Slashdot Mirror
Intel To Pull Plug on RAMBUS, Use SDRAM?
Ratteau writes " Cahner's Group Electronic News, is reporting they have come across documents that Intel "has pulled the plug on plans to use Rambus direct memory in the mainstream PC market". " Given the troubled past with Rambus, this wouldn't surprise me - but it's a big move for Intel.
I work closely with a DIMM engineer working with PC100 and PC133 memory systems. We've been watching all the lawsuits flying recently. Here's a few links about royalty and patent lawsuits:
e ws/OEG20000324S0022
u es/200004/rambus&page=1
6 1500.htm
7
Rambus asks ITC to bar Hitachi, Sega imports: (3/24/00) http://www.eet.com/story/industry/semiconductor_n
Will Rambus Go Bust?: (4/17/2000) http://www.32bitsonline.com/article.php3?file=iss
Toshiba Signs Patent License Agreement with Rambus
For SDRAM & DDR SDRAM Memory and Controllers: (6/16/00) http://www.rambus.com/general/press_releases/pr_0
Tech Report Analysis of Toshiba agreement: (6/16/00) http://www.tech-report.com/onearticle.x/881
RAMBUS using patent claims to lift RDRAM share: (6/25/00): http://www.ebnews.com/story/OEG20000623S0042
DRAM industry considers antitrust lawsuit vs. RAMBUS: (7/10/00) http://www.techweb.com/wire/story/TWB20000710S000
400 Mhz is a really big jump from the industry standard 100 - 133 Mhz. Minor impedance variations from board to board in production can cause significant phase and wave form changes in such fast signals.
To accurately transmit 400 Mhz square waves it is necessary for the board traces to handle 4 Ghz sine wave signals. That is more of an Analog micro wave transmission problem than it is any kind of digital design problem. Evidently the board designers have had a great deal of trouble doing this.
The bottom line is that Rambus motherboards will need to be produced with tighter tolerance on both trace and board substrate thickness than current motherboards. Result: even more expense for a Rambus system compared to a DDR based system.
Basically, RAMBUS has the theoretical capability to be significantly faster than SDRAM (not DDR, more later). However, the controllers have problems that prevent this. Basically, RDRAM can keep many pages open and many devices active at a time (more than SDRAM), but the i820 doesn't do this. So the chipset is crippling the RDRAM. Also, as soon as multiple devices are put on the bus, the latencies increase, so if too many chips are present things slow down. This is because of the longer wires needed. at 400MHz (not 800 - its DDR) that really matters. Also, RDRAM has been hindered by low yields and hence higher cost. It is now down to about double PC133 (see pricewatch). Also, the chips are more complex. However, the specs say that a good controller ought to be able to outperform PC133. Not by huge amounts, but by enough to matter. i820 is far from a good controller. Something to think about: the EV7 (maybe EV68, I can't remember) is going to use RDRAM. (also on Ace's hardware). However, it is going to increase performance by using 8 channels in parallel. So until there is a good desktop controller, and RDRAM is similar in price, AND the benchmarks say it's better, I'm using DDR SDRAM. But, the technology isn't inherently bad, just having more than it's share of problems.
---
It takes less power to run your CPU than a light bulb. On the desktop, power consumption doesn't matter so much as long as you can dissipate the heat. Transmeta already has a solution for reducing power use in mobile devices. Intel is doing the intelligent thing by occasionally devoting some time and R&D money toward developing lower power CPUs, but focusing on the biggest, best, and brightest.
In response to your core question, IE "who actually needs a processor this fast", the answer is, we all do. As higher-end CPUs get faster, lower-end CPUs get cheaper. As more processing power becomes available, we are able to predict weather more accurately, make more fuel efficient automobiles, and discover more about the cosmos in which we are only a tiny speck. Computers help us do everything, making products cheaper and giving a better way of life to all people (though admittedly there are billions for whom the benefits are slow to trickle down to.)
Next time you buy a car, stop a moment and marvel at the amount of processor time that went into modeling various aerodynamics characteristics, enabling you to get dramatically better gas mileage than the refinements made to the engine alone; Which are all designed and tested on the computer before they ever see metal. This is true of nearly every product with more than five moving parts, and many that have none at all. Be thankful for the race to technology, or get the hell off your computer and go plant some carrots or something.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
You hit the nail on the head, except...
RAMBUS gives almost as good performance as PC133, not DDR gives almost as good performance as RAMBUS, as you said.
Last year I had the priviledge of excersizing my masochism by working on an RDRAM mobo. While reading up on the architecture I said (aloud) "Gee, all this bandwidth is great and all, but the latency is so high won't that kill performance?" The Rambus Inc(tm) PowerPoint slides said no, bandwidth is all that matters, ignore the high latency. But the engineers I worked with were also skeptical. And it turns out we were right to be so, because RAMBUS sucks it up in real-world performance.
Other than that, though, you're right. And it is a sunovabitch to design for. When you have pico-seconds of margin to deal with at the _motherboard trace_ level, you know you're screwed.
The enemies of Democracy are
Intel's Desktop 2001 Roadmap Update indicates direct Rambus DRAM (RDRAM) will only be used in the high-end desk-top market
So it's not like Intel is giving up on RDRAM altogether - just on the lower-end machines. If they were switching because one is better, then they would just drop RDRAM totally.
Being with you, it's just one epiphany after another
The release of their 815i chipset already pointed in this direction (Rambus didn't really like that move :)
Also, the 815i chipset seems to be faster then the 820i chipset (which uses expensive Rambus memory). Now, it looks like they're indeed going to drop it. Look at some of these articles:
Every expression is true, for a given value of 'true'
It is silly to use Rambus RAM, since SDRAM has lower latency. Rambus RAM has higher bandwidth, but if you need bandwidth you can always interleave memory. (the idea is similar to RAID striping. byte 1 comes from one ram chip, byte 2 comes from the other, so you have the same latency and twice the bandwidth. If you want more bandwidth, use more controllers and more chips. You can't do anything about latency except make each chip faster, though, which is why there's nothing you can do with Rambus to make it have SDRAM latency.)
#define X(x,y) x##y
#define X(x,y) x##y
Peter Cordes ; e-mail: X(peter@cordes ,
Well this isn't a bad move on intels part since they really dont need their high end systems having a $800 price difference from AMDs. Certainly they've wasted a TONNE of money and time over rambus and i'm sure they wouldn't be loosing out to AMD now if they had better directed all that effort.
:) Without the burden on rambus this should give intel a fighthing chance against amd and bring prices down more :)
However as I see it the current big looser is toshiba who I think are one of the few DRAM manufacturers that agreed to pay rambus royalties on DIMMS, in order to continue their license to produce RIMMs.
For those of you that dont remember this, rambus turned round and claimed that they had also patented regular SDRAM as well as their funky rambus. They started putting pressure on companies who already licensed rimm technology to pay up for dimm tech also. Toshiba (i think) were one of the few that complied, scared of loosing lucrative rambus contracts.
Now they are stuck paying royalties to rambus for dimms... and without the big return on rimms they could seriously dent their business.
AMD on the other hand got it right and i'm well pleased