RE: [fpu] Architecture

[Sagheer.Ahmad@infineon.com]

-----
>do you mean that FPU has to decode all instructions? and so all exe units?

>I assume that the FPU and cpu will act synchronosly and there will be no handshake
>which is suitable for pipelines and morework on the datapath controller.

>do you suggest a micro sequencer for the FPU control? that will carry all fpu
>operations and be connected to the cpu datapath?


>Jamil Khatib

No, FPU does't neet to decode all instructions ... to go into implementation
details, CPU will inform the FPU (along with opcode) whether instruction is
meant for FPU or not (for example: from core we will have a signal 'fpu_valid').
So in the same clock (when FPU receives opcode) FPU will also receive fpu_valid...

As I said, in the previous email, FPU can raise a signal (say; 'sigle_cycle') in
the same cycle or in the subsequent cycles (if multicycle......say 'multi_cycle').....

So what issue unit (other cpu datapath) need to take care is.....do not issue inst
to its units until FPU is finished (if FPU inst is single cycle...issue unit can
continue in the same cycle based on single_cycle signal....other wait for multi_cycle signal). 
Also cpu has to provide (operands) and collect result from FPU.

Sagheer Ahmad. 


__________________________________________________
Do You Yahoo!?
Talk to your friends online with Yahoo! Messenger.
http://im.yahoo.com