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On Wed, 2005-08-17 at 15:43, Steven Scholz wrote:
Richard,
Thanks a million. Maybe you could explain the difference of arm920t and arm9tdmi as well, please?the arm920t is an armv4t device (the 't' is thumb).Thanks for googling for me! ;-)First google hit on "AT91RM9200": http://www.atmel.com/dyn/products/product_card.asp?part_id=2983
That page mentions that it's an ARM920T core. First google hit on "ARM920T": http://www.arm.com/products/CPUs/ARM920T.html
That page mentions 'ARMv4T'.
So I use either -march=armv4 _OR_ -mcpu=arm920t. Right?
(Using both brought me a warning about conflicting).
Basically, there are two options, -march=xxx and -mtune=xxx that are independent (one selects the available instructions, the other the best way to use that set for the intended cpu). -mcpu=xxx is shorthand that can be used to set both options in one go: so -mcpu=xxx is equivalent to writing -march=<arch_of(xxx)> -mtune=xxx.
Note that to get Thumb code you have to use -mthumb; it's not sufficient
to tell the compiler that you have thumb instructions available.
The arm9tdmi is the main 'core' of the CPU. The arm920t is the core plus the associated cache, mmu, and system registers. Different models all have substantially the same 'core' but may have different (or missing) additional parts. Thus arm920t arm926t arm966t etc.
It's not quite as simple as that (for marketing reasons), but that's the one paragraph summary.
See the ARM web site for more details of the different products
(www.arm.com).
"T" variants: Thumb instruction set support. "M" variants: Long multiply instruction support (32x32->64 and 32x32+64->64) "E" variants: DSP-related instruction support.
"D" on-chip debugging unit. "I" EmbeddedICE hardware suport.
-- Bill Gatliff bgat@billgatliff.com
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