

Doom 3 BFG Technical Documentation - basil
http://fabiensanglard.net/doom3_documentation/index.php

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exDM69
A lot of the article is about memory bandwidth vs. cpu computation. In Doom 3
BFG, as opposed to the original release, a lot of things were recomputed
instead of stored in memory.

This begs the question, was it really faster to store that stuff (e.g. skinned
meshes, shadow volumes) back in 2004 when Doom3 came out? Has the hardware
really changed that much in the 8 or so years between the original and the BFG
releases? Or was this another case of premature optimization and doing things
the way they were always done before?

In addition to memory bandwidth vs. cpu throughput, the number of cores in
your average consumer cpu has gone up from 1-2 to 4 (or "8 cores" with
hyperthreading). Reading between the lines, this was a motivator for the
changes. Sharing memory between the cores is expensive and clearly some of the
changes were made in order to reduce sharing between the CPUs.

So if any of the Doom 3 coders are reading this, can you give some insight on
these changes? :)

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ferongr
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.

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Narishma
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.

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ferongr
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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erikpukinskis
When he mentioned Doom 3 coming out 10 years ago, I couldn't believe it.

But I looked, and holy crap: released 2004. I don't know why, but that makes
me feel particularly old.

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chii
at first i thought they had written an actual tech spec of the weapon BFG!

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IbJacked
Heh, me too. Now, after having read the entire technical note, I wish that was
the case.

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duskwuff
That document exists too:

[http://www.gamers.org/docs/FAQ/bfgfaq/](http://www.gamers.org/docs/FAQ/bfgfaq/)

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nolok
The background of that website reflects well the year it was written (1999).

