MIPS32 Release 1

I think I've found a problem with the ALU inputs. See this small code snippet below:

104: 8fc20000 lw v0,0(s8) #reads value 0x00000000 into $v0 108: 8fc30010 lw v1,16(s8)#reads value 0x00000130 into $v1 10c: 00621021 addu v0,v1,v0 #should get 0x00000130 result in $v0, but actually get 0x00000260

It seems that the alu is doing 0x00000130+0x00000130 instead of 0x00000000+0x00000130. I guess it's something to do with the register write-back due to the fetch at PC 0x108 interfering with the ALU inputs?

Jeff

Hi Jeff,

I ran the same instruction sequence and $v0 received the correct value of 0x130.

Will you verify that your issue is reproducible? If it is, then please post a minimal instruction sequence that will produce the issue from a full reset, or at least the preceding five instructions of this sequence. Thanks!

-Grant