First introduced to the desktop PC market over a year ago, Synchronous Dynamic Random Access Memory (SDRAM for short) has since then become a hideous fad most PC users have caught on to, however is SDRAM really necessary?  To answer that question you must first look at the migration from good old 72pin SIMMs to the 168pin monsters you see today called DIMMs.  It all started in a place you wouldn’t normally consider, inside Apple Computer's own Power Macintosh. What exactly was inside these Power MACs?

Limitation #1

Support for up to and in excess of 1GB of RAM. Apple knew that the type of users that would absolutely need a MAC would be professionals interested in DV editing as well as desktop publishing...in turn, they needed RAM. In order to fulfill the demanding needs of the user, Apple took a huge step forward from the normal means of memory expansion, which both PC and MAC owners had been using for years: 72pin SIMM (Single Inline Memory Modules). At the time, the 486 was still popular among average users, Cyrix had just introduced their 150MHz PR-200+ processor and the 32MB EDO SIMM finally made its way into the mainstream market. Realizing that installing a total of 1GB of RAM with 32MB SIMMs would put heavy limitations on various aspects of the motherboard's design (physical layout, chipset, etc...), Apple therefore decided to make an almost instantaneous migration to the newly announced RAM specification standard, the Dual In-line Memory Module, commonly known as the DIMM. Mind you, we are still not talking about SDRAM, just plain old EDO DIMMs here. But why on earth would we invent another way of packaging RAM with no advantages over the technology that was current at the time? We wouldn't...that's why Apple implemented a technology with its fair set of advantages over standard SIMMs. Using the technology available at the time, one could easily fit 128MB on a single module, therefore increasing the realistic possibility of surpassing the 128MB and 512MB limits of everyday desktop PCs. Apple began outfitting their Power Macs with up to 12 of these DIMM slots, featuring 168 pins (84 pins on each side) and measuring approximately 5.25" in length. Apple managed to eliminate one major problem a 1GB memory capacity posed, physically fitting memory slots on the motherboard. However, one more major limitation remained, the chipset.

Limitation #2

Ever wonder why you only see a maximum of 3 DIMM and 4 SIMM slots on a TX based motherboard? And have you ever wondered why you cannot occupy all 7 slots at once? The answer to this question lies in between the "lines." A major function of the chipset on a motherboard is to map out the expandability features of that particular board, part of this duty deals with the number of RAS (Row Access Strobe) lines the chipset provides for. The TX chipset, for example, has 6 allocable RAS lines, with each Double RAS SDRAM DIMM occupying 2 RAS lines, a maximum of 3 DIMMs can be installed at once without exceeding this limit. Likewise, if Apple chose to stick with the 72 pin SIMM standard that would provide them with one major problem allocating the required number of RAS lines from the chipset to correspond for the number of SIMMs installed. Imagine this, a double RAS 32MB EDO DIMM occupies 2 RAS lines, and you would need at least 32 modules...an AMAZING amount! However, with 168 pin DIMMs you can simply use a few 128MB sticks and your problems are solved.

Eventually this trend caught on to the PC market, making its debut with Intel's 430VX Chipset, Although at most you would find 2 DIMM slots on any given VX board with a single DIMM slot being the norm. The PC industry decided to take DIMMs to a completely new level, instead of simply using the old asynchronous Extended Data Output standard (EDO) which boasted widespread use and an affordable price the industry chose to introduce a new type of DRAM. This new type of DRAM flaunted two major features: the ability to run at higher bus speeds more reliably, and support for synchronous data transfers. Here's when SDRAM finally made its introduction.

The BUS must not accelerate above 66MHz...

We all remember the huge jump from the 33MHz memory clock of the 486 to the 66MHz memory bus speed of the Pentium class systems. Well Intel wanted to keep the limit of the memory bus speed on our computers at 66MHz, and since the market seems to follow Intel blindly when it comes to things like this the memory industry spec’d EDO DRAM at a maximum operating bus frequency of 66MHz, and no more. However, it quickly became apparent that EDO RAM could be easily operated at bus speeds above 66MHz, although when reaching the 83.3MHz point stability becomes a tricky thing to achieve. Therefore when implementing SDRAM the bus speed specification was raised to the 100MHz-bus speed barrier, Intel’s next major jump. At the time this was only a plan Intel had decided on for their next generation processors. Since then we have finally started achieving bus speeds around the 100MHz mark in spite of the fact that Intel still hasn’t released a processor designed for any bus speed greater than 66MHz. Is SDRAM a requirement for bus speeds above 66MHz? Absolutely not! As long as you have some quality EDO SIMMs they will not have any problems at bus speeds up to 83.3MHz, their stability at the 100MHz-bus speed is still questionable though. It is highly unlikely that any 100MHz-bus speed motherboards (which will most likely be based on the ALi Aladdin V or the VIA MVP3) will support EDO RAM anyway, so that limitation isn’t something you should be concerned with.

