You can’t always get what you want,
But if you try sometime,
You get what you need.
Those lyrics from a song from the Rolling Stones describes the situation with ASICs/SOCs and FPGAs. For low power, you want an ASIC or SOC. However, there are huge obstacles to using an ASIC or SOC. First, you need a team that knows how to design custom silicon or you need to rent one—which is expensive. If you have your own design team, you should be prepared to drop a million dollars or so on design tools and another million or so on NRE charges. Also be prepared for a 6-18 month design cycle, lots of painstaking verification, and the risk of at least one silicon respin due to design errors or spec changes. High risk indeed.
On the other hand, there are FPGAs. The NRE cost is zilch. The design tools are low-cost or no-cost. There’s no physical chip design required, hence a lot less verification. In short, it’s much easier to design a system based on FPGAs than on SOCs or ASICs, but there’s a price to pay: higher unit cost, less performance, and higher power consumption. All three figures of merit are 10-20x out of whack for FPGAs versus ASICs/SOCs. In addition, you’ll not get the same maximum gate count in an FPGA, not by a long shot.
So if you need an ASIC or SOC, then you need one. If not, and if an FPGA’s part cost, power consumption, and/or performance aren’t where your design needs to be, there is a middle ground. In the recent past, this middle-ground component has been called a “structured ASIC.” That’s become a tarnished name. In the distant past, the name for a similar sort of device might be called a “gate array.” Today, eASIC calls it a “new ASIC.”
What’s a “new ASIC”? If it’s an eASIC Nextreme or Nextreme2, then it’s a predesigned field-of-LUTs device with a preconfigured routing fabric on the metal layers. The only unconfigured layer is the via 6 layer. Standard Nextreme wafers are processed to metal layer 6 and stored. When a design is sent in, the via 6 and metal 7 and 8 layers are added. Depending on how fast the part needs to be made, the via 6 layer is customized using either direct-write e-beam or a standard lithographic mask and then the standard metal 7 and 8 layers are added on top.
So, what do you get from this technology? You get a zero-NRE, FPGA-like device that has much higher silicon density than an FPGA because there are no switches or configuration RAM cells in the routing fabric—just fast, tiny layer-6 configuration vias. Consequently, you get a chip that can clock faster than an FPGA—250 MHz (typical) for a 90nm Nextreme New ASIC and 500 MHz (typical) for a 45nm Nextreme2 “new ASIC.” You get a device that operates at lower power than an FPGA and you get a device that offers more gates/chip at lower component costs (but not as low as for an ASIC/SOC). You also get a chip that’s easier to design than an ASIC/SOC and one that can be delivered in as little as 4 weeks. Design-tool cost is lower than for ASICs/SOCs as well because eASIC offers a specialized, Nextreme-specific version of Magma’s design tools for as little as $8k per seat.
What are Nextreme parts used for? I asked Jasbinder (Jazz) Bhoot, eASIC’s VP of Worldwide Marketing, that question. His answer was both interesting and a bit surprising:
- Cell phone microprojectors (where cost and power dissipation are critical)
- Other microprojectors
- Medical devices such as ultrasound imagers where power is not so much of a problem but device cooling is a big problem
- Portable medical devices that run on batteries
- Wired networking products where Nextreme parts are consolidating several FPGA designs into one chip with much lower power consumption