Thanks Chuck. That was the piece I was forgetting to actually say.
Tony Thigpen
Chuck Arney wrote on 11/04/2014 09:25 PM:
A 64-bit address is only ambiguous when the high word is zero and the high bit
of the low word is on. When the high word is non-zero all 32 bits of the low
word can address storage locations without ambiguity.
Chuck Arney
Arney Computer System
On Nov 4, 2014, at 6:22 PM, Paul Gilmartin
<[email protected]> wrote:
On 2014-11-04, at 17:07, Tony Thigpen wrote:
The first bit of the address in the PSW indicates that the address is a 31 bit
address. So, there was ambiguity for any address with the first bit set on.
Was the bit on because it was 31bit code setting the flag, or was it a real
address in 64bit mode?
It was easier to just block out the range as unusable.
Wouldn't that be similarly true for ranges such as 6GiB <= A < 8GiB,
10 GiB <= A < 12 GiB, ...? Are all such ranges blocked out?
-- gil