When people go out to purchase SDRAM, their justification for doing so is that "they want to be able to use their SDRAM at the 100MHz-bus speed," what they aren’t aware of is the fact that until now we haven’t had any 100MHz-bus speeds to actually test those claims on. Sure a manufacturer can say that their SDRAM is rated at 100MHz, and should therefore theoretically work on any 100MHz-bus speed motherboards. The keyword there is THEORETICALLY; many ideas work in theory, however in practice they fail miserably. There is no guarantee that the SDRAM you buy today will work with the 100MHz-bus speed and there is absolutely no guarantee that the SDRAM you buy today will even work in upcoming motherboards.

So what’s the real deal?

The question you all looking for the answer to is: "Will my SDRAM work with upcoming BX motherboards?" The answer to that question? Well, since there are no guarantees in life (especially not in the computer world) there can’t be one straight answer, what will most likely happen is that SDRAM you buy today will be compatible with the upcoming BX based motherboards. Compatible doesn’t mean functional, the SDRAM you can buy today will theoretically (don’t you just love that word) work with a BX motherboard, whether or not it can stand up at the 100MHz bus speed is another question. Chances are that only the best quality SDRAM will survive with a BX motherboard and the 100MHz (+) bus speed. the tests that were run on ABIT’s LX6 - a 100MHz bus speed enabled Pentium II LX motherboard - indicate the following hypothesis: SDRAM in general will work at the 100MHz bus speed, however some modules have a tendency to work at the higher bus speeds than others.

ECC & EPROM…necessary or just a marketing trick?

Following Intel’s release of the LX chipset (everything seems to follow Intel’s release of a product) manufacturers began producing two new types of SDRAM: ECC SDRAM and SDRAM with onboard EPROM. Are these two types of SDRAM worth the extra $$$ it costs to purchase a module enabled with either or both of these features? This really depends on the type of user you are and the job the system will be performing. Error Correcting Code SDRAM (ECC SDRAM) is often necessary for server environments in which even the smallest error cannot be tolerated, however for normal desktop systems, gamers, or even professionals working in their home-office ECC SDRAM is NOT NECESSARY.

Then we move onto SDRAM with onboard EPROM…why on earth would you need EPROM on a SDRAM module? The technical answer to this question is that, onboard EPROM allows the modules to communicate with the chipset and in theory that enables the SDRAM to operate with more functionality and greater stability. The marketing answer to that question is simply that SDRAM with onboard EPROM is "better." What is the real world answer to that question? Here is an example of stability of SDRAM with onboard EPROM when compared to stability of SDRAM without onboard EPROM. Corsair Microsystems manufactures high quality SDRAM, however often times their modules are very difficult to obtain in Taiwan, where most of the motherboard research and development takes place and therefore manufacturers take for granted that their motherboards will function with Corsair’s high quality modules. Making assumptions such as that mentioned above can be deadly to your reputation. ABIT’s LX6, when operating at the 100MHz bus speed setting experienced random crashes and overall system instability when using 64MB of Corsair SDRAM (without EPROM). In order to eliminate some of this instability one must enter the BIOS Setup utility and take the SDRAM Latency Timing down to 3 (from 2) and disable SDRAM Speculative Read. However when using 64MB of Corsair SDRAM (with onboard EPROM) the user can easily run at the 100MHz bus setting with the BIOS timings set to their maximum level (SDRAM Latency Timing = 2; SDRAM Speculative Read = Enabled). Does this mean that SDRAM with onboard EPROM is worth the extra $30 - $90 per module? Decide on your own by considering the following example. Advanced Megatrends SDRAM, one of the most overall compatible types of SDRAM does not feature onboard EPROM and was designed months before the LX chipset ever went into mass production. Yet when using it on ABIT’s LX6 you can easily achieve rock solid stability (equivalent to that achieved when using Corsair SDRAM w/ onboard EPROM) at the 100MHz bus speed setting using the most aggressive BIOS timings.

Keep yourself in check…

So how do I know what type of SDRAM to buy? You may have heard people talk about certain types of SDRAM "chips" being better than others, they are usually referring to the physical chips on the SDRAM DIMM. And although they are technically correct in assuming that two identically manufactured memory chips from the same manufacturer will be equivalently reliable there is one thing they are not considering…something that can be summed up in 3 simple letters, P C B.

PCB, an engineering acronym standing for Printed Circuit Board is the physical board on which a circuit is printed (or etched) on. Even though you may have two SDRAM DIMMs both using NEC chips the PCB’s used with each module are completely different and could possibly determine whether or not the modules will work at higher bus speeds reliably, or even in pairs on some motherboards.

Quality in SDRAM doesn’t stem entirely from the chips used on the modules, although they do play a major role in the long-term stability/reliability of the module. Think of it this way, if you have a bridge with a roadbed that can hold 20 tons of weight what does it matter if the towers supporting the roadbed can only hold 5 tons? The same principle applies to SDRAM, if you have high quality NEC or SEC (Samsung Semiconductor) chips on a DRAM module what good will they do if you have a poorly manufactured PCB? The general rule of thumb when buying SDRAM is this, be sure to get genuine manufacturer produced modules, so if someone claims to be selling "Samsung SDRAM" be sure the entire SDRAM module was manufactured by Samsung not just the chips. With SDRAM, never settle for generic, if you find yourself in a tight money situation either wait or buy EDO because in the long run generic SDRAM will do more harm than good.

