#Fat Agnus Upgrade ?
12 messages in this thread
I am confused about the "Fat Agnus" upgrade for the A2000.
At present, I have a "stock" A2000, with 512Kb Chip RAM and 512Kb Fast RAM.
If I go ahead with the Fat Agnus upgrade, will I have 1 Mb Chip RAM and
512Kb Fast RAM, or just 1 Mb of Chip RAM and 0 Fast RAM (i.e., does Fat
Agnus really add Chip memory, or does it just remap existing memory)?
Also, in the A2000, is it more than just a matter of pulling the Agnus chip
and replacing it with Fat Agnus, or are motherboard modifications required?
Ardie,
The so called "FATTER AGNUS" will give you allow all of 1 MEG of
memory on your A2000 motherboard (or the 512K motherboard and the 512K
expansion memory of an A500) to be used as CHIP RAM. So you will still
have a total of 1 MEG.
I think all you do is change the chip, and maybe reconfigure a jumper
or two. I be able to tell you for sure tomorrow, as I have one being
delivered then and will be installing it.
Just because it does not add any memory though, don't be fooled into
thinking it is not an important upgrade. Many people I have talked to say
it is one of the least expensive ($100.00 or so) and most important
upgrades you can make. A 512K Chip Ram Amiga that is multitasking might
have 512K available memory, but possibly most of the Chip Ram full. I have
had system crashes that I think are because operating close to full on the
Chip ram side, even though I had 200K of memory available.
I let you know more after I install it at do some experimenting.
Mike
Mike,
Please let me know how things turn out, particularly what is required
on the motherboard (i.e., is it just switching a jumper "cap" around, as I
did when I installed a second 3.5" internal drive, or is it cutting traces
and soldering). The former I feel comfortable with; the latter I'll spend
some extra bucks, and let it be my dealer's headache.
Also, thanks for the information on what the upgrade does. I know it
is an important one, and I want to do it soon. I'm just trying to get the
most bang for the least bucks ASAP, and I need more total system memory
BADLY (READ "I may be buying a 2 Meg 8-Up board tomorrow!").
Thanks,
Ardie Schneider[73475,1157]
Ardie
Installing the Fatter Agnus involves moving a jumper and cutting a trace.
But the real problem is pulling out the old one. It requires a special
tool (not just a chip puller) to remove. I tried to do it myself and
finally ended up getting a dealer to install it.
BTW, having 1 meg of CHIP makes a significant difference if you are doing
much mult-tasking.
Les
Ardie,
Although I am not 1000% sure, I do not think it requires any
modification to the motherboard, just a jumper like df1: required.
Considering that the 2000's and the 500's motherboard was built with the
upgrade in mind, (the 1000 cannot use the fatter agnus due to lack of
proper hardware) it would be hard to believe such extensive modification
was neccessary.
Mike
Moving up to the fatter agnus means a) pulling the old chip (which is a
large size, and needs a special tool to do it in a bullet proof way,
although it has been done with normal tools, but very carefully); a trace
cut (definite) and (I think) a jumper move, as well.
If you are uncomfortable with anything beyond a simple pull-a-normal-chip
and/or move a jumper (about my personal limits, btw), then you should spend
the extra $50 or so, and have it done by a shop which will be liable for
fixing anything they screw up (like your motherboard).
Ray Lewis
Ray,
Appreciate the information. The dealer I bought my machine from in San
Antonio in December of 1987 will do the whole job, parts and labor, for
$125 in a two-day timeframe. That's a bargain in my book, since I still
remember a bad experience a few years ago with a Commodore 1541 board I
botched (there's more than one of us out there).
Thanks,
Ardie Schneider[73475,1157]
Ardie,
Fat Agnus is simply the square chip agnus. You've already got
that, I presume you mean "Super Agnus"…and no…it has no memory on it's
own, it just allows the other custom chips to access a full Meg of RAM
rather than just 512K..so essentially, it's just remapping memory.
Yes, modifications must be made. A jumper needs to be switched (no
big deal there) and a very small trace…in a very crowded (trace wise)
area needs to be cut (that is a big deal if you cut one of hte other
traces!).
Don
Don,
Sorry for the nomenclature error. Thinking back, I do remember
getting the addendum with my A2000 way back when, which mentioned the
change in the Agnus chip to the Fat Agnus. Funny how those little details
slip away when you're not involved with them for a while. But you're
right, I want the chip that's I've seen referred to as the "Fatter Agnus"
or "One-Meg Agnus". I'm glad to know that the memory upgrade is separate,
since that's what I really need most desperately.
Sounds definitely like the kind of job I need to farm out to someone
who does it for a living, rather than trying to play computer repairman
myself, especially considering the trace cut is necessary.
Thanks,
Ardie Schneider[73475,1157]
Ardie:
You end up with 1 meg of chip ram and 0 k of fast ram. This can cause
problems with some programs which insist on having at least a little fast
ram to work in. There are two solutions: add some ram, so you have fast
ram (the preferred, but more expensive solution); or, use a utility that's
available here that fools the system into thinking that a little bit of
your chip ram is fast ram. I can't remember the name, since I have 5 megs,
I didn't need it. It may still be in AmigaTech lib 1 (new uploads), or it
may have been moved to either tools or system software libs. Maybe someone
around here remembers the name of the utility.
Ray Lewis
Ray,
I might not have to worry about that problem, since I've decided to get
either a 2 or 4 meg board before I do the upgrade. For not much more
investment, I might be able to join the 5-meg Amiga ranks RSN.
Thanks,
Ardie Schneider[73475,1157]