For some time there has been a growing disparity between processor power and memory capacity. As processors and systems have become more computationally dense, memory capacities have been growing more slowly. This has been less of an issue in PCs, where both compute power and memory are relatively abundant, but as high performance computing, virtualization, and large transactional databases take hold in the datacenter, memory has increasingly become the bottleneck to system performance. While lack of memory bandwidth may be the ultimate constraint for maximum CPU performance, for memory-constrained applications, sufficient RAM is required just to get past the formidable disk bottleneck.

Unfortunately scaling memory is not nearly as simple as scaling processing power. An economic discontinuity exists in the DRAM market. While 1 Gbit DRAM chips cost around $3, a 2 Gbit DRAM chips cost $30 to $50 dollars. And since commodity systems with DDR2 memory controllers are designed with only a limited number of DIMMs (which themselves contain a fixed number of DRAM chips), the only way to get more memory is to go with the outrageously expensive 2 Gbit chips. Since the memory controllers are designed to talk with a limited number of DRAMs, this effectively limits affordable capacity.

But MetaRAM, a 2-year-old fabless semiconductor startup, is attempting to change the game. Last week, the company unveiled a new product line that is able to aggregate 1 Gbit DRAMs so as to increase affordable main memory by a factor of two to four. The 34-person company has developed new memory technology — called MetaSDRAM — that allows 8GB and 16GB DIMMs to be built from low-cost 1 Gbit memory components. According to the company, a four-socket server can be populated with 256 GB of MetRAM memory for only $50,000. Using conventional DDR2 memory, this same system would cost $500,000 — $480,000 of which is just DRAM.

The new MetaRAM device contains a special chipset that virtualizes the 1 Gbit components so that a DDR2 memory controller thinks its talking with 2 Gbit or 4 Gbit DRAMs instead of multiple 1 Gbit DRAMs. (Fortunately, the memory controllers aren’t smart enough to know that 4 Gbit DRAMs don’t even exist yet.) Internally, the 1 Gbit DRAMs think they’re talking directly with the memory controller. The chipset in the middle contains the smarts to do the needed DDR2 protocol translations and keep the memory accesses coherent.

“So we look like a DRAM to the memory controller, and a memory controller to the DRAM,” says Suresh Rajan, MetaRAM VP Marketing.

Rajan and CEO Fred Weber founded MetaRAM in January 2006 with the idea of leapfrogging the “memory capacity gap.” Weber, a former CTO at AMD who helped drive the 64-bit x86 revolution at his former company, saw the new opportunity in the processor-memory disparity and decided that the growth of Web 2.0, datacenter virtualization, and high performance computing were going to create a large demand for x86-based systems with much larger memory footprints. In the HPC realm, memory-hungry applications in aerospace/automotive, financial services, digital content creation and rendering, oil and gas exploration, and semiconductor design and simulation would especially benefit from lots of RAM.

“Where this really gets exciting is that we can build very powerful clusters at very affordable prices to solve problems that are memory bound,” says Rajan. “Obviously some applications are compute bound, but others are memory bound, and for the latter, this is a great technology.”

The first two MetaRAM products announced are the 8 GB and 16 GB R-DIMMs. The 8 GB chipset is currently in full production and is available for $200 , while the 16 GB is qualified, but not yet in production, and will be priced at $450. Hynix Semiconductor and SMART Modular Technologies have partnered with MetaRAM to produce the memory modules for system vendors. Hynix is a large semiconductor manufacturer with relationships with many of the tier one OEMs; SMART Modular is focused on the tier two players, plus system builders and other channel customers.

Server/cluster vendors that are currently committed to carrying the first 8GB DIMMs include Appro, Rackable, Colfax International and Verari. System availability is expected in Q1 of this year, that is, any day now. Rajan says they’re talking with all the usual HPC system vendors, and he says we can anticipate more OEMs to announce MetaRAM support at some point. He notes that they currently have a working eight-socket Opteron Sun machine in-house with 512 GB of MetaRAM memory.

Some OEMs might be resistant to offering high-memory servers at commodity pricing, since this might cut into their high-end server margins. But if more system vendors offer MetaRAM-based systems, it would be difficult for their competitors to resist, especially in the highly price-sensitive x86 server market.

The MetaRAM chipset is plug compatible with any DDR2-compliant memory controller and has been qualified for both Opteron and Xeon chipsets. Currently, the MetaRAM hardware will end up mostly in AMD Opteron-based systems, since DDR2 memory controllers are standard issue there. Intel’s relatively new 5100 MCH chipset also supports DDR2, and as time passes, more Intel chipsets are likely to switch from the power-hungry, higher latency FB-DIMMs, to parallel DDR2 memory. The original idea behind the FB-DIMM was also to provide higher capacity memory, but high power usage, added latency and chipset inflexibility have proven barriers for more widespread industry adoption.

The MetaRAM technology had to overcome a few challenges as well. The chipset does add some additional latency compared to directly connected DDR2 memory. But according to MetaRAM tests, latency increases only a percent or two in a four-socket system — much less than an FB-DIMM. For memory-bound applications, the company expects any small rise in latency to be dwarfed by an average increase of between 20 and 30 percent in overall performance.

The biggest hurdle that the MetaRAM had to address was power usage. By doubling or quadrupling the number of 1 Gbit DRAMs on the DIMM and adding the extra chipset, they had to find a way to keep power usage in the same neighborhood of a low-memory DIMM. This is accomplished via their “WakeOnUse” technology, which sends power only to DRAM elements that are being accessed, while putting the rest of memory to sleep. It’s a little like turning the lights on in a house as someone walks from room to room, while switching off the lights in the remainder of the house. Rajan claims this yields about 30 percent greater power-efficiency on a watts per gigabyte basis.

According to Weber and Rajan, the MetaRAM technology accelerates affordable memory capacity by two to four years, and will ride commodity memory to stay ahead of the curve. While 1 Gbit DRAMs currently represent the best price-capacity memory today, by 2010, 2 Gbit DRAMs will be the volume solution, and by 2013, 4 Gbit devices should start to show up. MetaRAM also intends to modify the chipset to support DDR3 memory, when that technology goes mainstream.

“I think for the next five to eight years, we see a clear path ahead of us,” says Rajan. “It is our belief as time progresses that our technology will become more and more critical for the server market.”