processors||640||512|
|ROP / Texture Units||16 / 40||16 / 32|
|Memory type / capacity / bus widith||GDDR5 / 1GB / 128||GDDR5 / 1GB / 128|
|Memory clock / effective clock [MHz]||1125 / 4500||1125 / 4500|
|Results||AMD Radeon HD7770 1GB||AMD Radeon HD7750 1GB||Gigabyte GTX550 Ti 1GB||ASUS HD6770 DirectCU 1GB|
|1680x1050 / 1920x1080 0xAA 0xAF|
|3DMark 11 (performance preset) GPU Score||2.233 / 1.631||1.599 / 1.201||1.632 / 1.247||1.787 / 1.360|
|3DMark Vantage (high preset) GPU Score||9.968 / 8.664||6.396 / 7.333||8.133 / 7.095||7.427 / 6.465|
|Unigine Heaven 2.5 (DX11, medium, tesselation) [fps]||37,9 / 34,1||36,3 / 32,1||27,3 / 24,1||24,9 / 21,9|
|Crysis Warhead (DX10, Gamer) [fps]||46,9 / 41,4||36,6 / 32,1||38,8 / 33,9||39,6 / 34,7|
|Crysis 2 (DX11, Ultra, HD Textures) [fps]||44,3 / 38,7||34,1 / 28,8||36,6 / 31,4||37,3 / 32,4|
|Metro 2033 (DX11, high, tesselation) [fps]||43,1 / 38,8||32,6 / 36,3||35,7 / 31,9||36,5 / 32,7|
|AvP DX11 (DX11, max) [fps]||37,2 / 42,1||29,1 / 25,6||36,8 / 32,7||38,6 / 34,1|
|F1 2010 (DX11, max) [fps]||45 / 42||36 / 33||32 / 30||38 / 35|
|Dirt 3 (DX11, Ultra) [fps]||47,3 / 42,9||32,7 / 28,6||40,2 / 35,9||40,8 / 36,7|
|Lost Planet 2, Test B (DX11, high) [fps]||39,1 / 36,2||30,5 / 28,3||30,9 / 27,2||27,9 / 28,7|
Overclock and impressions
As AMD has equipped Radeon HD 7770 with the option of software-controlled GPU voltage, as well as a pretty good cooling system, we were expecting a lot in terms of overclocking this card. The fan was very quiet at default frequencies, as well as on manual settings up to 50% of the maximum RPM rate.
Temperatures were rather low, reaching a peak of 71 degrees, while the fan didn’t need to seriously intervene at any one time, sticking to its low default speed and keeping things silent. After fixing its speed to 50% manually, which was our internally established max, we ventured after the overclock margin and optimal voltage settings.
The result was 1200 MHz, but only because that’s the limit allowed by Catalyst’s Control Centre, and with a voltage of 1.3 V! This is an excellent result, and we’re positive that the GPU can do even better in unrestricted conditions. The memory was a team player too, reaching up to 5 GHz with no sweat. At these clocks, we gained about 10% in performance, which may not look like much, but is more than we had expected.
Radeon HD 7750 isn’t the same success story, as the card itself is much more limited in nature. We only reached 860 MHz from the starting point of 800 MHz, with everything higher resulting in tests crashing.
The memory fared a little better, but this hardly impacted the results, as the weakened GPU can hardly use the default memory bandwidth as it is. Heating remains low at all times despite a simple cooler, and a peak of 67 degrees after extensive testing is definitely laudable.
The Cape Verde test has been a streak of positive impressions on the whole, but some key things left a lukewarm feeling. On one hand, it’s fascinating that AMD has managed to provide all possible technologies to the mid-range, leaving out nothing compared to Tahiti chips.
Another commendable fact is that AMD has managed to present customers with a 28 nm mid-range GPU while the competition has yet to roll out anything in this production process. With all that, cards work just as expected at their worst, and magnificently at their best – HD 7770 is mindbogglingly overclockable. The only piece of the puzzle we’ve expected more from is the number of stream processors; it’s as if AMD failed to realise that Cape Verde has to be a good enough heir to Juniper as the king of mid-range graphics cards.
Fact that the competition hasn’t managed to match the price/performance ratio of HD 5770 and HD 6770 to this day says a lot about how well-balanced these cards are. That said, although it’s definitely faster than these two, HD 7770 doesn’t really achieve the performance gain we’d hoped for, falling into the 15-20% margin; a respectable result, but insufficient to repeat the success of Juniper in our opinion especially considering the fact that it is almost double in price
. Furthermore, it could easely happen that the competition won’t have such a hard time matching its performance this time around, and that Cape Verde won’t be the long-lasting performance champion Juniper was. Finally, we think that AMD is a bit rampant with the prices, using the advantage it has gained over the competitor with such an early presentation of the new generation of cards, so we’re expecting these initial Cape Verde prices to fall quite a bit over time.
The final call is that Radeon HD 7770 and HD 7750 are definitely good, no, great products, but unlikely to repeat the success of their predecessors. In the end, they will probably end up in the lower price segment, and will get replaced by for e.g. HD7830 or HD7850.
In that spirit, if you already own the HD5770 or HD6770 don't rush to buy a new model, but if you are more than two generations behind you might as well get HD7770 end enjoy new AAA titles in high definition on card that can easily fit anyones budget.