MAD147":1lyzosel ha detto:
Ma quindi c'è pure sul 3g?
sì.
Ma le differenze hardware sono:
"The iPhone and iPhone
3G use a system on a chip (SoC) f
rom Samsung. The SoC is a custom part and actually has Apple’s logo on the chip. The SoC houses the CPU, GPU and memory for the iPhone. The CPU is based on the
ARM11 core, in specific it is the
ARM1176JZF-S. The CPU runs at 412MHz to save power, although the core is capable of running at 667MHz. The ARM11 CPU is a single-issue in-order microprocessor with an 8-stage integer pipeline. It’s got a 32KB L1 cache (16KB for instructions, 16KB for data) and no L2 cache. The ARM11 CPU in the iPhone also has a vector floating point unit, but thankfully the SoC includes a separate GPU for 3D acceleration. You can think of this core as a very high clocked, very advanced 486. And extremely low power. Under typical load, the CPU core should consume around 100mW. By comparison, the CPU in your laptop can require anywhere from 10 - 35W. Idle power is even lower.
Paired with this CPU is a
PowerVR MBX-Lite GPU core. This GPU, like the CPU, is
built on a 90nm process and is quite simple. The GPU does support hardware transform and lighting but it’s fully fixed function, think of it as a DirectX 6/7 class GPU (Riva TNT2/GeForce 256).The MBX-Lite in the iPhone shares the same architecture as the MBX but is optimized, once more, for power efficiency and thus is significantly slower.
I don’t have exact clock speed information for the MBX-Lite in the iPhone but
I’m guessing around 60MHz.
Coupled with the CPU and the GPU in the iPhone’s SoC is
128MB of DDR memory, all on the same chip. It’s a pretty impressive little package. You get a CPU, GPU and memory all in a package that’s physically smaller than Intel’s Atom.
Now the 486 came out in 1989 and the original 3dfx Voodoo graphics card came out in 1996. The iPhone’s SoC would be ridiculously powerful if it were running the sorts of applications we had back then, but it’s not. We’re asking a lot from this little core and although it has performed admirably thanks to some clever software engineering on Apple’s part, it’s time for an update.
Although unannounced, the iPhone
3GS uses (again) a Samsung SoC but this time i
nstead of the ARM11 + MBX-Lite combo it’s got a Cortex A8 and PowerVR SGX; just like the Pre. The A8 lengthens the integer pipeline to
13 stages,
enabling its 600MHz clock speed (what I’m hearing the 3GS runs at). The Cortex A8 also widens the processor; the chip is now a
two-issue in-order core, capable of fetching, decoding and executing two RISC instructions in parallel.
The ARM11 processor in the iPhone/iPhone 3G has a basic vector floating point unit,
but the A8 adds a much more advanced SIMD engine called NEON. The A8 also has twice as many double precision FP registers as the ARM11. The addition of NEON and the improved vector FPU in the A8 makes the processor much less like the original Pentium and much more like Intel’s Atom. Granted, Atom is significantly faster than the A8, but it also draws much more power.
Caches also get a significant improvement. I believe Apple will be using a derivative of Samsung’s S5PC100, which has a 32KB/32KB L1 cache (I/D, we may see a 16KB/16KB config instead) and a 256KB L2 cache.
The L2 cache, as you’ll remember from the first section, is a new addition to the A8; the ARM11 core didn’t have an L2.
______________________iPhone 3G (ARM11)______iPhone 3GS (ARM Cortex A8)
Manufacturing Process____90nm_________________65nm
Architecture____________In-Order_______________In-Order
Issue Width_____________1-issue________________2-issue
Pipeline Depth___________8-stage_______________13-stage
Clock Speed_____________412MHz_______________600MHz
L1 Cache Size___________16KB I-Cache + 16KB D-Cache_32KB I-Cache + 32KB D-Cache
L2 Cache Size___________N/A___________________256KB
The combination of
higher clock speeds, more cache and a dual-issue front end results in a much faster processor. Apple claims
the real world performance of the iPhone 3GS can be up to 2x faster than the iPhone 3G, and I believe that’s quite feasible.
The new SoC is built on a
65nm manufacturing process, down from 90nm in the original hardware. However, power consumption should still be higher for the new SoC compared to the old one. ARM’s own site lists ~0.25mW per MHz for the ARM11 core but < 0.59mW per MHz for the A8. That’s for a 650MHz low power A8 core and I’m expecting 600MHz for the 3GS, that’s at most 3x the power consumption of the CPU in the original iPhone. So how can Apple promise better battery life?
The MBX-Lite used in the original iPhone was also a tile based architecture, the SGX is just better
Pixel, vertex and geometry instructions are executed by a
programmable shader engine, which Imagination calls its Universal Scalable Shader Engine (USSE). The “coprocessor” hardware at the end of the pipeline is most likely fixed-function or scalar hardware that’s aids the engine.
The SGX ranges from the PowerVR SGX 520 which only has one USSE pipe to the high end SGX 543MP16 which has 64 USSE2 pipes (4 USSE2 pipes per core x 16 cores). The iPhone 3GS, I believe, uses the 520 - the lowest end of the new product offering.
A single USSE pipe can execute, in a single clock, a two-component vector operation or a 2 or 4-way SIMD operation for scalars. The USSE2 pipes are upgraded that handle single clock 3 or 4 component vector operations, have wider SIMD and can co-issue vector and scalar ops. The USSE2 pipes are definitely heavier and have some added benefits for OpenCL. For the 3GS, all we have to worry about is the single USSE configuration.
(
http://www.anandtech.com)
"