I’ve been waiting for this: water-cooled DDR3 SDRAM from Kingston

Long, long ago in a galaxy far, far away--PC motherboards carried an array of chips including a microprocessor and memories and none of those motherboard chips sported a heat sink. That was way, way back in the mid 1980s. Processor speeds gradually climbed from the original 4.77 MHz to tens and then more rapidly into hundreds of MHz finally attaining GHz clock rates. Along the way, processors strapped on heat sinks, then fan sinks, and now liquid-cooled heat sinks. Similarly, all of the other chips on the motherboard coalesced into Northbridge and Southbridge chips that eventually sported heat sinks, then fan sinks, and now the top gaming computers use liquid-cooled heat sinks for these chips as well. So it shouldn’t be much of a surprise that DRAM is traveling along precisely the same path.

DRAMs jumped from the motherboard to SIMMs and then DIMMS starting in the late 1980s. I remember creating a half-length memory board for the PC bus that was based on AST’s 2Mbyte board as a surface-mount project for EDN magazine back in 1987. I used eight 256-Kbyte (!) SIMMs to fit two Mbytes of DRAM on a half-length expansion board. At the time, AST’s founders seriously asked “Who would use SIMMs when the individual chips are cheaper and can easily be fit onto a PC motherboard or a full-length expansion card?” These days, that’s not even a remotely viable question. In fact, it seems rather quaint, doesn’t it? But the point is, back then in the late 1980s DRAMs were just moving onto SIMMs and they didn’t require or sport heat sinks even though closely packed together. We would have thought the idea laughable.

Today’s fastest DDR3 memory chips mounted on DIMMs clearly do need heat sinks. You see increasingly fanciful heat sink design because gamers buy the fastest memory DIMMs available at premium prices and they want their fast machines to look cool inside and out. These fast SDRAM DIMMs consume a lot of power and they require heat sinks. They’re beginning to require fans as well, as evidenced by Kingston’s HyperX Fan, a dual fan assembly lit by blue LEDs. Very cool looking. Now Kingston has taken the expected next step, introducing HyperX H2O 2133 MHz DDR3 DIMMs with built-in fittings for liquid cooling (see photo below).
Note that SDRAM operating temperatures have been climbing primarily because of the increasing memory-interface speeds. As noted last week at MemCon 2010 by Cadence’s Marc Greenberg, the actual DRAM memory array core speeds have been stable at 100-200 MHz for years. It’s the memory interface speeds that have been rising quickly (necessitating larger and larger page sizes to compensate). As long as SDRAM continues to use single-ended, Volt-level signal swings, multi-GHz interface speeds will result in a fair amount of power consumption.

That situation has created an opening for the use of low-voltage, differential signaling (LVDS) for new high-speed memory interfaces as proposed by the SPMT Consortium and Rambus (Mobile XDR). Make no mistake, these more advanced interfaces are on their way. They are absolutely needed “real soon now” by the mobile and handheld product crowd and I can easily see them propagating across the board into a variety of different applications if one of the LVDS technologies gains a foothold in those application areas that must cut power consumption.