transfer from real to logical
in [Fortran]
|
From: robin on 9 Dec 2009 19:34 "glen herrmannsfeldt" <gah(a)ugcs.caltech.edu> wrote in message news:hfmgdq$mov$1(a)naig.caltech.edu... | Ken Fairfield <ken.fairfield(a)gmail.com> wrote: | (snip) | | > VAX does not support any IEEE formats, although G_float is very | > similar to IEEE double precision. | | > OTOH, Alphas have two different single precisions floating point | > formats: F_float, the native VAX version, and S_float, | > the IEEE version. | | As I remember it, Alpha has load/store instructions that | support different formats, but there is only one format | for each width in the registers, which I believe is IEEE. | In some cases, a few low bits of the significand will be lost | on load or store. Also, overflow or underflow might occur. | | > For double precision (64-bit) there are | > two VAX double precision formats, D_float and G_float, and | > the IEEE version, T_float (three altogether). | | > VAX also had | > a 128-bit, extended precision float sort of optionally | > available (I think it was a hardware add-in, but possibly | > supported in software without the hardware) called H_float. | > Seems that Alpha supports only the IEEE X_float for 128 bit | > reals. | | H float was standard on the 11/730, at least. For some of | the others it was optional (microcode), but supported by | software emulation if not hardware. F_floating was available for single precision, and D_floating for double precision. Both used an 8-bit exponent and were therefore compatible. G_floating was for double precision, and used an 11-bit exoponent. H_floating (quad precision) used a 15-bit exponent.
From: glen herrmannsfeldt on 9 Dec 2009 21:47 robin <robin_v(a)bigpond.com> wrote: > The mantissa sign could be anywhere, but it usually is at the left, > in order that a simple hardware instruction can inspect it > (in point of fact, typically the same hardware or microcode that inspects > the sign of an integer). And of course it isn't for VAX... -- glen
From: Frank on 9 Dec 2009 23:00 On Thu, 10 Dec 2009 02:47:14 +0000 (UTC), glen herrmannsfeldt wrote: > robin <robin_v(a)bigpond.com> wrote: > >> The mantissa sign could be anywhere, but it usually is at the left, >> in order that a simple hardware instruction can inspect it >> (in point of fact, typically the same hardware or microcode that inspects >> the sign of an integer). > > And of course it isn't for VAX... > > -- glen Does VAX exist as a computing counter-example? Why do smart people like you keep talking about them? -- frank
From: glen herrmannsfeldt on 10 Dec 2009 00:30 Frank <frank(a)example.invalid> wrote: (snip, I wrote) >> And of course it isn't for VAX... > Does VAX exist as a computing counter-example? Why do smart > people like you keep talking about them? The computers still exist and still run. Most of the earlier ones aren't running, though might be in museums. The MicroVAX are small enough to still run. Otherwise, an architecture exists even if no implementations of it still exist. -- glen
From: Frank on 10 Dec 2009 04:41
On Thu, 10 Dec 2009 05:30:38 +0000 (UTC), glen herrmannsfeldt wrote: > Frank <frank(a)example.invalid> wrote: > (snip, I wrote) > >>> And of course it isn't for VAX... > >> Does VAX exist as a computing counter-example? Why do smart >> people like you keep talking about them? > > The computers still exist and still run. Most of the earlier ones > aren't running, though might be in museums. The MicroVAX are small > enough to still run. Glen, you're an international asset. I loved the pac-10 this season. Were you for the ducks this time? > > Otherwise, an architecture exists even if no implementations > of it still exist. > > -- glen Merry x-mas, wall-e. |