At the Microprocessor Forum last month, Renesas and SuperH debuted the latest processor in the SuperH family, the SH-X. The SH-X is a synthesizable 32-bit fixed-point CPU core that is object-code compatible with its 32-bit predecessors, which include the SH-3, SH3-DSP, and SH-4. Renesas expects to begin shipping SH-X-based chips in early 2004. It is not yet clear whether the core will be available for license; SuperH Inc., which is responsible for SuperH core licensing activities, did not announce any licensing plans at MPF.
As might be expected based on its object-code compatibility, the SH-X core is architecturally quite similar to its predecessors. The SH-X instruction set is the same as that of the earlier SuperH cores, and the architecture is quite similar to that of the SH-4 except that it has a deeper pipeline (seven stages vs. five). Like the SH-4, the SH-X is a dual-issue superscalar machine.
Renesas will be using the core in two new chips: a low-power chip that targets mobile applications and a high-performance chip that is intended for use in car information systems. In the low-power chip, the SH-X core is augmented with the “DSP unit” from the SH3-DSP. In the high-performance version, the core includes the floating-point unit that is used on the SH-4. The low-power SH-X chip is expected to execute at 200 MHz; the high-performance chip is expected to execute at 400 MHz. Both will be fabbed in a 0.13-micron process and are expected to offer lower power consumption than previous SuperH chips.
At 400 MHz, the high-performance SH-X chip will be much faster than Renesas’ current SH-4-based offering, which runs at a maximum clock speed of 240 MHz. The low-power chip will execute at roughly the same clock speed as current SH3-DSP chips, but will offer higher DSP performance because of the SH-X’s superscalar architecture (the SH3-DSP is a scalar machine) and will also yield lower power consumption.
The BDTI Benchmarks™ show that the SH3-DSP and SH-4 themselves provide quite respectable DSP performance, with BDTImark2000™ scores of 750 at 240 MHz (SH-4, using floating-point code) and 490 at 200 MHz (SH3-DSP, using fixed-point code). For customers already using these processors, the new SH-X chips will provide a welcome step up in performance and power efficiency. The SH-X will likely compete well for new sockets, too, as it is among the faster 32-bit embedded processors currently available.
Add new comment