Last month Cradle introduced the CT3600 family, the successor to its original CT3400 chip. The CT3600 family—which includes the CT3608, CT3612, and CT3616—will offer major improvements over the CT3400 in the areas of parallelism, clock rates, and on-chip integration. Like the CT3400, the CT3600 family will primarily target digital video applications, particularly multi-channel surveillance applications.
The CT3600 will use essentially the same architecture as the CT3400. This heterogeneous architecture combines several DSP cores and several general-purpose cores inside the same chip. In the parts announced so far, there are two DSP cores for every general-purpose core.
The main difference between the CT3400 and the CT3600 is the number of cores per chip. The CT3400 includes eight DSP cores, while the CT3600 will include up to sixteen DSP cores. The names of the CT3600 parts indicate the number of DSP cores included in the chip: the CT3608 will include eight DSP cores, the CT3612 will include twelve, and the CT3616 will include sixteen. In addition to the increase in parallelism, the CT3600 increases the maximum core clock speed to 375 MHz, compared to 230 MHz for the CT3400.
It is difficult to directly compare the CT3600 to mainstream DSPs, but it appears that the CT3600 will offer a level of performance that is competitive with today's fastest DSPs. Cradle claims the 375 MHz CT3616 will be able to encode 16 channels of MPEG-4 Simple Profile Level 3 video at CIF resolution and 30 frames per second. Cradle also claims that the 375 MHz CT3616 will be able to encode H.264 Main Profile video at D1 resolution and 30 frames per second. Few existing embedded processors can handle either of these video loads.
The CT3600's on-chip integration is also notable. The CT3600 family members include much more memory than the CT3400 does. For example, the CT3616 includes 400 Kbytes of memory, nearly double the memory on the CT3400. The CT3600 family also upgrades the CT3400's SDRAM interface to a 333 MHz DDR memory interface, and it adds a 66 MHz PCI interface.
One area where the CT3600 does not make improvements is programmability. Multi-core processors—particularly heterogeneous multi-core processors—are notoriously difficult to program. Adding cores to the architecture will only increase the complexity of the programming model. Fortunately, Cradle is targeting multi-channel applications where there are obvious ways to use multi-processor parallelism. In addition, Cradle says it will provide key software components such as video codecs and IP stacks.
The CT3616 is expected to begin sampling in June. The CT3612 and CT3608 are expected to begin sampling in the third quarter of this year. When ordered in 10,000-unit quantities, pricing is expected to range from $40 for a 230 MHz CT3608 to $91 for a 375 MHz CT3616.
For more on these parts, see "Cradle, Freescale, TI to debut DSP products at ESC" and "Programmable DSP family boasts up to sixteen 375MHz DSP engines."