It is more than six weeks ago now. One day after Intel released its new
It was that day when I started to dig for one of those mystical 'OR840'-boards, or at least another motherboard with this shiny new i840-chipset, that looked so much better than the 'tainted' i820.
The Intel 840 Chipset
The i840 is actually a 'workstation'-chipset and the designated successor of the 440GX-chipset. Due to this, you won't find i840 on mainstream motherboards right now and Intel doesn't really like anyone to talk about i840, who does not address workstation users. However, looking at i840's features and its differences to i820, the RDRAM-mainstream chipset, make i840 appear rather attractive to anyone who wants to use a Coppermine-processor.
On the first look i840 isn't really that different to i820. Both chipsets share the RDRAM-support, AGP4x, the 'accelerated hub architecture' with the 82801 I/O Controller Hub (ICH), ATA66-support, dual CPU-support, and both chipsets sport the 133 MHz front side bus. So far both are the same; the difference are the added features of i840:
- Dual memory channels, operating in lock-step, provide up to 3.2 GB/s of memory bandwidth. Thus i840 has double the memory bandwidth of i820, which is a rather huge difference. The two memory channels can also reduce latency, so that i840's memory interface is way better than i820's. Additional to that, i840 supports up to 2 GB of memory, also double of what i820 can be equipped with.
- Using the optional 82803 RDRAM-based memory repeater hub (MRH-R) or 82804 SDRAM-based memory repeater hub (MRH-S) increases i840's memory capacity even further, but the current cost of RDRAM and the performance loss of using SDRAM with either i820 or i840 doesn't make this option look particularly attractive.
- i840 comes with a special prefetch cache, allowing more efficient data flow and improving system concurrency.
- The optional 82806 64-bit PCI Controller Hub (P64H) supports 64-bit PCI slots at speeds of either 33 or 66 MHz. The P64H connects directly to the MCH using Intel Accelerated Hub Architecture, providing a dedicated path for high performance I/O. This is a feature for workstations indeed, and you won't find it on the less sophisticated i840-motherboards. Mainstream users won't be able to take much advantage of 64-bit PCI-slots, since there's hardly any 64-bit PCI-cards available in the first place and there would also hardly be any need for a 64-bit PCI sound card or network card for normal users.
In short, the main catch of i840 is it's two RDRAM-channels versus only one RDRAM-channel of i820. This increases memory bandwidth and reduces memory latency, but you always have to plug two RDRAM-RIMMs into an i840-board. i840's prefetch cache is another advantage over i820, and you can notice that in more than just workstation software, Quake3 likes to run on i840 as well.