Re: Doom Conversion (was Dragons Lair

[Leslie M. Barstow III <wdphoenix@delphi.com>]

Joseph <jlee@clyde.ICS.UCI.EDU> writes:
 
>Now where are you getting this info from? Where's the benchmarks?  A 486
>can execute most of its instructions in around 1 cpu cycle.  With a
 
Here's my basis...
A GS's average cycle count is about 3-4.
A Mac's average cycle count (excluding the PowerPC) is about 8
A 386 (relative to a Mac) uses about 3 times more average.
The 486 reduced this by half.
Therefore, a GS should run things about 3 times faster than a 486 of equivalent
speed, if both are optimized equally.
The GS-Mac, Mac-386, GS-386, and 386-486 comparisons are all out there...
 
I don't know where you get your information - the 486 is not a pipelining
chip.  It is impossible to do anything in one cycle without some advanced help.
The best the 486 can do (assuming intelligent cacheing) is about 3-4 cycles,
assuming it accesses some information other than the instruction.
 
For comparison, take the GS adc instruction:
cycle   operation
1       load instruction
2       load immediate data
3       A + M -> A (c)
 
This is typical of a simple instruction.  It is also NOT typical of most x86
instructions, which require additional processing to determine addressing mode,
length of instruction, etc.
 
Although Dhrystone exists for the GS, I am unsure if it is optimized, and I
guarantee all x86 versions are quite well-optimized.  Benchmarks would be
somewhat lopsided considering this - we're not measuring compilers, we're
comparing chips.
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