| I think it was Dave Haynie or George Robbins of CBM who said that
they were thinking of putting the color composite back into the
A500 on a future run. Apparently lots of people want it, and don't
want to have to pay for a Genlock to get it. (Gee, I'm not even
sure that a Genlock will do it).
The reason that they left the chroma signal out is that a lumna
only signal looks much better on a cheap monochrome monitor. I
think they wanted to be able to say that the A500 also has a monochrome
hookup, to counter Atari's monochrome. The Atari ST monochrome
display is light years ahead of anything you'll ever get out of
any composite signal.
Speaking of composite video, Amazing Computing has a good article on
how to improve the composite output of an A1000. Apparently, CBM used an
incorrect impedence load on some standard chip. As a result, the
composite signal is way too hot. It can be fixed by snipping a single
resistor. They used the same chip correctly on the A500.
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re: .0 Fat Agnus
It's my understanding that the A500 Agnus has sufficient pinouts
to handle 2-Meg, but it is not yet capable of doing so. I would
take this as an indication that sometime in the future the A500
might come with the real Fat-Agnus. This could be a major advantage
of the A500 over the A1000, but it hasn't happened yet...
regards,
steve mcafee
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| Re: .0
The fat Agnus found in the Amiga 500 and the second production run
(the Westchester design) of the Amiga 2000 has pins only to address
one meg of memory. (The first production run of the Amiga 2000, the
German design, used the Amiga 1000 Agnus. That Amiga 2000 only had
a half meg on the mother board. The other half meg was on another
board that plugs into the processor slot.)
The one meg of memory that is standard on the Westchester Amiga 2000
and the Amiga 500 (well, standard after the .5 meg upgrade) is in the
address space reserved for chip memory in the Amiga architecture.
However, that version of the fat Agnus chip can only use one half meg
as chip memory. The other half meg is typed as "fast memory," even
though it does suffer from cycle stealing just like chip memory.
The rumors are that a future update to the Amiga 500 and Amiga 2000
Agnus will allow the entire one meg as chip memory. (The 68000 and
the custom Amiga chips are socketed for easy replacement.)
How much does the slow fast ram slow down the system? I would suspect
not much at all. Cycle stealing doesn't happen much in practice. Most
programs don't use high res, interlaced, 16 color displays: that's a bit
of overkill for a spreadsheet or word processor.
Also, the Amiga memory manager supports memory priorities. One of the
new programs that comes with the Amiga 500 is one that marks the so
called "half-fast ram" to be allocated only after all the standard fast
ram has been used. So, I would expect an Amiga 500 with a 2 meg ram
card to run at the same speed as an Amiga 1000 with a 2 meg card.
Re: .1
Part of the motivation for the black and white output of the 500 was
that it would allow 4096 shades of gray instead of 16. They thought
they could appeal to the cheapie market by saying, "Look, you can buy
a cheap long persistence black and white monitor for under $100."
I think that was a mistake for two reasons.
First, you could always use a cheap black and white long persistence
monitor with the Amiga. You just had to worry that yellow and
green may look like the same shade of gray, and that neat yellow on
green display from your favorite spreadsheet would be totally unreadable.
Second, a very high percentage of households in the US have VCRs. I
would be willing to bet that almost all households that have Amiga
class computers have VCRs. One of the hot applications for the Amiga
is animation. Thus, color composite output is very desirable.
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