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Create Your Own Psuedo-RDRAM
ucsimon writes: "For those of you who like to overclock, this is truly some hardcore stuff that shows how to convert SDRAM to RDRam. I value my ram too much to try, but I wonder if anyone out there has tried this yet. " Having the same sentimental attachment to my RAM that most people do, I haven't even attempted this either - anyone know if this works, even in theory? Post below. [Updated 28th April by timothy:] Well, this won't actually convert your SDRAM to RDRAM of course, but it will add to your heat-slurping overclocking abilities.
This article has NOTHING to do with turning SDRAM into RDRAM.. All they did was put a copper shield on a stick of SDRAM, making it look similar to a real RDRAM module.
Doesn't Slashdot occasionally GLANCE at the links that are submitted before posting them?
The author comments that 150 MHz is a "trouble region" because there's "more" EMI at that frequency. Bullshit. EMI just has to be present to be a problem, not at a particular frequency. 150MHz is only a problem because the RAM is designed for 133MHz.
Can't have one without the other. That is to say a changing electric field produces a changing magnetic field and vice versa. A faraday cage stops electric fields so it stops high frequency magnetic fields. (The fields will pass through on the order of a few wavelengths, so having the shield so close to the chip is not going to do much for you.)
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I don't think so. The article goes on to talk about overclocking the bus to take advantage of the EMI shield, but the person who did the conversion didn't have fast enough hardware to allow it. But the obvious point was to make the RAM faster than SDRAM is sposed to go, which would mean making it ACT (not be == to) like RDRAM.
"Spread Spectrum Clocking (SSC) is a frequency modulation technique for EMI reduction. In the latest motherboards, the master clock generator chip does not maintain a constant frequency."
As far as I know, what SSC does is jiggle the clock frequency a little, thus spreading EMI emissions out across a slightly wider range of frequencies. In other words, it gets around FCC EMI regulations without actually reducing the amount of energy radiated.
The metal plate in Rambus isn't just an EMF shield--it also functions as a heat sink, as not only do RDRAM modules run hot, the heat production is concentrated in a very small area. I'm guessing that any speed increase the mad overclockers saw in their SDRAM was due more to improved heat dissipation than anything else.
"I'm not just an elder god, I'm cute too!"
See Rambus's RIMM design guide, section 8.2.1 "Mechanical Components - Heatspreader/Cover Reference Design". More info can be found on Intel's developer site, on the RIMM Module Reference Design page, under the section "Production Heat Spreader Reference Design".
Basically, RDRAM RIMMs give off a lot of heat, plus the heat is produced in a very small area. The aluminum covers are necessary to prevent hot spots. If you look at the figure 8-1 "Double-Sided RIMM Module Assembly-Exploded View", you'll see that the reference design calls for a thermal pad (Or thermal grease) between the heat spreader and the RDRAM chips.
Anyway, I went to google for some links.
Here is a fairly general overview of EMI in computers. It talks about various strategies for dealing with it.
Here is an article mostly about SDRAM, but which says the following: "Spread Spectrum Clocking (SSC) is a frequency modulation technique for EMI reduction. In the latest motherboards, the master clock generator chip does not maintain a constant frequency." Anyone know if that is true? I didn't know that...
Finally, an article showing Intel is concerned about the problems of EMI in modern computers.
All in all, interesting stuff (I love absurb overclocking articles!) but I would like to have found some evidence that shielding memory like they did has any real benefit.
This comes in really handy as I just converted my 16MHz i386 to 1.5GHz Willamette, which as we all know doesn't support SDRAM for now. Now if could just convert that 5.25" floppy drive to a DVD-RAM drive...
The article doesn't go into converting SDRAM into RDRAM at all. It's about making an EMI shielding for your SDRAM chips. This doesn't make the SDRAM into RDRAM although it make look like it. It's sort of like taking a saturn and putting a porsche body on top of it and expecting it to perform like a porsche.
RDRAM uses a 8 or 16 bit channel running at 300 to 400+ MHz with data being sent on the rising and falling edges of the clock. SDRAM runs at 100MHz on a 32bit bus that sends data on the rising edge only. Turning SDRAM into RDRAM would involve replacing the memory interface and control circuits on the SDRAM and changing the packing to fit in a RIMM. If you can do this, you'll probably do better to work as a chip designer for a semiconductor company and using the money you earn to buy some RDRAM.
