DRAM Almost as Fast as SRAM

An anonymous reader writes "IBM said it has been able to speed up the DRAM to the point where it's nearly as fast as SRAM, and that the result is a type of memory known as embedded DRAM, or eDRAM, that helps boost the performance of chips with multiple core calculating engines and is particularly suited for enabling the movement of graphics in gaming and other multimedia applications. DRAM will also continue to be used off the chip."

Comments

eDRAM is quite old

[Rolman]

I don't get why this is news. Embedded-DRAM has been in heavy usage for many years now.

Both the title and the summary are quite misleading, since eDRAM is on-chip and that of course is much faster than external off-chip memory, be SRAM, DRAM or whatever.

Some big examples? PS2, Nintendo Gamecube, Wii, Xbox 360. All these consoles use eDRAM for their GPU's on-chip framebuffers to enhance their performance, and that goes back to at least the year 2000 when the PS2 came out.

Some will be quick to say "no, the Nintendo consoles use 1T-SRAM, not DRAM". Yeah, right, but even 1T-SRAM (despite its name) is a form of embedded-DRAM.

Great for L3 caches

[flaming-opus]

There are 2 areas of latency for a cache, the first is the performance of the actual data cells, and the second is the speed of doing a lookup in the cache. The larger the cache, and the higher the degree of set associativity, the longer the lookup takes. Thus you're unlikely to see this eDRAM used for L1 caches, and probably not for L2 caches either, as more cache would slow them down, even if the cells are just as fast as SRAM. The sweet spot will probably be for L3 caches, that are already slow by cache standards, but a whole lot faster than system memory. Since L3 caches are large, the cost savings for switching to eDRAM would be largest there.

As for power concerns, DRAM is higher than SRAM, but a larger L3 cache may reduce the traffic through the memory controller, and out to the DIMMs, which will probably more than make up for any increase in power density in the cache.

Re:What's the point?

[joto]

Most likely, ten years from now 80GB flash drives will be common place enough and not super expensive. But until then, spinning platers!

I expect to see 80GB flash drives long before 10 years. Assuming a growth rate of doubled capacity every 18 months, true enough, we'd reach about 80 GB in 10 years, but so far, flash memory has increased much faster than Moores law. Also I assume that the amount of data our computers manipulate continue to increase with each version of windows/HD-DVD/whatever, so we still need larger/slower storage mediums in 10 years, such as harddisks.

In fact, the whole idea of using a (set of) rotating platter(s) with magnetic coating and radially movable read/write head(s) for storage, has been so successful for so long, and continue to improve at such an astonishing rate, that I doubt it will go away any time soon. In the far future, it's more difficult to predict what would happen. But even today, wheels are important, fire is our main source of (non-food) energy, primitive cutting tools are regulary used in any household, and in general, assuming things fail to change, is rarely wrong (we still haven't got flying cars!)