What's the deal with RDRAM?

[Brian]

I got a p4 motherboard on eBay for $11.99. Catch was it was socket 423. My friend gave me a p4 1.3. I'm almost there. Now, why is RDRAM so expensive relative to DDR? It seems they still manufacture it. Looks like I'm in for $120+ for 512 used. How does it compare to DDR?

[egslim]

In short, the company that designed RDRAM did their best to piss off most of the industry.

RDRAM is still produced for and used in some high end servers, embedded devices and the PS2, but it has been pretty much expelled from the general pc market.

[Hellbound]

RDRAM and DDR RAM are similar in overall performance, but achieve it differently.

RDRAM has bus speeds of about 800MHz. This sounds awesome compared to the 266 and 333 of DDR RAM. However, RDRAM uses a smaller word size. It only runs 8 bits for every clock cycle, giving you (800MHz*8bits) 6.4Gbps. It has (IIRC) a thoretical limit of 1200MHz, giving a maximum throughput of 9.6Gbps.

DDR RAM runs at 266 or 333, but handles 32-bit words. That gives speeds of 8.5Gbps and 10.6Gbps. DDR has a theoretical limit of 400MHz, giving a maximum throughput of 12.8Gbps.

[ImpyTimpy]

Actually, DDR RAM can go higher then 400... :eek:

Originally posted by Huntsman
RDRAM and DDR RAM are similar in overall performance, but achieve it differently.

RDRAM has bus speeds of about 800MHz. This sounds awesome compared to the 266 and 333 of DDR RAM. However, RDRAM uses a smaller word size. It only runs 8 bits for every clock cycle, giving you (800MHz*8bits) 6.4Gbps. It has (IIRC) a thoretical limit of 1200MHz, giving a maximum throughput of 9.6Gbps.

DDR RAM runs at 266 or 333, but handles 32-bit words. That gives speeds of 8.5Gbps and 10.6Gbps. DDR has a theoretical limit of 400MHz, giving a maximum throughput of 12.8Gbps.

[a_unique_person]

The problem with RDRAM is that there is nothing wrong with it from a technical point of view, just that the politics, backstabbing and double dealing were of such a ridiculous extreme that in the end, no one wanted anything to do with the company that owns the patent for it.

Rambus Inc invented and patented the concept of RDRAM. Fair enough. They were also the poster boys of a new business model. They would make all their money from their intellectual property, and make nothing. All their income would come from licences they handed out to other companies to make the actual objects that were sold, in this case, RDRAM.

The hi-tech industry has, for many years, had much of a co-op feel to it. This was because in the early days, when processes were much newer, it was always good to have a 'second source' for your products. It meant that anyone committing themselves to your product knew that, even if your company went under, or your manufacturing process went pear shaped for some unknown reason, they could always buy it from the backup source.

Also, the need for standards became apparent pretty early on, and so there are numerous get togethers of companies to make sure everyone is singing from the same hymm book.

Rambus did two things. It got Intel to sign an exclusive deal for a number of years that meant that Intel could only design chipsets and motherboards that used RDRAM. IIRC, this meant that Intel would have exclusive rights to RDRAM, that is, AMD, it's competitor, couldn't use this newer and faster technology. It would be stuck with the slower SDRAM.

It also went along to the Industry standards committee, where they were dreaming up the standard for the next generation of SDRAM, DDRAM. Rambus was nice enough to give some handy hints as to how they could make the DDRAM work better.

So Rambus was doing pretty well, it had a monopoly on Intel using only it's RAM, which was the worlds number one CPU maker for PCs. It charged what it liked, and didn't have to worry about the tedious manufacturing, distribution or marketing of actual products. It just had to watch the money roll in.

Then it decided to sue the DDRAM people breaching it's patents. The handy hints it had dropped at the standards meeting were for technology it had already taken out patents on, only it hadn't let anyone know this at the time. Not only was it going to make money on RDRAM, but SDRAM as well.

At this point everyone had had enough. Rambus was a marked corporation. Intel was stuck with trying to flog chips that only worked with a product that was very expensive. The hoards were flocking to SDRAM instead, even if it wasn't as fast, because it was cheaper and it worked. This meant that Intel chipsets weren't being used in computers, but it's comepetitors chipsets, from VIA and ACER Labs.

AMD was doing very nicely too. Intel was hobbled with a contract that was costing it a fortune, and Rambus was trying to take on the semiconductor world.

Rambus took on too much, and it lost. Hubris and greed. Good riddance to them.

That is why your motherboard is so cheap. Rambus is dead. The RDRAM still costs a fortune.

[Brian]

Thank you.

[a_unique_person]

I hope you read it all. I'll be asking a few questions to make sure you did.

[Prospero]

Is it weird that I was entertained by that even though I have no real use for that knowledge?

[egslim]

Rambus did two things. It got Intel to sign an exclusive deal for a number of years that meant that Intel could only design chipsets and motherboards that used RDRAM. IIRC, this meant that Intel would have exclusive rights to RDRAM, that is, AMD, it's competitor, couldn't use this newer and faster technology. It would be stuck with the slower SDRAM.
Actually, AMD does have a license to use RDRAM. Needless to say, they have never used it and never will.

While RMBS and Intel tried to push the market to RDRAM, AMD and VIA offered DDR-SDRAM as an alternative. The market chose them. After that, fierce competition in the DDR market made the technology accelerate faster than RDRAM. Competition is great...:cool:

[a_unique_person]

I stand corrected. It is such a complicated story that I expected I would get something wrong in there somewhere. The market has worked in this case, but Rambus had a good try at screwing it.

[Hellbound]

Originally posted by ImpyTimpy
Actually, DDR RAM can go higher then 400... :eek:



Eh, cut me a break. Since April I've spent all my time in a country where a mechanical pencil is a technological wonder of the age.

I have not seen a flushing toilet in over 6 freaking months!!!!!!!!!!!
Not that I'm bitter...

[ Huntsman returns to cleaning his M-16, muttering imperceptibly... ]

[ImpyTimpy]

Don't worry, I thought I was buying the latest and greatest when I bought a board with FSB at 800 MHZ except now I find they're making them go up to 1000MHZ.. And PC3200 is old news... :( I've seen PC3500/PC3700 chips a lot. (DDR433/466!)

Originally posted by Huntsman


Eh, cut me a break. Since April I've spent all my time in a country where a mechanical pencil is a technological wonder of the age.

I have not seen a flushing toilet in over 6 freaking months!!!!!!!!!!!
Not that I'm bitter...

[ Huntsman returns to cleaning his M-16, muttering imperceptibly... ]

[egslim]

Unfortunately, anything above PC3200 is not an officially supported JEDEC standard. Also, these "PC4000" modules often have poor timings.

[a_unique_person]

I have been seeing PCs with poor timings for the past 10 years. That is the only thing that really scares me with these newer bus speeds, the fact that they are getting up to the limits of the ability of the average mother board designer and builder to do a decent job. 400MHZ? You aren't far from microwave.

[Hellbound]

Originally posted by a_unique_person
I have been seeing PCs with poor timings for the past 10 years. That is the only thing that really scares me with these newer bus speeds, the fact that they are getting up to the limits of the ability of the average mother board designer and builder to do a decent job. 400MHZ? You aren't far from microwave.

Cool, does that mean your computer can make popcorn while you web surf? :wink8: