PowerPC vs PowerPC : A Comparison Of The G3 and G4 Processors
Below you will find a features comparison between the current
G3 processor and the G4 which is now being used in the current PowerMac
G4 computers form Apple. We have also included some benchmarks
comparing the two chips. The benchmark used to test the chip's performance
does not utilize the "Velocity Engine"(AltiVec)
of the G4. So the chip's integer performances are basically the same
at similar clock speeds. At the moment there is not much software out
there that takes advantage of the "Velocity Engine." Hopefully
in the coming year this will change dramatically and we will see the
G4 cleaning the G3's clock. Benchmarking programs such as SPEC95
and MacBench will have to be updated
to reflect the true potential of the G4 chip. It is still interesting
to note the G4's significantly improved floating point performance which
should be welcomed in the scientific and graphics fields.
| PowerPC Chip Features Comparison | ||
| Specs | PowerPC G3 (750) | PowerPC G4 (7400) |
| CPU Bus Dividers | 3X, 3.5X, 4X, 4.5X, 5X, 5.5X, 6X,6.5X, 7X, 7.5X, 8X, and 10x | x3, x3.5, x4, x4.5, x5, x5.5, x6, x6.5, x7, x7.5, x8, x9 |
| Bus Interface | 64-bit data 32-bit address |
64-bit |
| Instructions Per Clock | 3 (2+branch) | 3 (2+branch) |
| L1 Cache | 32K Instruction 32K Data |
32K Instruction |
| Backside L2 Cache Support | Supports 256 KB, 512 KB or 1 MB | 512K, 1MB or 2MB |
| Core-to-L2 Frequency Divisions | 1:1, 1.5:1, 2:1 2.5:1, 3:1 | 1:1,1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1 |
| Typical/Max Power Dissipation | 4.7W @ 400 MHz | 5.0W/11.5W @ 400 MHz |
| Die Size | 40 sq mm | 83 sq mm |
| Transistors | 6.35 million | 6.5 million |
Processor Performance Comparisons -SPEC 95
Below you will find processor comparisons for PowerPC G4 and G3 chips that are based on the manufacturer's published results.
The results directly below were obtained by using the benchmarking program SPECint 95 which measure Integer intensive tasks
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The results below were obtained by using the benchmarking program SPECfp 95 which measures Floating Point intensive tasks
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Previous Processor comparisons. Your feedback on these results
Actual Scores
| Processor | SPECint95 | SPECfp95 |
| PowerPC G4 | 21.4 | 20.4 |
| PowerPC G3 | 21.4 | 13.8 |
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SPEC, the Standard Performance Evaluation Corporation, is a non-profit corporation formed to "establish, maintain and endorse a standardized set of relevant benchmarks that can be applied to the newest generation of high-performance computers" (quoted from SPEC's bylaws). The founders of this organization believe that the user community will benefit greatly from an objective series of applications-oriented tests, which can serve as common reference points and be considered during the evaluation process. While no one benchmark can fully characterize overall system performance, the results of a variety of realistic benchmarks can give valuable insight into expected real performance. SPEC is a non-profit corporation registered in California. SPEC basically performs two functions: SPEC develops suites of benchmarks intended to measure computer performance. These suites are packaged with source code and tools and are extensively tested for portability before release. They are available to the public for a fee covering development and administrative costs. By license agreement, SPEC members and customers agree to run and report results as specified in each benchmark suite's documentation. SPEC publishes news and benchmark results in The SPEC Newsletter and The GPC Quarterly. Both are available electronically through http://www.spec.org/ (and available in paper as a quarterly publication if necessary) this provides a centralized source of information for SPEC benchmark results. SPEC95 refers to the total SPEC95 product provided by SPEC. SPEC95 is composed of two suites of benchmarks: SPEC CINT95: a set of eight compute-intensive integer/non-floating point benchmarks SPEC CFP95: a set of 10 compute-intensive floating point benchmarks These are intended to provide a measure of compute-intensive performance of the processor, memory hierarchy and compiler components (the 'C' in CINT95 and CFP95) of a computer system for comparison purposes. For Free Macintosh Hardware - Click Here |
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