Ok…ok…I understand…but what brand of SDRAM should I buy?

Advanced Megatrends

The Advanced Megatrends SDRAM has had the greatest success rate I have personally confirmed with the motherboards tested on this site. Out of all of the motherboards reviewed there were only about 5 that weren’t completely stable when using the Advanced Megatrends SDRAM (2 of which weren’t stable with other modules as well). The reason for the immense success of the Advanced Megatrends SDRAM is the manufacturing process the modules are produced by. Their newer SDRAM modules are produced using an 8 layer PCB (rule of thumb: more layers, the better) and use NEC or Toshiba chips. The price on the Advanced Megatrends SDRAM is very competitive (around $119 for 32MB) although you can still find some generic modules for much cheaper. The only problem with the Advanced Megatrends SDRAM is that you can only order it from one place, Megatrends Technologies, I have never had any problems with them personally however there have been a few cases where customers received service they weren’t too happy about. It all depends on how much you want high quality SDRAM I guess.

Corsair

Corsair’s SDRAM used to be among the best, and for some time it was, however the inability of quite a few motherboard manufacturers to perform sufficient testing on Corsair modules caused them to slowly lose their place at the top of the hill. Fortunately Corsair seems to be making a comeback with their newer SDRAM modules, their 64MB SDRAM DIMM w/ onboard EPROM rivals some of the best out today. However the price on Corsair’s SDRAM is still out of the each of many

Fujitsu

Fujitsu SDRAM has been often referred to as the entry level SDRAM module, however I have yet to personally test any so I cannot comment much on their manufacturing process. I will post more information once I can get my hands on a few sticks of their SDRAM.

Samsung

We have all heard the wonderful praises for Samsung SDRAM, however most of you have probably wondered if the unbelievable claims about their SDRAM are dumbfounded or actually substantiated. Let me just say this now, they are definitely substantiated! What makes Samsung SDRAM better than most of the competition? It’s basically this: motherboard manufacturers have very easy access to Samsung SDRAM, and lots of it, so naturally they are able to test their motherboards with readily available modules more efficiently than modules they have to search long and hard for. The stability of Samsung SDRAM is on par with that of Advanced Megatrends SDRAM if not greater, be aware of imitation modules that simply use Samsung chips. The Samsung manufacturing process is second to none, a truly excellent innovation. I have only personally used Samsung SDRAM once in my lifetime and I was truly amazed, I will try to get my hands on some more modules for testing so I can further extend this comparison of SDRAM brands.

SmarTech

SmarTech SDRAM has found its popularity among MTech motherboard users simply because it is the absolute best SDRAM to use with the most picky of MTech’s motherboards, the Mustang. Using NEC chips and a 6 layer PCB SmarTech SDRAM will work in nearly any configuration you throw at it, although it still takes a back seat to the newer Corsair modules as well as the Advanced Megatrends and Samsung sticks. When using SmarTech SDRAM however you may have to be a bit more generous with your memory timings in the BIOS Setup utility, however for the most part anything a Megatrends module can do a SmarTech module can do. Finding SmarTech SDRAM is another discussion though…lately it has become quite a rarity, good luck finding some =)

SDRAM vs EDO - Benchmarks

If you are still not convinced of the minimal performance increase SDRAM offers over EDO, here are a few benchmarks to back up the earlier claims.  The test system was an AMD K6-233 on an ASUS TXP4-X (TX based) Socket-7 motherboard, the only variable that was altered during the tests was the RAM configuration.  The BIOS timings were set at the lowest possible setting to ensure that the Business Winstone tests would complete successfully, 2 x 32MB sticks of Corsair SDRAM were used in the SDRAM tests and were then swapped out for 2 x 32MB Micron EDO SIMMs for the EDO tests. 

At the 66MHz bus speed, there is hardly any difference in performance when using SDRAM vs when using EDO (about 1% increase with SDRAM) even when using the 83MHz bus speed the performance increase is minimal.  Right now the only reason to go with SDRAM (unless you take into account future use of your RAM modules) is the increased stability at higher bus speeds, that's all. 

Conclusion

So what is the final verdict…is SDRAM all hype or the future of the memory industry? Right now, there is absolutely no logical reason to opt to purchase SDRAM over EDO if you’re on a tight budget. If you can afford it however, you are better off buying some high quality modules and using them with much more ease than EDO SIMMs. Gold is just as shiny as Aluminum Foil…does that mean that Aluminum Foil is just as good as gold? SDRAM can be very similar in appearance but very different in reality, remember that in theoretical applications all SDRAM is created equal…however by saying that I couldn’t be further from the truth.