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Information about the Apollo CPU and FPU.

FPU Precision On V4SA?

Christian Z

Posts 13
13 Feb 2021 11:01


Excuse me for asking a probably dumb question. What is the precision of the FPU currently (i.e., with Build 7905 RELEASE5) available on the V4SA?

I know from https://wiki.apollo-accelerators.com/doku.php/apollo_core:fpu that you omitted support for Motorola's proprietary 80-bit extended precision, which is completely understandable. But does the FPU on the V4SA make use of all *64* bits of double precision floating point numbers?


Gerardo González-Trejo

Posts 53
14 Feb 2021 03:23


I think it was 64 bits, at least months ago. That information may already be out of date with latest updates.


Gunnar von Boehn
(Apollo Team Member)
Posts 5294
14 Feb 2021 06:15


Christian Z wrote:

Excuse me for asking a probably dumb question. What is the precision of the FPU currently (i.e., with Build 7905 RELEASE5) available on the V4SA?

 
R5 release supports 56 Bit FPU precision.
The upcoming R6 release support 64 bit.


Rollef 2000

Posts 21
14 Feb 2021 11:20


Christian Z wrote:

  Motorola's proprietary 80-bit extended precision

no, it is part of IEEE754


Christian Z

Posts 13
14 Feb 2021 12:46


Gunnar von Boehn wrote:

  R5 release supports 56 Bit FPU precision.
  The upcoming R6 release support 64 bit.

Thank you for clarifying this! I was trying some numerical benchmarks that check themselves (to see if they're really being run in double precision) and I was already suspecting a bug in the compiler.

Looking forward to R6, then.

posts 5