Mill Computing, Inc. Forums The Mill Architecture Memory Reply To: Memory

imbecile
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Post count: 48

>The great majority of transfers are direct and don’t use pointers, and those have neither load nor belt positions. You can branch to a label or call a function in a single operation with no belt change. Color me confused.

That’s because I was confused due to lack of information and misinterpreting.

>Given a 64-bit address space, static linking is right out

True. Static linking should always be an offset to some implicit base too, especially in 64bit. Whether that base is NULL or some other fixed address or the current program counter for relative addressing doesn’t matter. The important part for static linking is that you can compute the final destinations at compile time and hardcode them into the instruction stream relative to that implicit base.

Now having read your reply I get the impression that there is an implicit base for each module a process uses that is handled somewhere else that is not a belt slot, and that those implicit bases likely are initialized at module load time in some separate mapping structure in parallel to the virtual addresses.

> there’s no advantage to fixing the base

I can actually think of a few advantages to fixing the base (which of course is only possible when you don’t have a SAS). But:

>The obvious one is getting the TLB out of 90+ % of memory access.

When this indeed means that in 90% of the memory accesses the virtual address is the physical address and a translation is unnecessary and not done, I fully agree that this would obliterate any advantage I have in mind. I just can’t imagine how this would be feasibly implemented, you would need to know whether an address needs translating before you actually bother to look it up. I guess this can done with the protection zones.

If that is not the case, and you still have to do address translation on every memory access, then I guess I could start listing and explaining all those advantages I figure fixed bases and offsets have to offer, especially on an architecture like the Mill.

  • This reply was modified 8 years, 4 months ago by  imbecile.