[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Implementor support for the binary interchange formats



IBM's System Z mainframes, and its S/390 predecessors since 1998, support
binary128 in hardware -- actual hardware, not millicode, except for a few
difficult instructions like divide-to-integer (IEEE exact remainder) and
(since Z9 in 2006) radix conversions, which are in millicode (IBM's term
for vertical microcode that uses a near-subset of regular instructions,
sort of like PALcode on Alpha).  In fact, 128-bit FP in IBM's hexadecimal
format (HFP, since S/360) has been available in hardware since 1976 (with
the exception of 128-bit divide, which came along 20 years later).

IBM's decimal128 is also supported in hardware on those machines that have
hardware DFP, starting in 2008 with the Z10 and the Power6.  The Z9 had
DFP in millicode (with special assist hardware for DPD encode/decode and
BCD arithmetic, exploiting the old packed-decimal arithmetic of S/360
vintage).  A millicoded instruction looks the same as hardware from the
ISA point of view, i.e. it does not require extra software from either
operating system or runtime libraries.

Michel.

P.S.  The dates above are as I recall them; you need to refer
      to announcement letter archives to get official dates.
---Sent: 2011-03-01 13:40:04 UTC


754 | revision | FAQ | references | list archive