MetaRAM quadruples DDR2 DIMM capacities, launches 8GB DIMMs

Since its launch in January2006, the only thing that has been publicly known about former AMD CTOFred Weber's new venture is its name: MetaRAM. Clearly, thestealth-mode company was working on something to do with RAM, but what?As of today, MetaRAM is finally ready to talk about its technology, andit appears to be a pretty solid evolutionary step for thetried-and-true SDRAM DIMM module. In short, MetaRAM's technologyenables DIMM capacity increases of two or four times, so that a singleDDR2 MetaSDRAM DIMM can hold 4GB or 8GB of memory while still being adrop-in replacement for a normal DIMM.
Because MetaRAM'shigh-capacity DIMMs look to an Intel or AMD system like normal DDR2DIMMs, the company expects to see servers with memory configurationsthat would normally require expensive custom hardware to becomesignificantly cheaper. One of MetaRAM's channel partners will soonannounce a server with 256GB of main memory for under $50,000, with500GB boxes on tap for a higher price points
I'm tempted tosuggest that "500GB of memory oughta be enough for anybody," butMetaRAM is looking to virtualization and enterprise databases asapplication domains that provide a rationale for putting that muchmemory in a single server. MetaRAM claims that its own researchindicates that 80 percent of enterprise server databases are under500GB in size, and if this is true, then hosting those databasesentirely in main memory could get a lot cheaper after today.
MetaRAMis a fabless semiconductor company, and its manufacturing partners areHynix and SMART Modular. Both chipmakers are currently sampling 8GBDDR2 DIMMs, and MetaRAM expects to see servers and workstations thatinclude the technology available from Rackable and launch partnerslater this quarter.
How it works
MetaRAM uses a 3D chipstacking technology to cram extra SDRAM chips onto the DIMM, with theresult that each DIMM is actually two or four DIMMs worth of memory.Also on the DIMM is a pair of custom chips that are the secret saucethat makes MetaRAM work. This MetaRAM chipset sits in between thesystem's main memory controller and the on-DIMM DRAMs, routing readsand writes to the appropriate DRAM and hiding its own presence.
"Wehad to make our chip look like a DRAM to the memory controller, andlike a memory controller to the DRAMs," said Suresh Rajan, the MetaRAMco-founder whom I talked to about the company's technology. This memorytraffic routing messes with the DDR2 DRAM timings quite a bit, so theMetaRAM chipset's dynamic command scheduling circuitry ends up doing akind of "out-of-order execution" with the flow of reads and writes sothat the DIMM can operate at a full 667MHz without any glitches.

A MetaRAM DIMM

Rajanclaims that in order to squeeze its chipset into the standard DIMMpower and thermal envelope, the company had to do a fully customcircuit design. "Ever single cell in the chip was hand-placed andhand-routed to make sure that the clocking fits with existing systems,"said Rajan.
Also important in enabling MetaRAM to meet itsstrict power budget is the company's WakeOnUse technology, which worksas follows: a MetaSDRAM DIMM tries to keep all of its on-board DRAMsasleep if possible, and since the MetaRAM chipset is constantlydirecting memory traffic, it has a good idea of where the next readsand writes will come from and which SDRAMs it should wake up. Thisdynamic power optimization, where SDRAMs are only awakened if they'reabout to be used, is key for keeping a MetaSDRAM DIMM within normalDIMM constraints.
I asked Rajan to compare and contrast MetaRAMwith FB-DIMM in terms of power draw, and he told me that the typicalFB-DIMM's AMB draws 5 to 7 watts. The MetaRAM chipset, in contrast,draws only 2.5 watts on the high end, and the power draw scaleslinearly with usage.
Ultimately, MetaRAM looks like a solidreplacement for FB-DIMM. Sure, you're stuck with DDR2's bandwidth, butas a consolation prize you get a ton of extra capacity with the samepower envelope and interface as regular DDR2 SDRAM. It's likely that aserial, packet-based memory protocol (a la RDRAM or FB-DIMM) is stillin our future, but MetaRAM looks poised to tide us over nicely untilthat future arrives.