it seem to me that modern compilers generate only xmm (ymm?) 16 register code and thus classic fpu commands gone out.. i am not sure tho this, this is just some observation.. is this true ? In modern compiled program there is no classic fpu at all? is xmm code noticably faster?

SSE is way better than x87(FPU). Every CPU from the last decade supports SSE, so some new compilers compile SSE by default.

BTW, AVX is better then SSE. This is true for AVX128 as well - AVX has non-destructive destination, so compilers can better utilize the xmm registers.

Assuming you're using Visual Studio:

- All 64 bit programs will use SSE instructions, because all 64-bit CPUs have them and x87 isn't supported in the ABI.

- 32 bit programs may still use the x87 FPU instructions, depending on the the /ARCH switch, which defaults to SSE2 from 2012 onwards.

The documentation also says the compiler can use x87 code in 32-bit programs where it's faster than the SSE alternative.

The most modern processor without SSE2 is the AMD Athlon XP, which is old enough that it should be safe to compile your game with /ARCH:SSE2. In fact these days almost everyone has SSE3 CPUs. Take a look at http://store.steampowered.com/hwsurvey?platform=pc#cat0 under "Other Settings (PC)".

fpu at all? is xmm code noticably faster?

Generally speaking, yes. Intel particularly has been dedicating on improving SSE2 latency & throughput while ignored x87 for quite a while by now.
This means that simple operations like multiplication and division can be faster when using xmm registers (on modern architectures, that is)

Probably the most noticeable difference is that C/C++ mandate to truncate floating point to integer conversions; which means when you do "int myInt = (int)(myFloat)"; the compiler has to insert a call to a function that will ensure the rounding mode is correct (and switching rounding modes can be expensive)

In SSE2, there is a function for truncated conversions, cvttss2si; which is inexpensive considering it doesn't involve switching rounding modes, nor checking them.

ye, i know well that shit,

as to fpu and sse the difference is noticable - afaik the

sse got no such command like fsin, fcos, log, pow etc,

what with that?

also does scalar sse work good on unaligned floats?

there is no stack in sse and maybe this is good because

really i do not know what this stack was good for..

also some sse got 8 xmm regiosters, some got 16 of

them and 16 is much better than 8 i think,

What is a criterium to say this cpu has 16 xmm? is this

a version number or this is 32bit/64bit difference?

also sse do not get long doubles (80 bit0 i liked to use them sometimes

also some sse got 8 xmm regiosters, some got 16 of

them and 16 is much better than 8 i think,

What is a criterium to say this cpu has 16 xmm? is this

a version number or this is 32bit/64bit difference?

32 bit is 8 registers, 64 bit is 16 registers, regardless of what CPU you have. Something to do with the register representation when encoding instructions and backward compatibility.