Rambus revisited in upcoming Abit SI7 board

WE'VE BEEN INFORMED that Abit's upcoming SI7 motherboard will be sampling shortly with channel availability following soon thereafter. The SI7 is built on SiS's RDRAM-equipped 658 chipset and will be targeted for the highest-end of the P4 performance market.

Whether you love or hate Rambus, the SI7 is going to be an interesting piece of work. No company except Intel has ever designed an RDRAM chipset and Intel's last new RDRAM design was launched two and a half years ago in the form of i850. While i850e is only about a year old, that particular chipset is more an update to the original than an all-new design. With Intel leaving the RDRAM market altogether, SiS now stands alone as the sole provider of an updated RDRAM solution—a position the company undoubtedly hopes will prove quite lucrative. SiS 658 is also the only RDRAM chipset on the market to support PC1200, and the first to offer widespread support for 32-bit RDRAM modules (to date; only ASUS had included support for the higher-density RIMMs).

Despite the chipset's updated technology when compared to i850e, motherboard manufacturers have almost entirely avoided the solution. To date, only ABIT has chosen to build a board based on the SiS 658, and has done so acknowledging that the board was a "significant risk" from their point of view. It's the type of move that could end up costing the company a fortune or securing it a virtually-unchallenged market niche. Should the SI7 prove extremely popular, ABIT will have stolen months on its competitors as they build their own 658 solutions—should it fail at market, the entire motherboard and all the costs associated with using a new chipset go down the drain.

There's also been talk that the SI7 may have (unofficial) support for an 800 MHz FSB. If true, this puts SiS in a very interesting position. Intel has not yet released its licensing plans for 800 MHz FSB technology, and rumour has it that Santa Clara would prefer not to licence the technology at all. "Unofficial" support is one way 3rd party vendors have dodged licence restrictions over the years, but Intel has been increasingly harsh lately towards vendors it sees as breaking licensing rules.

On the other hand, even if the SI7 supports an 800 MHz FSB, the board had best support the currently non-existent PC1600 RDRAM standard as well. If it doesn't, SI7 users running on an 800 MHz FSB would find themselves in the unusual position of being far more memory-bandwidth starved then their DDR competitors. Dual channel DDR400 will deliver a full 6.4 Gb/s of memory bandwidth to the P4, while dual DDR 333 offers 5.4 Gb/s. Dual RDRAM PC1200, by contrast, can only offer 4.8 Gb/s—plenty for today's P4's, but far short of what an 800 MHz FSB P4 would need for optimal performance.

With all these issues swirling around it, the SI7 will definitely be one of the most interesting motherboard introductions of 2003. Its SiS's attempt to challenge Intel at the highest levels of P4 performance, ABIT's shot at a unique, popular product, and Rambus' last chance to retain any significant presence in the desktop market. If the SiS 658 / SI7 combination succeeds, we'll undoubtedly see at least a small surge as other motherboard manufacturers try to jump on board the trend—if it fails, Rambus will finally be kicked out of the desktop market altogether. The consumer OEM and retail market has shown very little interest in embracing RDRAM as a mass-market standard—can SiS succeed where even Intel failed?

Time will tell…. µ

See Also
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