Yet another bus war, coming to a handset near you
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It seems like a long time ago in a job far far away, but I do remember the infamous memory bus wars between Rambus DRAM (RDRAM) and the Synchronous Link DRAM (SLDRAM) interface. At the time, both were going to save the day by alleviating the bottleneck between CPU’s and DRAM on motherboards. As so often happens, the winner (RDRAM) was ultimately determined by allegiances, market clout, and politics more than technical merit. Once Intel threw its weight behind Rambus, SLDRAM quietly sulked it’s way to wherever all those Beta video tapes went. Of course we all know that RDRAM died a couple of years later but that’s another story.
Fast forward a couple of years and another bus-war emerges, pitting RapidIO against PCI-Express. Both replace traditional Northbridge chips with switching fabrics, sometimes integrated into the CPU. I won’t put my neck out and pick a winner for fear of losing friends. Let’s just say I know which side the borg, I mean, Intel is on – “resistance is futile”! RapidIO will probably enjoy healthy “niche” status in PowerPC systems, likely in the comms space primarily.
As someone once said, “the beauty of standards is that there are so many to chose from”. A new bus-war has emerged, this one in the mobile space rather than the desktop/server market. The companies who market display drivers and LCD controller ICs today are enjoying all the pleasures (high volumes) and pitfalls (low margins) typical of a mass market. Display driver IC volumes are now comparable to many memory types – just think a moment about how many DRAM chips versus display drivers you personally own. There are probably ten to fifteen in your computer monitor alone. Add to that your new flat panel TV, a couple of cell phones, your MP3 player, your car’s navigation system, and you own a lot of display driver ICs.
There are many features that used to differentiate these chips in the market; things like internal display RAM, picture-in-picture, fancy gamma correction, and integrated secondary display drivers, not to mention pixel density and colour depth of course. The problem is that these design elements are largely digital and easily integrated into the next spin.
Recent standards have emerged that seek to address a significant design challenge in mobile phones: The interface between the controller IC and the display driver circuits, which is often through the hinge of clamshell phones. All these new intra-panel interconnects are designed to send more bits (pixels and colours) over a narrower interface, reducing the amount of chip-chip interconnect between the controller and the panel, reducing the size of the bezel around LCD displays, and perhaps most importantly, reducing system costs.
In April NEC announced with the launch of their µPD106290 240RGB source driver with a whopping 68 billion colours (12 bit). The new driver uses an interface called Point-Point mini-LVDS (PPmL), which has also been embraced by TI and Thine for their timing controller chips. This is presumably to replace the “Current Mode Average Differential Signalling (CMADS) scheme announced by NEC in 2004. The first CMADS drivers were launched in November 2005, and the first handsets just reached production in February of this year on the NEC FOMA N902i handset. This tells you something about how long it takes a newly announced standard to appear in the palm of your hand.
The NEC announcement follows February’s announcement by Qualcomm that many of their CDMA chipsets will incorporate the Mobile Display Digital Interface (MDDI). Seiko-Epson, Toshiba, and Renesas have hitched themselves to that wagon with display drivers that communicate across this new, narrow link.
Both NEC and Qualcomm are of course, trying to outdo National Semiconductor, who appears to have good traction with their “Point-to-Point Differential Signalling” (PPDS) scheme launched last October. It has since been licensed by ST Microelectronics, Magnachip, Sharp and HiMax.
And of course, don’t forget last month’s announcement by Solomon Systech, launching their first products with the “mini-RGB” interface. At this point mini-RGB only supports QCIF formats (176RGB x 144 to 220), so I think it falls a little bit short.
PPDS, mini-RGB, MDDI, CMADS, PPmL. M-O-U-S-E. I think the winning display driver company will be the one who comes up with a multi-lingual interface, since they all appear to be based on some variant of differential LVDS signaling. Time will tell. It would all be so easy to predict if Intel made cell phones.
I bet if Sony had used RDRAM and RapidIO in their video cassette recorder architecture, Beta would’ve won. Perhaps not.
Thank you for providing up to date information in regard to NEC’s new LCD. From a consumer point of view, I think that all LCD display should have the screen reading capability with high resolution for example: We should be able to point at the screen’s icon with a pointing device and being able to navigate to wherever we want to get to without typing it in. I think keyboarding should be used as a second option. This is just my opinion as a consumer only.
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