I don't know about the specifics of Doom 3's developer decisions but I know that when it comes to CPUs, performance has really skyrocketed.
A low-end desktop Sandy-Bridge i3 CPU running a single-threaded task on one core is almost 5 times faster than a Venice Athlon 64 singlecore that was released in 2005 if memory serves right. When you factor in the second core and HyperThreading (if it helps the workload) it wouldn't be unreasonable to claim that performance has increased by an order of magnitude or more.
On the other hand, memory speed (both latency and bandwidth) hasn't changed much in that timeframe. That means that relative to the speed of the CPU, it takes much longer to access memory now than a decade ago, and so stuff that made sense to cache in memory back then will probably be faster to recompute whenever needed nowadays instead.
Maximum theoretical bandwidth may not have increased at the same pace but modern memory controllers are a lot more efficient. I'd wager that the CPUs are kept adequately fed even without extremely fast RAM like on GPUs.
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I don't know about the specifics of Doom 3's developer decisions but I know that when it comes to CPUs, performance has really skyrocketed.
A low-end desktop Sandy-Bridge i3 CPU running a single-threaded task on one core is almost 5 times faster than a Venice Athlon 64 singlecore that was released in 2005 if memory serves right. When you factor in the second core and HyperThreading (if it helps the workload) it wouldn't be unreasonable to claim that performance has increased by an order of magnitude or more.
On the other hand, memory speed (both latency and bandwidth) hasn't changed much in that timeframe. That means that relative to the speed of the CPU, it takes much longer to access memory now than a decade ago, and so stuff that made sense to cache in memory back then will probably be faster to recompute whenever needed nowadays instead.
Maximum theoretical bandwidth may not have increased at the same pace but modern memory controllers are a lot more efficient. I'd wager that the CPUs are kept adequately fed even without extremely fast RAM like on GPUs.