64-bit / 128-bit data element type for array?

akineko akineko at gmail.com
Mon Dec 22 23:33:17 CET 2008


Hello Robert,

> Is that actually a 2s-complement 128-bit unsigned integer, or is it just a
> 128-bit-long chunk of data?

That is a good question.
A 128-bit data can be anything.
A 128-bit data can be an instrution code (VLIW machines use such wide
instruction). A 128-bit can be a packed ascill (16 chrs).
A 128-bit can be a descriptor (a structure of various fields).
It is probably safe to say that only unsigned 128-bit is required.
(I cannot think of any situations where signed 128-bit is necessary)

Hope this answers your question.

Aki Niimura

On Dec 22, 1:22 pm, Robert Kern <robert.k... at gmail.com> wrote:
> akineko wrote:
> > Hello,
>
> > bearophile and  Robert, thank you for your prompt response.
> > I will try NumPy (this is a good execuse to learn and to use a new
> > package).
>
> >> I haven't seen uint128 in the wild, though.
>
> > Of course, not many applications require uinit128 as a scalar value.
> > I may need to deal with 128-bit data as it is now not uncommon to have
> > 128-bit data bus (or even 256-bit wide and beyond) in ASICs
> > (microchip) design. Unfortunately, some designs use big-endian and
> > others use little-endian ...
>
> Is that actually a 2s-complement 128-bit unsigned integer, or is it just a
> 128-bit-long chunk of data?
>
> --
> Robert Kern
>
> "I have come to believe that the whole world is an enigma, a harmless enigma
>   that is made terrible by our own mad attempt to interpret it as though it had
>   an underlying truth."
>    -- Umberto Eco




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