Yet Another Consideration Courtesy of Rambus
Aug 08 '00
Well, with the ushering of the year 2000 and the passing of a new millennium, Intel and a company called Rambus introduced a new memory technology that they hope computer users will be implementing in the next ten years. I saw test computers that used this new memory technology, called Rambus inline memory modules (RIMMs for short), and I have to say that I have some misgivings about it.
Intel has been attempting to design system boards that work with RIMMs, but so far have not had much success. I have actually seen one computer model that used this technology get canned because of the bugs introduced by the architecture. The technical considerations were too great to delineate here, but suffice it to say, RIMMs aren't ready.
With DIMMs, the advice of my fellow epinionators, like shauncool (his review is probably one of the top articles on this subject), applies. There is no reason to pay someone else $50 to install your memory for you. It is very simple to align the memory module into the slot and pop it into place. But with RIMMs, you practically have to be a systems engineer to correctly install it. And that is not an understatement.
I am a technical writer for a major computer manufacturer in the southeast United States. I wrote the user manuals for three computers that used Intel system boards designed for RIMMs. The considerations were mind-boggling. The average user must beware. RIMMs and DIMMs are not compatible, nor can RIMMs be installed in DIMM slots. That is the most important thing to understand. I bring that up because RIMMs look like they ought to fit, and I want it to be clear that you can't walk into the computer store and pick up these "awesome" memory modules with the 300-400 MHz clock speeds and expect them to work in a computer designed for 100-133 MHz memory modules.
But, wait, it gets better. Let's say that you are sporting one of these computers designed for RIMMs. Here are all the considerations you have to consider, based on what I remember from the documentation that I had to produce (and consult lawyers and engineers about for six months in the process) --
1. All RIMM slots on your system board must be populated
RIMMs work in series, and their signal must be continuous. Even if you don't have a RIMM in a memory slot, you have to have something. So there is another card that you have to own for this purpose. It's called a continuity RIMM or c-RIMM. It looks a lot like a RIMM, but it has no memory on it. Its only purpose is to keep the connection across the RIMM slots going.
2. It's not advisable to mix and match RIMM speeds
Early incarnations of RIMMs caused instability in the operation of the computer when the RIMM speeds were mismatched. 300 MHz RIMMs did not work at all with 400 MHz RIMMs, and 356 MHz RIMMs didn't work with 300 MHz RIMMs if a 400 MHz RIMM was also in the computer. It got better, but not by much. I think that support for 300 MHz RIMMs were eventually dropped, but not without some going out to market. But now, your computer runs at the slowest RIMM speed when memory speeds are mismatched. If you catch yourself with a computer that uses RIMMs, your best bet is to make sure that the RIMM speeds are the same.
3. All memory must be the same amount
With DIMMs, you could have a 128 MB memory module, a 64 MB memory module, and even a 32 MB memory module, and all your memory would get along. When I wrote the user manuals for the computers I documented, I was instructed that you can't do that with RIMMs. All your RIMMs must be the same size, whether 32 MB, 64 MB, or 128 MB. The reason has to do with stability in the computer, once again. Apparently, the architecture that uses RIMMs is just basically unstable. If you're considering a computer that uses RIMMs, watch out.
4. You might have a complex diagram to follow for memory installation
Depending on the arrangement of your memory slots, you might have a complex memory diagram to read that tells you how to install your memory. Sometimes, this is more complex than installing memory really should be. You have been warned.
5. Some models don't support RIMMs in every slot
Sometimes, you just want to max out your computer for all it is worth by filling it to the gills with all the memory you can put in it. I documented two computers that fried the system board anytime you populated all the RIMM slots with RIMMs. Apparently, the voltage across the system was too much for the system.
Is it really worth it to purchase a system board for RIMMs because you think that you are getting three times higher speed than with a PC100 DIMM? Consider this: RIMMs cost about three to four times as much as a PC100 DIMM of the same size, and it increases system performance by maybe about 15% to 20%. Some engineers in the business have argued that RIMMs actually process information more slowly than DIMMs. How can this be, you ask --their clock speeds are three times faster? I am a writer, not a hardware engineer, but the basics of it boil down to the complex architecture required to support RIMMs. RIMMs are just plain expensive, and you don't get as much bang for the buck as you should be getting for a technology that is so costly.
Perhaps when the bugs are worked out of the architecture, RIMMs will be ready. But right now, all they are to the user is another consideration to be aware of. Don't confuse yourself when you are shopping for your upgrade, and don't buy a RIMM if your computer uses DIMMs. They're not the same. For now, if you are building a computer, pay close attention to the specifications and ensure that you're not purchasing a system board that uses RIMMs. You won't save any money that way, and you certainly won't get much performance for what you spend.
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Epinions.com ID:
mayhawk
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Member: Michael Moore
Location: Cary, NC
Reviews written: 61
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