What is the deal with the different types of RAM?

I go to Pricewatch.com and there are many different types of RAM listed.

Ok, I know that PC100 is what my computer has now, and that RDRAM is for Pentium 4 boards, and that EDO is for my old Pentium1, but what is the deal with the PC3200 to PC1600? On what MB’s can it be used? What are the advantages to them?

They are all various types of (DDR)-SDRAMS. You can use a board with a higher rating in a slot with a lower rating, you just won’t get the benefit of speed.

The PC3200 and PC1600 etc etc are types of DDR (Double Data Rate) RAM. There are a lot of motherboards out there that support this type of RAM (Intel and AMD… although I would check out Tom’s Hardware to see how both processors work with DDR RAM).


What exactly do the different numbers mean?

Speed. If I can remember correctly its MB/s transfer rate.
Please not that you need a motherboard that specifically supports DDR ram to use it, and that the bus speed it runs at will ultimately determine the RAM’s speed - the numbers are just what the RAM is able to perform.

now to get into what makes DDR different to SD and RD, what FP and edo ram were, and what ECC and registered RAM is (answer : they are slow DDR is fast)

DDR Ram transfers data on both side of the clock-cycle, effectively doubling performance. The various numbers refer essentially to the speed.

The type of core logic chipset that is incorporated in the mobo dicates the type of RAM that can be used. PC2100 DDR Ram, which operates at 133 Mgz X 2 = 266 Mgz is the DDR de facto standard right now. Recently, VIA released a chipset which supports 333 Mz DDR, which is a bit faster.

Memory speed is important on higher-end machines as older, slower memory can’t feed data to the processor fast enough, effectively bottlenecking the system and slowing it down. Rambus memory is theoretically the fastest, but it’s high cost led Intel to abandon their Rambus-only architectures. In the real world, DDR seems to offer comparable performance at a lower price.

You’ll see many of the large vendors offering steeply discounted Pentium systems based on PC133 chipsets as they try to clear their older inventory. While they often have fast processors, overall performance drags a bit when compared to a similar system with DDR or Rambus. Depending on the price-cut, you may or may not want to invest in one.

The clock-speed wars between Intel and AMD have effectively brought us processors that in most cases greatly exceed the needs of most users (exceptions - graphics artists, gamers, etc). One more reason why I buy AMD - Intel needs the competition to keep them honest. Anyone remember the first Pentiums?:

60, 66, 75, 90, 100, 120, 133, 150, 166, 200 mz, each at a significant price premium over the previous release for only minor performance gains. Throw in viable competition, and we now have 2+ Gz processors with relatively short life-cycles between iterations.

BTW, IMHO now is a good time to buy a machine - prices are low due to short demand, and performance won’t scale up too quickly until AMD catches up in clock frequency fight (even though their chips generally perform as well as Pentiums rated at much higher speeds).

I have some time so I’ll go through some history.

EDO (Extended Data Output) RAM (Random Access Memory) I believe was the first widely available RAM (if not the first). I was basically phased out around the advent of the Pentium II processor when computers switched to SDRAM (Synchronous Dynamic RAM). Basically SDRAM synchronizes with your computers clock cycle so it can execute more instructions. SDRAM comes in three flavors (pc100, pc133, pc150). Each is used for different computers with different bus speeds. Next comes RDRAM (Rambus Dynamic RAM). This was expected to be the future of ram since its capable of up to 800mhz and transfer rates up to 1.6 billion bits per second. Due to high prices, noncompatability between motherboards, this didn’t catch on as strongly as was expected. Next in line is DDR RAM (Double Data Rate RAM) which is basically SDRAM that uses both side of the clock cycle to execute instructions. Comes in quite a few flavors (pc1600, pc2100, pc2400, pc2700, pc3000, and pc3200) Each runs a different frequency with lowest being 200mhz and the highest being 400mhz).

There are a couple others but due to their selective use or them never gaining a foothold in the market, I won’t go through them.

But do the numbers in the DDR ram, do they mean anything, or are they just a name?