FSB Higher than 400 MHz
We saw telltale signs of memory controller tweaks and perhaps others with Sciencemark Membench, but our SuperPi 8M results seem to show that performance wise, the P35 is no faster than its older sibling, P965. The only new 'wrinkle' it has for the 1333 MHz processor is the (re)introduction of asynchronous memory support - which is not all that great anyway. We still saw that synchronous memory settings is still the way to go with Intel chipsets (memory controller). Is this all there is to it? Well, not quite. The major concern with P965, especially for overclockers is its well known FSB limitation. The P965 was clearly not designed to go far beyond 400 MHz. From what we saw in our article concerning the matter, we think the P965 chipset simply couldn't 'loosen' internal chipset timings to handle FSBs higher than 400 MHz. One of the key features Intel promised overclockers everywhere with P35 (and X38) is no more FSB limits.Let's see if this is true. Unfortunately, we only managed to top off at 466 MHz with this setup. Higher FSBs are definitely possible on the P35, but we lack the necessary processor cooling, so we'll have to settle for 466 MHz or 1864 MHz effective according to Intel's FSB mantra. We used TeamExtreme DDR2 1200 MHz 1 GB memory modules for this test, rated at 5-5-5-15 at 1200 MHz with 2.35 - 2.45 volts. Since 6 x 466 MHz still equals to 2.8 GHz, we kept the processor's voltage, but raised FSB, MCH and PCI-E voltage until the setup was stable (enough for our preliminary tests).
Core 2 Duo E6550 & P965
| 6x400 MHz | 7x400 MHz | 6x466 MHz | |
| Bandwidth | 5849.68 MB/s | 6299.01 MB/s | 6594.95 MB/s |
| Latency | |||
| 4 byte stride | 3 cycles | 3 cycles | 3 cycles |
| 16 byte stride | 9 | 9 | 11 |
| 64 byte stride | 36 | 35 | 38 |
| 256 byte stride | 132 | 127 | 141 |
| 512 byte stride | 150 | 146 | 157 |
Core 2 Duo E6550 & P35 - DDR2
| 6x400 MHz | 7x400 MHz | 6x466 MHz | |
| Bandwidth | 5986.77 MB/s | 6324.57 MB/s | 6835.86 MB/s |
| Latency | |||
| 4 byte stride | 3 cycles | 3 cycles | 3 cycles |
| 16 byte stride | 10 | 9 | 10 |
| 64 byte stride | 42 | 35 | 40 |
| 256 byte stride | 129 | 124 | 129 |
| 512 byte stride | 144 | 139 | 150 |
In addition to overall better stability at this FSB, the P35 also offer higher bandwidth than the P965. Interestingly, latencies are lower - 129 cycles to 141 cycles for 256 byte stride and 150 cycles to 157 cycles on the P965. How does it perform on SuperPi 8M? Let's find out.
Core 2 Duo E6550 & P965
| 6x400 MHz | 7x400 MHz | 6x466 MHz | |
| Iterations | seconds | seconds | seconds |
| 1 | 13 | 11 | 11 |
| 2 | 24 | 21 | 21 |
| 3 | 36 | 31 | 30 |
| 4 | 47 | 41 | 40 |
| 5 | 58 | 51 | 50 |
| 6 | 70 | 61 | 60 |
| 7 | 81 | 71 | 70 |
| 8 | 93 | 81 | 80 |
| 9 | 104 | 91 | 90 |
| 10 | 115 | 101 | 100 |
| 11 | 127 | 111 | 110 |
| 12 | 138 | 121 | 119 |
| 13 | 149 | 131 | 129 |
| 14 | 161 | 141 | 139 |
| 15 | 174 | 151 | 149 |
| 16 | 183 | 161 | 159 |
| 17 | 195 | 171 | 169 |
| 18 | 206 | 181 | 179 |
| 19 | 217 | 191 | 189 |
| 20 | 228 | 201 | 198 |
| 21 | 239 | 210 | 208 |
| 22 | 249 | 219 | 216 |
Core 2 Duo E6550 & P35 - DDR2
| 6x400 MHz | 7x400 MHz | 6x466 MHz | |
| Iterations | seconds | seconds | seconds |
| 1 | 12 | 11 | 11 |
| 2 | 23 | 21 | 20 |
| 3 | 35 | 31 | 30 |
| 4 | 46 | 41 | 40 |
| 5 | 57 | 51 | 50 |
| 6 | 68 | 61 | 60 |
| 7 | 79 | 72 | 70 |
| 8 | 91 | 82 | 79 |
| 9 | 102 | 92 | 89 |
| 10 | 113 | 102 | 99 |
| 11 | 124 | 112 | 109 |
| 12 | 138 | 122 | 119 |
| 13 | 147 | 132 | 129 |
| 14 | 158 | 142 | 139 |
| 15 | 169 | 152 | 149 |
| 16 | 180 | 163 | 158 |
| 17 | 191 | 173 | 168 |
| 18 | 202 | 183 | 178 |
| 19 | 213 | 193 | 188 |
| 20 | 224 | 202 | 197 |
| 21 | 235 | 212 | 207 |
| 22 | 245 | 221 | 215 |
At 466 MHz FSB, the additional bandwidth on the P35 allows it to finish SuperPi 8M calculation faster by 1 second. Well, P35 does offer more performance on higher FSBs and there's likely more frequency headroom if you're lucky or brave enough. That's good news for overclockers dissatisfied with P965 FSB wall.
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