"When you sit with a nice girl for two hours, it seems like two minutes. When you sit on a hot stove for two minutes, it
I know a few of these points have been brought up already, but let me summarize and add my own thoughts:
:)
1) The metal bracket on RIMMS isn't for EMI shielding, it's for heat. It's just like the heatsink on your CPU, which doesn't add to the EMI protection noticably.
2) A 150MHz SDRAM dimm isn't RDRAM. Rambus uses an entirely different protocol, and anyway... 150Mhz SDRAM is probably faster than rambus.
3) Your SDRAM won't work at 150MHz because it's simply too fast for the junctions to switch, not because of EMI. If you've got a serious EMI problem, you'll probably see it if you're overclocking or not.
4) That design shown probably wouldn't fix an EMI problem, either. It'll most likely act as an antenna, worsening the problem.
BUT... To whoever made that page.. Keep hacking. While this idea might not have worked, you may come up with a great supercooled DIMM refrigerator or something. Good luck.
Likewise, the Soyo SY-6VBA 133 allows it, as well. Up to 155, actually. It also allows you to run your RAM slower than the rest of the system bus. As in, I've got a PIII 450 running at 600 on the 133fsb, but my ram is only at 100. So if I had a nasty-ass coppermine, I'd be able to punch it up to 155 and keep my ram at a gentle ~116.5Mhz The AGP and PCI are another story, tho. Dirk
I keep trying to pick fights, but I can't shake this Excellent karma.
I'm only into overclocking if it makes my system FASTER...
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E2 IN2 IE?
Sorry for being off-topic, but I'm just wondering..?
70 is fast for you? 70 x 1.6 = 112 km/h. That is 2 km/h more than the legal speed limit on freeways here in Denmark. This is considered slow. Most people driving on the freeway is doing 130-140 km/h (~85-90 mph).
Just wondering..
Remember, there are no stupid questions. But there are a lot of inquisitive idiots.
Intersting hack. But I wonder if it's worth all the effort and sliced, bloddy fingers. It just seems you're putting too much effort in something that you won't get much back from.
Also there is one quesiton: stability? What happens when the homebrewed shield falls off?
RAMBUS prices will go down. For the rest of us, we will wait for that event.
If design is not Bauhaus, it is Baroque.
I think that attempting this would almost always be doomed to fail, since I don't think any reasonable motherboard would allow such a high FSB, and if it did, you'd get a shitload of trouble from stuff like the PCI bus being linked to the FSB and PCI devices not liking a higher clock...
The illegal we do immediately. The unconstitutional takes a little longer.
--Henry Kissinger
Here is the working link...
The illegal we do immediately. The unconstitutional takes a little longer.
--Henry Kissinger
This article merely tells you to make an SDRAM module look like and RDRAM by giving it a shield agains electromagnetic emissions. This might have some benefit in very rare cases, but realistically, it's totally pointless.
The illegal we do immediately. The unconstitutional takes a little longer.
--Henry Kissinger
A metal shield over the chip will NOT reduce magnetic or radiation effects. The shield will simply SCATTER magnetic interference, NOT block it. RDRAM chips are engineered to protect against interference which encompases much more than tin foil. Personally, I prefer paying for RDRAM chips that actually do protect against interference rather than hacking a cheap DIMM chip and randomly scatter magnetic anomolies throughout my system RAM.
It's clear to me (a seasoned electrical engineer with 15 years of RF/EMC experience) that this author has too much time on his hands and is now about to waste the reader's time too. If the concern is EMI getting into the RAM chip (and slowing it down or screwing it up), then yes, a bit of a shield might do something (however minor). But, don't forget that these shields work both ways! If the traces on the boards and/or the IC leadframes themselves are radiating due to changing logic states (quickly!), then how do you think they will react to having that signal travel the short distance to the shield, and then being reflected back to the source? Adding signals together with a short time delay (travel time to the shield and back) is always messy and sometimes creates signal cancelation--which is not good!. Given the distance between the sources and the receptors, I'd say this chap is chasing the wrong idea. If he's worried about signals getting into his RAM and slowing it down, then better to have a good metal case on his unit and--if he's really concerned about signal reflections--perhaps adding a little carbon based RF absorber lining the inside of the case. I for one, don't want to start reflecting signals from my computer parts directly back into them by putting close spaced shields around the individual parts. The RAM boards were not designed with this in mind and most certainly have not been tested to operate in this fashion. So play all you want with your individual computer system, but please educate yourself before advising others that "This is a good thing. Try it." From my perspective, you're doing more damage than good to this community.
