Hi All, I'm making good progress on 64-bit Spur in the Stack VM simulator. But I've just noticed an image-level issue which could be indicative of lots of 32-bit assumptions baked into the Squeal/Pharo/Newspeak systems. SmallInteger>>digitAt: n "Answer the value of an indexable field in the receiver. LargePositiveInteger uses bytes of base two number, and each is a 'digit' base 256. Fail if the argument (the index) is not an Integer or is out of bounds." n>4 ifTrue: [^ 0]. self < 0 ifTrue: [self = SmallInteger minVal ifTrue: ["Can't negate minVal -- treat specially" ^ #(0 0 0 64) at: n]. ^ ((0-self) bitShift: (1-n)*8) bitAnd: 16rFF] ifFalse: [^ (self bitShift: (1-n)*8) bitAnd: 16rFF] This assumes that SmallInteger is only ever 4 bytes, which is unacceptably wasteful for my approach to 64-bits. In 64-bit Spur, SmallIntegers are 61-bit 2's complement. I'm raising this example at this point to see if the community might find similar issues and bring them to my attention. -- best, Eliot