Re: NASM 0.98.39 vs. NASM 2.03.01 disassembly
- From: Chuck Crayne <ccrayne@xxxxxxxxxx>
- Date: Thu, 4 Sep 2008 16:47:39 -0700
On Thu, 4 Sep 2008 10:39:10 -0400
"Rod Pemberton" <do_not_have@xxxxxxxxxxxxx> wrote:
"load" to me means a "read" of default register size.
The reason that one should not take such words too literally is that
they were chosen by a tech writer who was trying to explain a hardware
process in terms that an average programmer would understand.
From a hardware design point of view, "load" is acceptable in the case
where the selector must be fetched from memory, but is inappropriate
when the selector has already been loaded into a register. Every bit the
cpu logic needs to access can be accessed directly from the source
register, so gating it to some hidden 32-bit register would merely
waste cpu resources.
Nor does the concept of "default register size" apply to the source
register. The cpu uses bits 0-2 to enforce the security rules; bit 3
to select between the GDT and LDT; and bits 4-15 as an index into the
selected table. Under no circumstances does it deal with 8, 16, 32, or
64 bit entities.
--
Chuck
http://www.pacificsites.com/~ccrayne/charles.html
.
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