They sell special *thin* flexible tape used in RF shielded screen rooms. Basiclly like copper-foil tape. Wouldn't it just be easier to tape your RAM with that stuff and use an ag-clip for the gnd? The tape is available as non-conductive on the back(sticky) side.
See, RDRAM has large latency (approx. 28 cycles @ 400MHz for a random access = 70ns) but for sequential accesses it spews the data out very very fast indeed (a 16-bit-channel RDRAM setup at 400MHz can spew out 16 bytes in 4 cycles = 10ns; a 32-bit-channel dual-chip setup - only found in consoles - can double this to 32 bytes in 10ns).
This is great for consoles, where you have lots of DMA going concurrently with semi-random CPU cacheline refills. For this application, RDRAM is much, much cheaper than the alternative (which would be 128-bit-wide, 100MHz synchronous RAM of some flavor). RDRAM also wins hands down on simplicity of system design since its data bus is only 16 bits, or 32 bits in dual-chip setups, plus only 8 more bits for addressing. It provides superb theoretical bandwidth, which can be approached quite closely in a well-designed console (er ... can someone build a well-designed console for me? ;)
However, for PCs, the case is much less clear cut. DMA seems to be far less important these days, and you certainly won't see half a dozen concurrent DMA channels going over a 200MHz FSB anytime soon. Even building a 200MHz FSB would be practically impossible in a modular system such as the desktop PC. Consoles are so non-modular, the current crop are internally dense as hell with heatsinks and EMI shielding, and the primary internal busses are no more than half an inch long.
To make RDRAM work great with a desktop PC would take, in my estimation, far, far better RDRAM controllers than are currently available, and integrated much more tightly with the CPU, and communicating over a synchronous bus of at least 128 bits.
RDRAM definitely wins on bandwidth, but its latency is so atrocious that you need a good prediction of what data is needed next ... easy to do on a dozen DMA channels but when the primary channel is the CPU it's near-impossible.
In summary, RDRAM is too application-specific to be suitable for desktop PCs, and the controllers are not yet mature enough to get anything like full speed from it in Real World PC applications.
Not to mention the fact that it's proprietary, so it intrinsically costs more to manufacture than other RAM designs.
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-- Danny Vermin
This reminds me of high end audio freaks who paint the outsides of their CDs to prevent environmental light disturbing the laser, or fill their Amps with acrylic so the electrons in the circuits wont be affected by vibrations.
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Let's hear it for moderation folks! (And for those of you who have itching fingers to mark this down as a troll or something, give it up. It's a serious post. Don't waste your points, find something actually worth reading somewhere and bring it to the top. If I was trolling I would not be using my name, as thats just stupid.)
I am a leaf on the wind. Watch how I soar.
It looks like it would be a fairly straightforward project. If you have the skill to bend up a bit of copper and make sure it doesn't touch anything important, that's all there is to it. Basically the whole point of the project is to just shield the chip from EMI. You don't modify the chip or anything, just form a piece of copper and slip it over. If I were into OC'ing or owned a clear case (no shielding) I would jump right on this project.
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An armed society is a polite society
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Check out this test sharky did, were talking VERY minor speed increases. in the actuall apps(err, games :o) :o)
Check out the mem. specific stuff here, not to worry. This link works
Why does my links act(i would have said something else, but i hurts my karma!!) up? the html is correct, THANK YOU.. and the complete mb review, here
Its interesting stuff, i know it saved me from running out getting a i820 based motherboard.
"Theres alotta savages in this town.."
That page was about reducing EMI in your ram in case you are overclocking your system, not converting SDRAM to RAMBUS. They just mention in the beginning why RAMBUS has the shielding.
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