Closer Look at Intel X38
Intel X38 chipset was initially intended as new core logic set for expensive mainboards. In fact it implies that X38 came to replace the pretty old i975X that doesn’t officially support promising 45nm Penryn processors and comes with a not very up-to-date South Bridge. At least, according to Intel.
We believe that the situation should be regarded a little bit differently. i975X that has been out there for a considerable while now, it is not longer appealing to computer enthusiasts who have turned to Intel P35 based mainboards these days. The only trump of the i975X chipset - support of Crossfire as PCI Express x8 + PCI Express x8 – is actually not such a great advantage at all. First, Intel P35 chipset can also support Crossfire (although as PCI Express x16 + PCI Express x4). Second, AMD’s contemporary graphics accelerators are not as fast as Nvidia ones. Therefore, there are very few users who would be interested in building a Crossfire system. Summing up all these arguments, we decided not to compare the new Intel X38 against the i975X. Instead we will take the recently announced Intel P35 as its primary opponent, because it boasts close functionality but at the same time can be used to build a little less expensive mainboard solutions.
Intel X38 chipset is very similar to Intel P35. Namely, it features traditional dual-hub architecture and comes with the same ICH9 South Bridge that you can clearly see from the flow-chart below:
The main peculiarity of the Intel X38 chipset is the support of two PCI Express x16 graphics card slots each having 16 “real” PCI Express lanes. This is the first Intel chipset boasting this feature. In other words, Intel X38 supports the fastest modification of AMD Crossfire technology. As for the SLI technology implementation on Intel based mainboards, Nvidia continues to provide no support for it in the drivers, although nothing on the hardware level prevents this technology from working perfectly fine on Intel X38 based platforms.
Support of two PCI Express x16 busses in Intel X38 North Bridge may allow mainboard makers to layout three PCI Express x16 slots on a single board. Although the third slot will be connected to the PCI Express x4 bus via the South Bridge, this shouldn’t hinder simultaneous support of three graphics cards working in Triple crossfire configuration that is due for official release next year.
The new Intel North Bridge acquired not only more PCI Express lanes. Now it also supports faster graphics bus: PCI Express 2.0. In practical terms it stands for double the bandwidth. Now PCI Express x16 slots feature 8GB/s bandwidth in each direction. However, you will need graphics cards supporting this interface to be able to really enjoy this speed in reality, and they are not available in the market yet. PCI Express 2.0 specification implies full backward compatibility with the old graphics cards that is why Intel X38 based mainboards can work absolutely fine with all previous generation graphics solutions as well.
Even though most innovations introduced in Intel X38 deal with the graphics bus, there are a few new things about the SDRAM support as well. Although the Intel X38 memory controller is compatible with DDR2 as well as DDR3 SDRAM, it is not very much different from the memory controller of Intel P35. The newer chipset acquired XMP (Extended Memory Profiles) technology support. It is somewhat similar to Nvidia EPP (Enhanced Performance Profiles) Intel introduced for DDR3 SDRAM. In fact, it implies SPP extensions with information needed to use these memory modules for overclocking needs. Corresponding profiles added to the SPD bear the info on frequency, voltage and timings settings.
These are about the only differences between X38 and P35. However everything we have just mentioned turned out more than enough to require significant changes in the North Bridge of the new core logic. Of course, it affected the heat dissipation in the first place. The Intel X38 North Bridge features 36.5W typical heat dissipation, while the same characteristic for Intel P35 equals only 16W. Although the new chipset is manufactured using pretty up-to-date 65nm production process, the high TDP forced Intel to equip the chip with the same type of a heat-spreader lid that we have only seen on CPUs and server chipsets before.
Intel X38 chipset costs $50, which is about $20 more than the price of Intel P35. For end-users it means that the mainboards based on it will hardly be any cheaper than $200 a piece. To make proper justifications for such high price let’s compare the Intel X38 and Intel P35 specifications side by side:
Here I would only like to add that Intel is going to release an enhanced modification of its X38 chipset in the near future, which will most likely be called X48. The key feature of this chipset will be official support of promising Penryn processors with 400MHz bus. However, I have to be fair and say that high-quality mainboards built on Intel X38 and Intel P35 can mostly work just fine with these processors already.