Questions about the Broadway CPU
- Thread starter Flux
- Start date
I would be shocked if Broadway could pull off 48GFLOPs, even in Single Precision. A single-core CPU clocked at 730MHz is more likely to be pumping out 4.8GFLOPs than 48GFLOPs.
It just had a little 485 MHz low-cost PowerPC G3 variant (750CXe) with some basic SIMD capabilties. One site says ~ 1.94 GFLOPS (4 floating point ops per clock). Probably a unlikely peak. It's not really a stunningly robust little CPU. Simple, very cheap and yet fairly effective.
As for Broadway, well who knows. The fact that it's very, very tiny though and clocked so low tells me that it's probably just about the same thing but on a smaller process.
As for Broadway, well who knows. The fact that it's very, very tiny though and clocked so low tells me that it's probably just about the same thing but on a smaller process.
Last edited by a moderator:
Vitaly Vidmirov
Newcomer
http://en.wikipedia.org/wiki/Nintendo_GameCube#Hardware_specifications
486MHz * 2 MADD per cycle = 1944 MFlops
It's really stunningly robust, especially when you compare it to it's 4.4x higher clocked, but brain-damaged PowerPC brethren.
I'm guessing the Broadway's FP performance is 1.5x the Cube's FP performance, for obvious reasons.
Color me Dan
Regular
What do you mean by this quote if I may ask? Again i'm no expert but I wasn't aware the G3 was 64bit, if it was wouldn't that increase memory handling efficiency dramatically compared to GC? Well, overall performance too in alot of tasks I guess.
The Wii GPU is still a mystery is it?
The G3 family of processors are 32-bit, using the usual definitions of these things outside console space. 32 vs 64-bitness has no bearing whatsoever on the CPU in the Wii, 64-bit pointers is not likely to be high up on the "desired features" list.
The Wii GPU is still a mystery insofar as no tech docs have been leaked, and the chip is far too large to be just a die shrink of the GC GPU.
While the cost conciousness of Nintendo implies that the die area isn't there without reason, those reasons aren't out in the wild yet. Developers have been mentioning things that imply that fillrates have increased more than clocks, but that's as far as it goes at this point in time.
Early development kits almost certainly used higher clocked GC GPUs in order to get development started and the Wii remote into the hands of developing houses. All early development took place on GC generation hardware/software assets. Still, we haven't any indication that the Wii GPU includes new programmability features, indeed all interviews made point towards the same basic pipeline as in the GC being in place.
This thread was about the CPU though, and IBM has published a pdf on it. It is a very decent performer for its power draw and process technology. Not a theoretical GFLOPS monster, but that doesn't seem to hurt it much in real life. Furthermore, it is surrounded by a pretty sympathetic memory subsystem for its processing power. Since it is so small, and draws so little power already, I'm not sure Nintendo will ever bother to move it down to finer lithography.
Well, no and no. 64-bit addressing allows for a larger memory but that's irrelevant here. It doesn't increase memory efficiency as such. As to performance, 64-bit operands consume more cache space and bandwidth; while having them doesn't do much anything for performance. (Unless you really need to crunch big numbers. SIMD is a different matter but it typically uses FP registers anyway, so doesn't relate to a CPU's "bitness".)
64-bitness when you don't need the big values just costs you bandwidth, cache capacity, and lots of transistors.
If you got the performance increase idea from AMD64, there it happened mostly because AMD64 added new registers to the desperately register-starved 386 baseline, not for the 64-bitness as such.
Last edited by a moderator:
If so what was the point of making Broadway a 64 bit chip instead of a 32bit chip?
The SIMD unit is the same one that is in the Xbox360's PPEs. 128 bit SIMD unit.
Color me Dan
Regular
Thank you for that thurough answer Entropy, I wasn't aiming at comparing 32bit to 64bit though so no worries there. Both have their strenghts and weaknesses in relation to their tasks. No, I got a bit confused by Flux's first post and thought I had to ask (in no way an insult to you Flux).
Broadway is not a direct decendant of Gekko but related to it as I understand it from reading about it on Wikipedia. If there is anyone with more knowledge about it's internals compared to Gekko i'd be very happy to hear about it.
Broadway is not a direct decendant of Gekko but related to it as I understand it from reading about it on Wikipedia. If there is anyone with more knowledge about it's internals compared to Gekko i'd be very happy to hear about it.
Just remember that Wikipedia is a warground for "edit wars" on "hot" topics such as new-ish consoles. You get lots of wishfully-thinking fanboy posts over there. They don't know more than some of the folks there, that's for sure.
Consider that Wii is backwards compatible with Cube so thoroughly that its hardware can probably only be a descendent of GC. It doesn't have anywhere near the performance to emulate a Cube, but it plays such games as well as its predecessor. Its system architecture certainly is reminiscent of Cube just from looking at the machine's RAM layout.
Consider that Wii is backwards compatible with Cube so thoroughly that its hardware can probably only be a descendent of GC. It doesn't have anywhere near the performance to emulate a Cube, but it plays such games as well as its predecessor. Its system architecture certainly is reminiscent of Cube just from looking at the machine's RAM layout.
Not true.
Color me Dan
Regular
Hehe, Very true. But it does give you a general idea of things. I really hope we will get to know details soon, not because I think it makes a difference but because it is teasing my mind that we don't.
IBM PowerPC 750CL Microprocessor PDF
http://www.eembc.com/Press/PressRelease/070314.htm
http://blog.newsweek.com/blogs/leve...amecube-one-point-five-yes-says-beyond3d.aspx
Note how incredibly tiny the "Broadway" CPU die (right) is.
Last edited by a moderator: