AMD's Dual Core Notebook : The Turion 64 X2 Part I
On May 17, 2006, AMD announced its first 64 bit dual-core laptop processors: the Turion 64 X2 series. Thanks to its two processor cores, these CPUs are capable of concurrently running several applications. This means that they substantially reduce input delays when the user switches tasks, and enable the development of much more powerful laptops. Even better, power consumption is apparently not much higher than that of its predecessor, the Turion 64. The most important new features of the Turion 64 X2 are the two processor cores and the integrated memory controller. Unlike its predecessor, the Turion 64, the memory controller supports dual-channel operation and the use of fast, power-saving DDR2 memory, resulting in a theoretical maximum memory bandwidth of 10.7 GB/s (Turion 64: 3.2 GB/s).
AMD is touting the fact they are first to market with 64-bit dual core technology for mobile processors, highlighting the fact they’ve beaten Intel to such a release. Intel will release their Merom family of dual core 64-bit processors in the August time frame:
“AMD is first to market with the only 64-bit dual-core mobile processor, driving the wave of next-generation mobile platforms that are ready today to run the upcoming 64-bit version of Microsoft Windows Vista,” said Chris Cloran, vice president, AMD Mobile Division. “This is advanced mobile technology for the office or home, packing dual-core processing for extreme multi-tasking, 64-bit computing, extended battery life and cutting-edge technology from industry leaders in wireless, connectivity and graphics.”
At first glance, the AMD architecture seems to be inferior; since each core has its own L2 cache, the two caches must synchronize their work, a process that costs time and performance. AMD has apparently adopted the cache management of the Alpha processor, however, which allows a core to query the status of a cache cell of the other core over the snoop channel without slowing down the remaining data transfer.
In any case, fewer transistors consume less power. The L2 cache of the Turion 64 X2 is only half or a quarter of the size of the Core Duo cache, so the power consumption of AMD's dual core is only slightly higher than that of the mobile Intel competitor, if at all. The reason why power consumption may be higher is that, according to Intel, unused parts of the L2 cache are disabled, which should cut power usage considerably. After all, the cache alone accounts for fifty-odd percent of the entire die surface of the processor, and power consumption is a function of the number of transistors used.
Unlike its competitor, AMD's Turion 64 X2 mobile platform is open: the chipset and WLAN components are not made exclusively by AMD, but come from renowned manufacturers like ATI, nVidia, Airgo, Atheros and Broadcom. However, this won't be the case for long, as ATI is reported to be joining the AMD fold shortly...
Be that as it may, ATI offers two chipset variants for Turion 64 X2 laptop processors: the Radeon Xpress 1100 and 1150. nVidia's portfolio features a combination of nForce Go 430 MCP and GeForce Go 6150 IGP for these CPUs. Both chipsets have integrated graphics cores.
Of course, a blog won't answer the question of whether AMD's Turion 64 X2 with ATI's Radeon Xpress 1100 chipset can challenge the Intel technology based on Core Duo and the 945GM chipset, in terms of battery life and performance. Therefore, in keeping with tradition, THG decided to compare old with new, pitting the old Turion 64 against the new Turion 64 X2 and the competition.
The processor's clock generator delivers a base rate of 200 MHz; the CPU clock rate is generated from this base rate using an integer multiplier. For example, the multiplier 10 delivers a frequency of 2000 MHz on the Turion X2 TL-60. However, in line with JEDEC's DDR2 specification, the SO-DIMM memory modules of the laptop and the associated interface currently only support maximum rates of 400, 533, or 667 MHz.
To make sure that the RAM and the interface comply with the specification, the high CPU clock rate must be reduced by a frequency divider. In the case of the Turion X2 TL-60, the divider is 6 for DDR2-667 MHz. Accordingly, the memory is operated at 333 MHz in line with the specification.
However, not every Turion 64 X2 CPU has a divider that enables operation of the installed memory with the specified clock rate. Therefore, the actual memory clock rate may be much lower than specified. For example, a Turion 64 X2 TL-56 used with DDR2-667 SO-DIMMs delivers a real memory clock rate of only 300 MHz (DDR2-600 MHz). Ultimately, the CPU selects the divider and the memory clock rate on the basis of the memory module's SPD data transmitted by the BIOS.
