ARM assembly language compatibility

fox68k · Post by **fox68k** » Fri Oct 15, 2004 3:04 pm

Hi,

i am thinking about programming for the ARM processor inside the DC in assembly language, but i would like to know if the assembly language for this processor (ARM7) is compatible (this is, i can run the same assembly code) with, for example, the ARM9 inside the GP32.

In addition, what are the differences between these processors? What are the similarities? And with other ARM processors?

Thanks in advance.

Alexvrb · Post by **Alexvrb** » Fri Oct 15, 2004 10:48 pm

The ARM7 in the DC is I think an ARM7TDMI. That means v4 architecture, maybe v4T? If it supports Thumb code, its a v4T, if not, just v4. I'm pretty sure the ARM9 in the GBA is v4T, which means ARM and Thumb code compatible. Anyway, anything you write for the ARM in the DC should work on the GBA's ARM, but not necessarily the other way around. Thumb code requires logic that decodes the instruction on-the-fly to full ARM code. As for similarities between ARM CPUs, they're all very similar, but they are just becoming more and more advanced. Extra capabilities are added that the older chips did not have. ARM7 and ARM9 are pretty close, though it varies from core to core (because there is no single ARM7 design or ARM9 design).

BlackAura · Post by **BlackAura** » Fri Oct 15, 2004 11:18 pm

As far as I know, the ARM7 in the DC doesn't have thumb mode. It's also pretty slow, largely due to sharing a bus and memory with the sound hardware. When the sound hardware needs access to SRAM, the ARM7 can't do anything. So it runs pretty slowly.

bender · Post by **bender** » Sat Oct 16, 2004 4:44 am

I read somewhere that the ARM7 could be easily overclocked via software (up to 100mhz, i think). I understand that the problem of using the ARM7 it's more about the SRAM than the ARM7, just wanted to post because i don't know if it could be useful

Alexvrb · Post by **Alexvrb** » Sat Oct 16, 2004 5:06 pm

BA, is there any way you could cut back on sound hardware accesses to SRAM, to give most of the time to the ARM?

BlackAura · Post by **BlackAura** » Sat Oct 16, 2004 9:02 pm

You could turn off the sound hardware, but that's kinda pointless. The only part of the Dreamcast that the ARM can do anything with is the sound hardware.

Ex-Cyber · Post by **Ex-Cyber** » Sun Oct 17, 2004 11:18 pm

Shouldn't the memory accesses scale with how many channels are enabled?