More RAM for less power is forecast in 2010

WHEN LOOKING AT PC system power consumption, the usual focus is on the CPU and GPU, followed by the chipset, disk drives and such. Memory isn't considered that important in the power equation until you start putting in three or more modules and start overclocking them.

However, memory should not be ignored as the memory subsystem on a modern PC can draw 20 to 50 Watts, depending on the capacity, speed and chip generation used. In fact, 12-DIMM 96GB DDR3-1333 Nehalem Xeon workstation or server ECC memory arrays will draw upwards of 200 Watts, with the corresponding heat generation as well. At least that isn't as bad as FB-DIMMs where, according to a 2008 Microsoft server power budget survey, 128GB of FB-DIMM DDR2 memory in older Xeon systems draw nearly 350 Watts of power.

Not to mention notebook PCs, where tightly confined dense DIMMs without fan airflow are often known to reach dangerous temperatures in excess of 70C during operation. That hasn't improved with the appearance of DDR3 either, at least not yet, though battery life in notebooks will of course gain a little from the use of low voltage memory.

So, even though default memory module voltages dropped over time from 2.5V for DDR1 to 1.8V for DDR2 and 1.5V for DDR3, the current 'green' energy saving push, combined with the need for cool silent fan-free operation, has accelerated the migration to low voltage memory somewhat. Even server DDR2 memory has had 1.5V parts for two years now, with even lower voltage levels coming through the most recent 1.2V LPDDR2 specification. But the real focus is on the current cream of the crop memory standard, DDR3.

As mentioned, even at the default 1.5V and 1333 speed, DDR3 can turn quite hot in the large arrays of registered ECC modules used in workstations and servers. At the same time, DRAM process technology, with 40nm dies coming out now from firms like Hynix and Samsung, has enabled that performance to be reached with far lower voltages - 1.35V, 1.3V and even 1.2V now. When you consider that, everything else being the same, a 1.5V module will consume over half more power than a 1.2V module, with the additional heat generation thrown in as well, the benefits are obvious.

Many vendors are offering low-voltage DIMM kits now, for markets as varied as notebooks, Intel P55 home theatre silent PCs, all the way up to high-end servers. Geil in Taipei was among the first to have 1.3V certified, 1.2V capable DDR3-1333 modules, which we tested several months ago. G.Skill, also in Taipei, has come up with dual-channel and three-channel kits supporting 1.35V at up to DDR3-1600 CL7-8-7 speed, the first on desktop platforms. Many new Intel-based P55 and X58 mainboards do support lower voltages in BIOS as well.

The big vendors, like Hynix or Samsung - whose DRAM production dwarfs all of the Taiwan DRAM vendors combined - have taken the low voltage push seriously, as you can see from their slides at the Denali MEMCON conference this past June:

The cumulative savings from higher densities, better processes and lower voltages do help a lot, as you can see:

And, according to Denali Systems, a memory design expert company, the total power consumption per chip for different DRAM technologies can differ a lot. Multiply it by the hundreds of chips often seen in high end systems - compared to a maximum of 96 chips in a six DIMM three channel desktop memory setup on a Core i7 - and you can get an idea how much power saving is at stake.

What you can also notice is that the 1.2V capable DDR3 RAM, expected only a year from now, is creeping in right now. More mainboards are supporting low DDR3 voltages, too.

Keep in mind that the similar lower voltage push will happen in the graphics memory field as well, where GDDR5 can proceed to evolve both at the speed front towards 6 Gbps and towards lower power versions for single slot cards as well as in mobile GPU applications.

In summary, as most PCs will soon ship with 4GB or more memory, and most workstations and servers with upwards of 12GB, memory power consumption and cool operation will become more important. It will be acheved not just by using newer smaller process geometries, but also denser designs and, of course, lower voltage levels.

Coupled with these improved processes and densities, low-voltage DDR3 memory will help save a lot of power while still delivering up to DDR3-1600 performance, helping to improve battery life and heat dissipation across all platform types. As for the higher speeds, well the usual 1.5V and 1.65V modules will still be there for the 'enthusiast' performance realms above DDR3-2000, until DDR4, running at 1.2V by default, starts appearing sometime in 2011. µ