Printable View
I don't think anyone has really figured out how to get decent speed from the ARM anyway. There have been some theories, but I've never seen anyone get it to perform as anything more than like a ~5Mhz ARM, if that.
Hola, you do realize that the bus to sound memory, even if you could get that to work, would be too slow if you needed to use the SH4. But I don't think that would work anyway? You could instead borrow memory from the sound/video RAM to store parts of a ROM, perhaps.
[quote author=Alexvrb link=board=dcemu;num=1091972704;start=0#10 date=08/16/04 at 00:47:55]I don't think anyone has really figured out how to get decent speed from the ARM anyway. There have been some theories, but I've never seen anyone get it to perform as anything more than like a ~5Mhz ARM, if that.
Hola, you do realize that the bus to sound memory, even if you could get that to work, would be too slow if you needed to use the SH4. But I don't think that would work anyway? You could instead borrow memory from the sound/video RAM to store parts of a ROM, perhaps.[/quote]
Its a 24Mhz ARM that is overclockable to 100, why would that be so slow? Also, everybody says the sound bus is super slow, but that is only relative to the rest of the hardware, what really matters is whether or not its faster than the GBA hardware.
[quote author=Alexvrb link=board=dcemu;num=1091972704;start=0#10 date=08/16/04 at 00:47:55]I don't think anyone has really figured out how to get decent speed from the ARM anyway. There have been some theories, but I've never seen anyone get it to perform as anything more than like a ~5Mhz ARM, if that.
[/quote]
your joking right? arm is some fast stuff... even i know that. and i dont know anything.
[quote author=1timeuser link=board=dcemu;num=1091972704;start=0#12 date=08/16/04 at 06:51:59]
your joking right? arm is some fast stuff... even i know that. and i dont know anything.[/quote]
He means getting the equivilant of 5Mhz out of the Dreamcast's ARM sound chip. The way that it is structured divides the effective clock speed down by a lot, because even though it works at 24Mhz, it can only be sent new data very slowly... or something like that.
plus the traffic for sound going back and forth across the bus would be competing for the resources.
Quzar, you can't argue with me and against me at the same time buddy. It just confuses people. :P
Go ahead and compile something for the ARM in the AICA. The GBA's ARM is only clocked at 16Mhz, so you should at least get that kind of performance, right? Â*;D
Edit: I actually got a reply from Neill on the matter:
On Mon, 16 Aug 2004, Alex wrote:
> Do you happen to know what the ARM in the DC's AICA is (capable
of
> being?) clocked at?
2822400 Hz.
> Something about it sharing time with the rest of the sound
subsystem?
The effects DSP is only allowed access to main memory every other
cycle,
and it runs at 5644800 Hz (44100 * 128 ), so I guess the CPU gets the
other
half.
Neill
The arm is however software overclockable. you can send a command to it that will set the speed to anything between 1 and 100 Mhz
[quote author=quzar link=board=dcemu;num=1091972704;start=15#16 date=08/16/04 at 21:04:16]The arm is however software overclockable. you can send a command to it that will set the speed to anything between 1 and 100 Mhz[/quote]
Any one know the command to do that?
ugh, i dont know it off the top of my head. I have seen it in some AICA documentation and i posted the excact thing over at DCemulation. Give me a bit and ill find it...
Whew, i finally found it...
The speculatory parts of those are me.Quote:
according to "Yamaha AICA Sound System Hardware Reference v0.8" You can change the clock rate of the arm chip through the interrupt/timer register 0x28a8 which is set to the desired clock speed - 1. The examples this document give are 00 = 1Mhz and 24 = 25Mhz. Using this you could theoretically clock this higher, to 16 Mhz, 32 or probably even 64 without causing any permanent damage. I assume that what is happening is that it defaults to 3Mhz (~2.8) because that is the minimum required by the AICA but it is probably possible to go much higher than that (probably up to 25Mhz as sega notes) safely.
You can find a HUGE post of info about the ARM by heliophobe here: http://www.dcemulation.com/phpBB/vie...&start=200
along with that are my post in response, and some insightful randisms (read his first post after mine on that page hehe)
Edited to fix the quotes. YaBB doesn't handle quotes like phpBB, so you can't just enter a user's name with the quote (yet).
is this project open source?