Need explanation of the CPU and FPU technology on turbo boards

[Piru]

@Hyperspeed

Archiving tools certainly do not use FPU, at least not for anything time critical such as compression or decompression.

[Piru]

iirc divide was the only 16bit math instuction the 68000 had (16bit divided by 16bit resulting in 32bit answer).

Actually divu/divs was 32bit / 16bit -> 16r:16q, with 'V' flag set if the result would overflow 16bit.

[Piru]

To recap: FPU isn't really required for most things. If you really must run some scientific precision math things, or say for example render high precision mandelbrots or 3D scenes, you might want one. Then again, with these applications you're better off with 68060 and integrated FPU anyway. ;-)

[Piru]

several people have said that there is a prog which has an fpu version which is slower and hinted at why, please tell us why it is slower i dont have the docs

Original mpega.library has FPU version that is considerably slower than the integer one. It supposedly has better quality (but frankly, you can't hear the difference). It's slower because the floating point algorithm is quite different from the integer one.

[Piru]

@Vulture

Which one of those listed apps require FPU to function at all?

[Piru]

does it have a oscillator or is it oscillated by the motherboards own clock?

It uses the motherboard clock (~28MHz/2), so it's difficult (but probably not impossible) to overclock. You could possibly use external clock to drive the CPU, but I've never seen such hack myself (also: would it cause problems with the CPU accessing the system bus?).

Overclocking the motherboard clock is out of the question as it will skew all chipset timing.

[Piru]

Overclocking the FPU will have very little effect at all. It certainly won't make any difference in Workbench. Heavy FPU number crunching should speed up, say rendering some 3d scene or calculating mandelbrots etc.

In my experience FPU doesn't overclock very well, it'll easily begin to generate errors (this was with 33MHz chip at 50MHz).

[Piru]

This was 68882 on Blizzard 1230-III.

Well, I guess I was just unlucky.

[Piru]

Overclocking the motherboard clock is out of the question as it will skew all chipset timing.