I925 vs. I915 vs. I875P
Now we get down to the new chipsets which Intel has intended the new 775 processors to be partnered with. Formally known as Alderwood and Grantsdale, the chipsets are now known respectively as 925x and 915. These new chipsets represents Intel's latest technology advances in both North and Southbridge technologies and the removal of some of our old favourite additions which we had grown to know and love.
- Memory Controller Hub
The i9xx series MCH introduces the first to market DDR-2 memory controller. We saw a lot and heard a lot about DDR-2 at Computex in both 2003 and 2004, today we see it make its was from the drawing board to the consumer market.
Both the i925 and i915 supports a Dual Channel DDR-2 memory controller supporting DDR-2 533 and DDR-2 667 memory technology which represents the next generation in memory technology. DDR-2 is based on the same technology that DDR was first founded on, by using both the rising and falling edges of the clock cycle to transmit in essence 2x the amount of data that SDR memory was ever capable of.
While it is well and good to have a new technology, DDR-2 is simply not mainstream enough at this point in time, and DDR still holds a huge chunk of the memory market. This is why Intel has not totally turned its back on the memory technology that once saved its Pentium 4 CPU from extinction. The i915 chipset (only) also has a second memory controller built-in that is a direct descendant of the i875P chipset in that it supports Dual Channel DDR memory up to 400MHz giving a maximum bandwidth transfer rate of 6.4GB/s.
- Introducing PCI Express 16x
AGP has now reached its peak, and can go no further. Already using an 8x compression system to transmit 8x the amount of data (4x on the rising and 4x on the falling edges of the AGP clock), it has no ability for future design - it simply cannot go any faster.
AGP 8x and 4x performances are about 2% apart, and with a maximum bandwidth of 2.1GB/s, it is not able to keep up with the currant range of video cards and the demands they'll seek in the not-so-distant future.
This is where the new graphics interface of the i9xx series comes in, known as PCI-Express x16. PCI Express (or PCI-E) has been in development for nearly a full year now with Intel, nVidia and ATI already starting to push out PCI-E video cards onto the market, in small quantities. The PCI-E bus is a revamped PCI bus with some major improvements - such as a serial nature rather than the tradition parallel nature as well as independent bandwidth instead of shared. PCI-E 16x uses 16 PCI-E lanes to create a interface supporting a whooping 8GB/s of available bandwidth in both directions for the latest and next generation of video cards to take full advantage of the CPU and memory systems.
I915 series chipsets come in two different flavours - the I915P with discrete graphics (no onboard) and the new I915G with Intel Graphics Accelerator 900. This is Intel's latest in UMA design onboard graphics. Designed to take out VIA's Unichrome Pro and ATI's IGP9100 series graphics, Intel has put its graphics controller interface directly on the PCI-E x16 lane. This allows for the full 8.0GB/s of bandwidth to be used for both data between the CPU and the Memory controller, which is perfect as the onboard graphics needs to use the system memory for its frame buffer.