26 May
2016
26 May
'16
4:20 p.m.
On 24 May 2016 at 23:10, Fred Cisin <cisin at xenosoft.com> wrote:
Whether 8088 was an "8 bit" or "16
bit" processor depends heavily on how you
define those.
Or, you could phrase it, that the 8 bit processors at the time handled 64KiB
of RAM.
OK, thank you all for the responses.
Rarely have I felt so lectured and indeed talked-down-to in CCmp. :-D
No, it's a fair cop, I egregiously over-simplified my comment.
So let me try to address (haha) that.
Most 8-bit CPUs that I knew of had a 16-bit address bus, and thus were
limited to 64kB of physical memory (excluding bank switching &c.)
Most 16-bit CPUs I knew of (ignoring issues of internal ALU width
etc.) had 24-bit address buses and could thus handle 16MB of physical
memory. This includes cut-down internally-32-bit-wide devices such as
the 80386SX and 68000.
The 8088/8086 had a 20-bit address bus, differing mainly in the width
of the *data* bus, and the later 80286 had a 16-bit address bus.
So, yes, generally, 8-bitters could handle 64kB but 16-bitters 16MB.
As far as memory *size* considerations go, the width of the data bus,
multiplexing or multicycle accesses etc. are not germane to the
quantity of addressable memory.
So I was broadly right that the 8088/8086 sit somewhere on the
dividing line? That at least is good to know!
--
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