Brooktree

~ the last words ~

Rockwell bought Brooktree in 1996 and the name stopped being a company, though it went on being a part number for years. Rockwell spun its semiconductor division out as Conexant in 1998, and Conexant shipped one more chip in the line before the family stopped: the Fusion 878A, which added MPEG-2 and digital broadcast decode by reusing the pins the previous generation had used for audio. The company that had designed all of it no longer existed by then.

Henry Katzenstein had the idea in Los Angeles in 1981 and set the company up in San Diego in 1983 on venture money, naming it after a street he used to live on. The idea was about switching. A digital to analog converter driving a monitor has to change its output fast, and the conventional approach switched voltages, which capped most systems around 25 MHz and dumped electrical noise back onto the power supply every time it flipped. Katzenstein's design mixed two current sources instead, so the input power stayed full on and only the output varied. The noise went away. The penalty was that the chip drew its full power constantly and dissipated it as heat, which Jon Peddie's history of the GPU records as hot enough to burn you.

The videoDAC reached the market in 1985 running at 75 MHz, roughly four times the speed of what else was available, far enough ahead that it could drive a display 2,048 pixels wide at 60 frames a second. Nothing on sale needed that yet. Mass production did not start until 1988, when monitors at that resolution finally appeared, and then the design took market share off Analog Devices and Texas Instruments at speed. Apple and Sun were customers.

~ the record ~

~ the ramdac years ~

The follow-up changed one thing. Instead of a fixed table mapping stored pixel values to output colors, the table could be written to, so the same stored value could be green under one program and blue under another. Brooktree's own word for the thing was RAMDAC, and the part is also called a LUT-DAC. Both names outlived the company. For a few years this was the chip that made a workstation's screen look like a workstation's screen.

Then fabrication caught up. Once a manufacturer could fit the lookup table onto the same die as the rest of the display controller, there was no reason left to buy a separate converter, and the business Brooktree had been built on thinned out underneath it. The company had already begun hunting for a second act.

~ the tv card ~

Somewhere in the early nineties Brooktree put out the Bt848, which took the output of a radio frequency tuner and produced a digital stream a PC could compress and store. A European variant pulled teletext out of the signal as well. The Bt878 followed with audio decoding built in, FM radio included, sampling at CD rates and cutting the number of chips a complete television decoder needed.

That chip is the reason this company is worth a grave. From about 1995 onward the TV tuner card was a standing item in computer shop price lists, sitting somewhere below the sound card, and in Turkey it was the cheapest way to get a television into a room that already had a monitor in it. Hauppauge sold them under its own name and the cheap ones carried a brand nobody had heard of before or since. Whatever the sticker said, the part doing the actual decoding was usually a Brooktree.

~ how the name went ~

Nobody wrote a shutdown notice for this one and there is no final day to point at. Brooktree was bought, and the name went quiet in the ordinary way an acquired semiconductor company's name goes quiet, which is that the business cards change and the chips keep shipping under the old part numbers until somebody decides otherwise. The Bt prefix stayed in driver lists and hardware documentation for years after there was any Brooktree left to ask about it.

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