The Memory Controller: 32-bit LPDDR1
The Lincroft SoC (or Atom Z600) measures 13.8 mm x 13.8 mm x 1.0 mm. That’s smartphone SoC sized. In order to hit the small package size and in order to keep power consumption down, the single channel DDR2 memory controller from the netbook Atom is gone. What we have instead is a 32-bit wide LPDDR1 memory bus capable of supporting up to 1GB of memory. At 400MHz that’s about the amount of memory bandwidth we had on PCs 10 years ago.
Intel claims that the majority of workloads on smartphones are compute and not memory bandwidth bound so the reduction in memory bandwidth isn’t going to be an issue. Lincroft's caches are the same as Silverthorne before it (24/32KB L1 + 512KB L2).
Compared to smartphone SoCs today, Intel isn’t really outgunned:
| 2010 Application Processor Comparison | |||||
| Memory Interface | |||||
| Apple A4 | 32-bit LPDDR1/LPDDR2 (?) | ||||
| Intel Atom Z600 | 32-bit LPDDR1 | ||||
| TI OMAP 3430 | 32-bit LPDDR1 | ||||
| TI OMAP 4430 | 2 x 32-bit LPDDR2 | ||||
| NVIDIA Tegra 2 | 32-bit LPDDR2 | ||||
| Qualcomm Snapdragon QSD8250 | 32-bit LPDDR1 | ||||
It’s only next year when products based on TI’s OMAP 4430 chip that we’ll see a real ramp in memory bandwidth. Intel will offer a version of Lincroft for tablets with a 32-bit DDR2-800 interface. It can support a maximum of 2GB of memory.
The Lincroft memory controller has less bandwidth than the netbook version, but it's more efficient as a result. Intel included a lot of optimizations, particularly for graphics to improve bandwidth utilization.
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