🚀 go-pugleaf

James Macleod (jmacleod@Direct.CA) wrote:
: In article <424t31$hhs@vixen.cso.uiuc.edu>, rsjohnso@ux6.cso.uiuc.edu (johnson r scott) says:
: ickDraw 3D, OpenDoc, and WorldScript...


: >
: >>Presumably there will be a major problem with porting the
: >>memory protection onto any 680x0 without an MMU -- that's
: >>all 68000s and 68020s, and quite a lot of 030s and 040s.
: >
: >No, you've got that wrong.  68020s, 68030s and 68040 all have

: I am not so sure. 

: There is an EC designation in the 68000 series that denotes a CPU
: with no MMU.

: I think these may have been used in some Macs, but I am not sure.

: I saw them used on some cheaper Amiga accelerators, and I think
: the Amiga 1200 used a 68EC020 with no MMU.

MMU is available as a separate chip (MC68851) for the MC68020 and built-in
since the MC68030. (the 1200 doesn't have MMU)

Actually EC has different meanings for each chip:

a)   MC68EC000 is a MC68000 with selectable 8 or 16 bit data bus and A0.
b)   MC68EC020 is a MC68020 with a 24 bit address bus rather than 32 bits.
c)   MC68EC030 is a MC68030 without a paged memory manager (PMMU).
d)   MC68LC040 is a MC68040 without a built-in math coprocessor (FPU).
e)   MC68EC040 is a MC68040 without a memory manager or built-in FPU.
f)   MC68LC060 is a MC68060 without a built-in math coprocessor (FPU)
g)   MC68EC060 is a MC68060 without a memory manager or built-in FPU.

(source: FAQ comp.sys.m68k)

: :)