Sapphire HD 7790 Dual-X 1 GB

Sapphire HD 7790 Dual-X 1 GB

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Introduction



AMD announced its first new desktop graphics product for the year, the Radeon HD 7790. The company recently made it clear to us that it won't be introducing a new GPU family any time soon, at least not before October, but that doesn't mean it can't do patchwork to its existing product stack. The company seems least bothered with NVIDIA's recent GTX Titan Launch and finds that its "Never Settle Reloaded" bundles give its products an edge over NVIDIA's offerings, and with a bouquet of game titles under development that are optimized for its GPUs, things look like smooth sailing. In all the noise, AMD conveniently neglected the sub-$200 market.



The $100-200 market segment is a particularly high-volume one. AMD's current offerings include the Radeon HD 7850 1 GB around $179, the Radeon HD 7770 GHz Edition at $109, and practically nothing in between, unless you want to buy near-EOL new old-stocks of previous-generation AMD offerings such as the Radeon HD 6870. NVIDIA targeted this gap with its GeForce GTX 650 Ti aptly priced at $149 (now $139). The HD 7770 GHz Edition may convincingly beat the GTX 650 (non-Ti), but is too underpowered in comparison to the GTX 650 Ti. Playing current games at 1080p using the HD 7770 is asking for much.

AMD finally got down to do the patchwork, but may have realized that its 2.8 billion-transistor "Pitcairn" GPU can't be sold at price points lower than what the HD 7850 1 GB commands, and it could certainly not offer any cushioning for further price-cuts. AMD's solution? Build "Bonaire," a spanking new ASIC with just 2.08 billion transistors, but with a clever component layout. The chip allows AMD to price the Radeon HD 7790 exactly at $149, with room for future price-cuts.



Built on the 28 nm silicon fab process, Bonaire's component hierarchy has more in common with "Pitcairn" and "Tahiti" than with "Cape Verde," although all four are based on AMD's Graphics CoreNext micro-architecture. It features 14 compute units, which work out to 896 stream processors, two independent geometry engines, and two rasterizers. In comparison, Cape Verde may have 10 compute units (640 stream processors), but just the single geometry engine and rasterizer. AMD's approach with Bonaire may yield dividends with tessellation performance, so enabling tessellation shouldn't tax the GPU as much. AMD didn't widen the memory bus any further than 128-bit, but took advantage of falling 7 GT/s chip prices to clock the memory at 6.00 GHz (GDDR5 effective), which yields 96 GB/s of memory bandwidth (a 33% increase). The core remains at 1.00 GHz, but is augmented with an improved dynamic clock technology.



The new dynamic clock technology, which AMD no longer refers to as "boost," promises higher sustained clock speeds and better energy efficiency. The core clock speed mentioned by AMD in its specs sheets, 1.00 GHz, is the GPU's maximum (unless you manually overclock), which most applications shouldn't have a problem accessing. An improved dynamic-clock algorithm gauges graphics processing load, power limits, and temperatures at a higher polling rate of 10 ms, switching the clock speed, as needed, between 8 power states.



In this review, we're testing Sapphire's premium implementation of the Radeon HD 7790 featuring the company's Dual-X cooling solution. The card features a custom-design dual-fan cooler and offers factory-overclocked speeds of 1075 MHz core and 6.40 GHz memory for a premium of just $10 over AMD's suggested reference design retail price of $149.

Radeon HD 7790 Market Segment Analysis
 Radeon
HD 6850
Radeon
HD 7770
GeForce
GTX 460
GeForce
GTX 650 Ti
GeForce
GTX 560
Radeon
HD 6870
Radeon
HD 7790
Sapphire Radeon
HD 7790
GeForce
GTX 560 Ti
Radeon
HD 6950
GeForce
GTX 570
Radeon
HD 6970
Radeon
HD 7850
GeForce
GTX 660
Radeon
HD 7870
Shader Units96064033676833611208968963841408480153610249601280
ROPs321632163232161632324032322432
Graphics ProcessorBartsCape VerdeGF104GK106GF114BartsBonaireBonaireGF114CaymanGF110CaymanPitcairnGK106Pitcairn
Transistors1700M1500M1950M2540M1950M1700M2080M2080M1950M2640M3000M2640M2800M2540M2800M
Memory Size1024 MB1024 MB1024 MB1024 MB1024 MB1024 MB1024 MB1024 MB1024 MB2048 MB1280 MB2048 MB2048 MB2048 MB2048 MB
Memory Bus Width256 bit128 bit256 bit128 bit256 bit256 bit128 bit128 bit256 bit256 bit320 bit256 bit256 bit192 bit256 bit
Core Clock775 MHz1000 MHz675 MHz925 MHz810 MHz900 MHz1000 MHz1075 MHz823 MHz800 MHz732 MHz880 MHz860 MHz980 MHz+1000 MHz
Memory Clock1000 MHz1125 MHz900 MHz1350 MHz1002 MHz1050 MHz1500 MHz1600 MHz1002 MHz1250 MHz950 MHz1375 MHz1200 MHz1502 MHz1200 MHz
Price$135$120$140$140$170$170$150$160$200$170$250$380$180$215$220
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