ARM Processor

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The ARM architecture (previously, the Advanced RISC Machine, and prior to that Acorn RISC Machine) is a 32-bit RISC processor architecture developed by ARM Limited that is widely used in a number of embedded designs. Because of their power saving features, ARM CPUs are dominant in the mobile electronics market, where low power consumption is a critical design goal.

Today, the ARM family accounts for approximately 75% of all embedded 32-bit RISC CPUs,making it one of the most prolific 32-bit architectures in the world. ARM CPUs are found in all corners of consumer electronics, from portable devices (PDAs, mobile phones, media players, handheld gaming units, and calculators) to computer peripherals (hard drives, desktop routers). Important branches in this family include Marvell's XScale, the Texas Instruments OMAP series, Samsungs S3C24xx series, and NXP's Bluestreak series.


TECHNICAL INFORMATION

CPU Core MMU/MPU ISA
StrongArm MMU v4
ARM7TDMI none v4T
ARM7EJ-S none v5TEJ
ARM720T MMU v4T
ARM920T MMU v4T
ARM922T MMU v4T
ARM926EJ-S MMU v5TEJ
ARM940T MPU v4T
XScale MPU v5TE
ARM946E-S MPU v5TE
ARM966E-S none v5TE
ARM1020E MMU v5TE
ARM1022E MMU v5TE
ARM1026EJ-S MMU+MPU v5TE
ARM1136J-S MMU v6
ARM1136JF-S MMU v6
Cortex-M1 none v6-M
Cortex-A8 MMU v7-A
Cortex-R4 MPU optional v7-R
Cortex-M3 MPU v7-M


CPU Core Pipeline Depth Typical MHz
ARM7 3 stage 80
StrongArm 5 stage 133
ARM9 5 stage 150
ARM10 6 stage 260
XScale 8 stage 400
ARM11 8 stage 335

NOTE: increased pipeline length reduces the amount of work done at each stage in the pipeline, therefor enabling higher operating frequencies and performance. however, as the pipeline length increases, system latency also increases due to increased number of clock cycles needed to fill the pipeline before an instruction can be executed. an example would be an ARM920T running at 400MHz might have comparable performance to an Xscale running at 600MHz