Chip ram?
Jim, please, don't use the term 'MS-DOS' around these parts, many find
it offensive. 8)
Seriously, that is an obvious question. The Amiga has NONE of the
problems which MS-DOS has regarding memory management. There is no
segmentation, no paging, no none of that.
Any data which must be referenced by the custom chip set (eg. graphics,
sound and disk buffers) must be placed in what is called 'chip ram'. The
chip ram is the only memory accessible by the custom chips. This memory is
accessed on alternate cycles by the custom chips and the CPU. This RAM is
therefore slower for non-chip set uses than is fast ram (thus the name fast
ram 8).
Currently all machines sold by dealers have 1MB of chip ram (1MB
agnus's), except for the A3000 which can have 2MB of chip ram. The A500C,
being sold by retailers like Macy's, has only 512K of chip ram. This memory
can, of course, also be used for non-chip related activities, such as
loading programs, but in general you want to use your fast-ram first.
This implies that you can get an out-of-memory error when you still have
megabytes left to spare. If a program needs to open a screen and you are
out of chip ram, even if you still have fast ram, you are out of luck.
On IBMs, there is a similar concept in that the video card will have ram
on it. The advantage is that the Amiga has a blitter which can do
high-speed manipulations on that ram and that the ram can be used for other
things as well.
The bus on the 500 and the 2000 line are 16 bits wide and 7.14MHz, a
speed related to the NTSC television standard. The 2500 has a separate bus
for high-speed 32 bit access to ram, although the chip ram must still be
accessed via the old bus. The A3000 is completely redesigned, except for
the chip set. There are now two buses: the old chip-set bus and everything
else. Chip ram is linked via both buses so that the 68030 doesn't have to
drop to the 16 bit bus to access the ram.
Finally, chip ram and fast ram are non-continuous. So, for example, if
[ MORE ]