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• JEDEC standards also dictate standard timings for memory modules as well as the other information covered in Table 1. Memory costs hinge on two different key values, while improvements to these values increase the per-unit price. The first key value is memory latency, which has to do with the delay between initiating a request for memory access (usually by memory location or address) and the time until the data stored at that location is retrieved. Latency is a fundamental measure of memory speed, whereby lower latency means faster memory access. The other key value also involves latency and is generally referred to as memory timing. Memory timing hinges on four performance metrics, listed as follows in order of importance: CAS, usually expanded as column address strobe (or sometimes as column address select), which refers to the column for some physical memory location in an array composed of columns and rows of capacitors used in dynamic random access memory (DRAM) modules (of which all three types of RAM in this guide are sub-types). CAS latency generally appears first in timing sequences for RAM and indicates the number of clock cycles that elapse between when the memory controller instructs the memory module to access a particular column in its current row, and when such access produces the data that resides there. Trcd or tRCD, usually expanded as RAS to CAS delay, where RAS is expanded as row address strobe, where R refers to the row for a physical memory location in an array composed of columns and rows of capacitors used for DRAM modules. This value specifies the number of clock cycles between a Row Address Strobe (RAS) and a CAS, and represents the row address to column address delay for a memory module. Trp or tRP, usually expanded as RAS precharge, which represents the number of clock cycles required to end access to the current row of memory, and commence access to the next row of memory, so that tRP = time for row precharge. tRAS or Tras, usually expanded as RAS access time measured by the number of clock cycles needed to access a certain row of data in DRAM between the initial data request and the precharge command required to commence the next memory access. By definition, tRAS must be greater than or equal to the CAS plus the tRCD, plus an additional two cycles, to leave time for accesses to complete, as they read or write multiple bits of memory, which DDR (2 bits), DDR2 (4 bits), and DDR3 (8 bits) all do in lesser or greater numbers. RAM memory timings usually appear as sequences of four numbers separated by dashes, as in 5-5-5-15. This indicates that the CAS, tRCD and tRP values are all equal to five clock cycles, and that the tRAS value is equal to 15 clock cycles. The smaller the numbers that appear in these sequences, the tighter memory timings are said to be. Likewise, larger numbers are said to indicate looser timings. Simply put, lower latency costs more, tighter timings cost more and the combination of the two costs the most where memory is concerned. RAM Value Versus Performance As we already explained, JEDEC memory specifications set the basis for what kinds of performance and capabilities RAM must deliver. In general, memory that's designed to meet the JEDEC specs but not to exceed them costs the least to design and implement. That's why it's usually the cheapest and is so often used in budget and commercial systems, for which component prices are usually more important than their performance. Memory vendors usually call this kind of memory "value line memory," where low cost trumps other considerations. This explains why value RAM is drab looking, and generally devoid of heat spreaders, fancy logos and even, advertising coverage. If cost is more important than performance, you should buy value RAM every time. If you plan to add memory modules to your PC, buy value RAM if that's what's already installed, otherwise, match performance as closely as possible if you can't buy exactly the same kind as is already in use. On the other hand, performance memory is memory that exceeds JEDEC specifications by deliberate design. As any price check will clearly illustrate, performance memory costs more than value memory - sometimes, indeed, a great deal more than value memory of the same type and speed. Most performance memory not only exceeds JEDEC specifications for timings (by making them tighter); it also exceeds JEDEC specifications for speed (by making them run faster than the maximum speeds defined in those documents). Beyond the maximum JEDEC speed for some type of memory, all faster memory is performance memory by definition. In fact, there are those who might be inclined to argue that all DDR3 memory is performance memory because of its relatively high cost. Technically speaking, however, only DDR3-1800 (and the soon-to-be-released DDR3-2000) memory exceeds the defined DDR3 speed range.

• A New RAM Hard Drive from HyperOs

  Gigabyte certainly created a stir earlier this year when it debuted its i-RAM solid state hard drive composed of DRAM modules. Inside, the i-RAM offers a PCI-type add-in card that hosts four DDR memory modules and hooks up to a mass storage controller via Serial ATA. A battery unit backs up the data stored in the memory when the PC is powered down. The main feature of the i-RAM and RAM-based drives in general is their amazingly short access times and data transfer rates that easily exceed the bandwidth of common hard drive interfaces such as UltraATA or Serial ATA. Shortly after we published our i-RAM review, British vendor HyperOs Systems offered that we test drive its HyperDrive III solid state disk product. The vendor claims the HyperDrive III is superior in many ways, as it offers more memory capacity and comes in a nifty 5.25" form factor. Given their novelty, all solid state disk products have one major drawback: their prices compared to traditional hard drives are out of reach for most budgets. The devices remain far more expensive as measured by price per bits of capacity. However, products such as Gigabyte's i-RAM or the HyperDrive III by HyperOs Systems are priced more competitively since they contain standard components and their memory capacities are limited.

• Pipe Dreams: Six P35-DDR3 Motherboards Compared

  Editor's Note: As mentioned below, Biostar's TP35D3-A7 Deluxe motherboard with BIOS Revision 0.51 would not boot when overclocked even 1 MHz. We obtained a TP35D3-A7 with an updated BIOS. It is discussed here. With support for DDR3 memory and the next generation of FSB1333 Intel Core 2 processors, Intel's P35 Express chipset is the most forward-looking part in its portfolio. But support for advanced technology isn't going to alter its market: The P35 Express is designed to replace Intel's legendary-overclocking P965 mainstream part. Driving Intel's latest technology "downward" into the mainstream is support for only a single PCI-Express graphic card at full x16 bus width and official DDR3 memory support extending only to 1066 MHz data rate. As a mainstream part, the P35 Express officially supports a single graphics card and memory speeds up to DDR3-1066. Adding a second graphics card slot or DDR3-1333 RAM compatibility are features Intel left to the discretion of motherboard producers. The sixteen PCI-Express lanes delivered by the Northbridge are capable of supporting only one device, so there is no option to split them across two slots as previously seen in the high-end Intel 975X and later in the ATI CrossFire Xpress 3200. Like the P965, any second graphics card must instead use some of the six PCI-Express lanes from the Southbridge, so most "CrossFire Compatible" P35 Express motherboards will have the two x16 slots wired with x16 and x4 pathways. Rather than being a true CrossFire solution, any second graphics card is really more useful for adding multiple displays than it is for boosting graphics performance. Great single-card performance and high overclocking capabilities pushed the P965 Express chipset to the forefront of mid-priced performance, so a major part of P35 Express testing will be to make sure this new product lives up to the reputation of its predecessor. Buyers looking to upgrade their motherboard for future processor support while keep their old DRAM modules will be more interested in the P35 Express Chipset's DDR2 capabilities, while others will want to see how DDR3 motherboards compare to DDR2 versions. However, DDR3 still has to mature, and today's modules run such high latency that it makes a fair comparison impossible. Today, we focus on DDR3 performance. We will detail DDR2 performance in an upcoming review, and readers who still need to be convinced that DDR2-1066 CAS4 can be quicker than DDR3-1066 CAS7 can look back to this review for a comparison. Join our discussion on this topic