Rambus Takes Another Shot At High-End Memory

An anonymous reader writes "Tom's Hardware is running an article about Extreme Data Rate memory (XDR DRAM for short), which was developed by Rambus and now entered mass production in Samsung's fabs. Right now, Rambus says the memory is only for high-bandwidth multimedia applications such as Sony's Cell processor, but the company ultimately hopes to push XDR into PCs and graphics cards by 2006. Time will tell if Rambus has learned from the mistakes it made with RDRAM a few years ago."

Comments

Re:Why do we use DRAM in this day and age?

[be-fan]

Because SRAM takes up 6 transistors per bit, while DRAM takes up 1 transistor per bit. The biggest mainstream CPUs run about ~150m transistors, and that's only enough (if everything were cache), about 3MB.

Rambus seems to forget

[onyxruby]

Rambus seems to forget their attempt to shanghai the entire memory business through fraud a few years ago. Perhaps they should be reminded that the IT community has not. They should sell their IP and disolve themselves to avoid losing their stockholders any more money.

I have adamantly refused to purchase any system that would use their memory for years, and more to the point have made that decision for others that depend on me making that decision. That's a lot of computers over the years were talking about. I am also far from alone.

Time Will Tell?

[cacepi]

Time will tell if Rambus has learned from the mistakes it made with RDRAM a few years ago.

Well, Rambus has expanded their latest lawsuit blitz to include DDR2 patent claims, so do you think they've learned?

Re:The numbers don't lie!

[captaineo]

The test case was intensive ray tracing with Pixar's RenderMan on two systems:

3.06 GHz Pentium 4, 512KB cache, 533MHz FSB, RDRAM
3.00 GHz Pentium 4, 1MB cache, 800MHz FSB, DDR400 RAM

The DDR system is only 86% as fast as the RDRAM system (the RDRAM system is 16% faster). This is despite the DDR system having been purchased almost two years later, and having more cache!

The DDR system does pull ahead for compositing tasks (by quite a bit - in some cases it's twice as fast). I assume this is due to the larger cache.

But ray tracing takes about 90% of my total render times, so it's far more important to optimize. I am disappointed that I can't buy hardware today with the same RAM performance as I got two years ago.

Re:It will be awhile

[Moraelin]

One reason the AMD 64 works so well is precisely because they _reduced_ latency. That's basically the great advantage that the IMC (Integrated Memory Controller) offers.

Funny abstraction layers and everything being agnostic of everything else is a nice CS theoretician fantasy. In a CS theory utopia everything should be abstracted, or better yet virtualized. Any actual hardware or other implementation details should be buried 6 ft deep, under layers after layers of abstraction or better yet emulation.

The problem is that reality doesn't work that way. Every such abstraction layer, such as buffering and translating some generic RAM interface costs time. Every single detail you play agnostic about, runs you the risk of doing something extremely stupid and slow. (E.g., from another domain: I've seen entirely too many program implementations that, in the quest to abstract and ignore the database, end up with a flurry of connections just to save one stupid record.) Performance problems here we come.

The AMD 64 runs fast precisely because it has one _less_ level of abstraction and virtualization. Precisely because their CPU does _not_ play agnostic and let the north-bridge handle the actual RAM details. No, they know all about RAM, and they use it better that way.

So adding an abstraction layer right back (even if one that moves the north-bridge on the RAM stick) would solve... what? Shave some 10% out of the performance? No, thanks.

Or you mention SRAM. Well, the only advantage to SRAM is that it's faster than DRAM. Adding an extra couple of cycles of latency to it would be just a bloody stupid way to get DRAM performance out of expensive SRAM. Over-priced under-performing solutions, here we come.

Wouldn't it be easier to just stick to DRAM _without_ extra abstraction layers to start with? You know, instead of then having to pay a mint for SRAM just to get back to where you started?

Not meant as a flame. Just a quick reflection on how the real world is that-a-way, and utopias with a dozen abstraction layers are in the exact opposite direction.