🚀 go-pugleaf

In article <880@taniwha.UUCP> paul@taniwha.UUCP (Paul Campbell) writes:

| In article <14900025@hpdmd48.boi.hp.com> sritacco@hpdmd48.boi.hp.com (Steve Ritacco) writes:
| >From what I know about the R3000, the only integer unit instruction affected
| >by 64-bit operation would be the shift instructions which only have a 5 bit
| >field for shift amount.  Clearly you would have to use the register varient
| >of the shift instructions, but other than that all the instructions would work
| >for 32 or 64 bit opperands.  I'm under the impression that the instruction
| >set was layed out for minimal affect on word size.
| 
| What about add/sub instructions - they trap on overflow, also any compare
| instruction that tests the sign bit - one solution for this might be
| for the 32-bit instructions to use the high 32-bits of a register
| (you would need new load/store instructions), or you could have a 
| 64-bit/32-bit flag that puts the CPU into a particular mode (hopefully
| there would be one each for user/supervisor modes)

The other thing I've thought about is how do you do generalized
external references.  On the current R[236]000's a normal (non-GP)
reference is two instructions:

	lui	$at,addr>>16
	<lw/sw>	<reg>,addr&0xffff($at)

I wonder whether we will need four instructions in the 64 bit
universe.
--
Michael Meissner	email: meissner@osf.org		phone: 617-621-8861
Open Software Foundation, 11 Cambridge Center, Cambridge, MA, 02142

You are in a twisty little passage of standards, all conflicting.