IEEE double extended format <9302012100.AA02479acsa.nsa.hp.com>

[Omar G. Stradella]

Your message dated: Mon, 01 Feb 93 13:00:50 PST

>> 2)  Do you know of any manufacturer that is going a different direction, 
>>     and if so, why?
>
>Need to check on IBM's "doubled" format used in the RS/6000.  Perhaps
>someone at IBM could comment on how its defined and used.  I'm not
>sure if its a "double extended" format or only a > 64-bit format.

IBM's "doubled" format in the RISC System/6000 is not architecturally 
defined. It is implemented as two 64-bit real numbers and the operations 
are handled using libraries. The format is:

Bit no. 0....|....1....|....2....|....3....|....4....|....5....|....6...
        seeeeeeeeeeeffffffffffffffffffffffffffffffffffffffffffffffffffff
Bit no. .|....7....|....8....|....9....|....0....|....1....|....2....|..
        seeeeeeeeeeeffffffffffffffffffffffffffffffffffffffffffffffffffff

Thus, there are only 104 bits for the fraction and the precision is clearly
lower.


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