ASUS HD 7790 Direct CU II OC 1 GB Review

Introduction

AMD announced its first new desktop graphics product of 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 gives 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 they aptly priced at $149 (now $139). The HD 7770 GHz Edition may convincingly beat the GTX 650 (non-Ti), but isn't powerful enough 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 works 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 dividend 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 results in 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 to switch the clock speed, as needed, between 8 power states.



In this review, we're testing the ASUS HD 7790 using the company's famous Direct CU II cooler. The card uses a close-to-reference design 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.