peck@ral.rpi.edu (Joseph Peck) (06/13/90)
* Well, here it is. The infamous A1000 memory hack summary. Just to
start off I will state that this is by no means meant to be a complete
list of how to hack memory into a 1000, but merely an indication of
my current knowledge of what can and should be done. Here we go.
# There are two places where you can piggy-back ram chips: on the
motherboard and on the 256K expansion card.
On the expansion card you can fit an additional 512k of memory,
and this requires two layers of added chips. (every 512k added is an
additional 2 layers). There are two potential problems with this: noisy
bus lines from the connector itself, and heat buildup. The second is
probably the biggest problem. The additional ram almost touches the
amiga's case, and severely limits airflow. According to one person, the
chips get almost too hot to touch, although he has had no problems.
Additionally, there is very little room to work on the board, the chips
are very close together. Because of this, I would say that expanding the
expansion card is a risky approach.
On the motherboard is where most people have hacked their memory.
There is an article in the 1987 Amazing Computing Volume 2 Number 1 page 71 that
gives directions on adding 512k here, and includes some photographs and
a schematic. This article has been emailed to me, without photos :), and
several other people have it. It also includes comments on adding up to
1.5 megs, but gives no technical advice in that department. Apparently,
you have to add some simple decoding circuitry to handle it, but anyone
familiar with memory systems could do the job.
Here are some comments on the 512k hack. It appears to be a very
simple and straightforward job, given that you can wield a soldering iron.
The directions in the article are complete, and will get you 512k that
can be addmem'ed under 1.1. If you are using 1.2 there are two solutions
for you. (These mods should work under 1.3 but I don't know for sure)
As it turns out, with KS1.2 and higher, the system looks at the
available 2meg area for chip ram. This hacked on memory is then
configured as such, which would cause some nice crashes if left alone. There
is a program make512k that will remove this additional memory from the
system, and then you must addmem it as fast ram. This should work fine
so long as you can get at the startup-sequence. If you can't, Dave Haynie
has written an article on adding some additional hardware that causes the
memory to autoconfigure. It doesn't seem very complicated, and allows you
to run those strangely copyprotected programs with the increased memory.
I know some people are interested in even more memory, and I
mentioned adding 1.5meg. The answer is yes it is possible. However, there
are of course drawbacks. First of all you will need to add some of your
own decoding circuitry. Secondly, the chips will be stacked 6 layers
deep! This leads to noise from your solder connections and their proximity
to one another, and also causes tremendous heat. If I were to do this hack,
and I'm not, I would try to increase the airflow in the cpu case. Thirdly,
this many extra chips puts a heavy load on the internal bus. As a final
problem, you will have to modify the autoconfigure circuitry to handle the
extra memory. Oops. One more final problem. Some expansion boards already
use Dave's technique for simple autoconfigure, and only ONE device at a
time may do so. Check your memory expansions documentation.
A final topic brought up was the 1000's power supply. The answer is
yes it can support the memory hacks, including the one for 1.5meg. This is
assuming that the external expansion is only using the 1Amp that the amiga
guarantees it. Here are some numbers that I was sent:
Power usage for +5v only
A1000 motherboard ~2.5A (average)
2 floppy 0.3A (peak)
Joystick 0.1A (peak)
-----
3.0A (I know, 2.9A but we're rounding)
512K piggy-back ram 0.5A
so for 512k 3.5A
1M 4.0A
1.5M 4.5A
Now, I was also given that the power supply is rated for 5v@6A. Therefore,
if you add in the 1A for the external expansion port, the 1M and 1.5M
expansions still fit in. However, I would check the power consumption
of all of your added devices JUST TO MAKE SURE!
DISCLAIMER: Owing to the nature of some people and their enjoyment from
screwing over people who are only trying to provide wanted information,
I am not instructing ANYONE to actually dismantle their computer. I am
only stating what I know about memory expansions for the Amiga, and
informing you of what I think what I would do if I were to do one of these
myself. To that end I would like to say that I personally would add only
the 512k hack to the motherboard, and add Dave's autoconfigure circuitry.
Having stated what I shouldn't have had to, but this is America after all,
I would like to thank the following people for their comments:
Dave Haynie
K. C. Lee
Terry
Monty Saine
and everyone else whose mail I accidentally deleted
Good Luck
Joe Peck
peck@ral.rpi.edu
If any of my above statements are untrue, blatently false, etc. please
post the response so that anyone who goes to perform these hacks has the
benefit of the update. General flames may be directed to me, and NOT to any
of the people that I gave thanks to. If I were employed, these opinions
would be the opinions of my employer. . .daveh@cbmvax.commodore.com (Dave Haynie) (06/14/90)
In article <?G?$WG@rpi.edu> peck@ral.rpi.edu (Joseph Peck) writes: >If you can't, Dave Haynie has written an article on adding some additional >hardware that causes the memory to autoconfigure. It doesn't seem very >complicated, and allows you to run those strangely copyprotected programs >with the increased memory. Just a little clarification here. That hack I did way back gives you what's essentially the same memory decoding as on an A500 or A2000. What it does is modify the memory mapping logic on the A1000's daughterboard. The circuit detects an access to the 512K region starting at $00C00000, and fools the A1000's decoding PAL into thinking that's really $00000000, so that it'll generate DRAM selects instead of custom chip selects. The 1.2 OS on up have special code to add memory in this region. That's really not Autoconfig, but a special case. To the user, it ends up being pretty much the same thing anyway. >One more final problem. Some expansion boards already use Dave's technique >for simple autoconfigure, and only ONE device at a time may do so. Check >your memory expansions documentation. Real Autoconfiguring boards would never conflict with this memory. However, most if not all of the "hacked inside your A1000" type boards, like the Spirit Inboard, aren't true Autoconfig. These instead use the motherboard space at $00C00000, just like my mods to the Chris Erving hack do. So you most likely can't use the two hacks together, though a plain Chris Erving modification and an Inboard-type gizmo might peacefully coexist (no reason, other than power and noise problems, that they shouldn't). >To that end I would like to say that I personally would add only the 512k >hack to the motherboard, and add Dave's autoconfigure circuitry. That's what's in my A1000. I put that modification into it in early '86 or so, and it still works great. But, like any hack, the quality of the work may have a great deal to do with how well the thing works. And there are no guarantees; it's reasonably easy to damage your machine if you're not experienced with this kind of thing, and there's no guarantee that such a hack won't cause problems with other add-on hardware. My best advice is know what you're doing before you get into any of this. By the way, just in case anyone's planning to ask, I don't presently have a copy of the hack I wrote up, or the accompanying IFF schematic. I was running from floppies back then, and somehow that one got misplaced or trashed or some-such. The article is still apparently around on BBSs and similar places, but I won't be able to supply it, so don't bother asking. -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "I have been given the freedom to do as I see fit" -REM
monty@sagpd1.UUCP (Monty Saine) (06/14/90)
In article <?G?$WG@rpi.edu> peck@ral.rpi.edu (Joseph Peck) writes: > Here are some comments on the 512k hack. It appears to be a very >simple and straightforward job, given that you can wield a soldering iron. >The directions in the article are complete, and will get you 512k that >can be addmem'ed under 1.1. If you are using 1.2 there are two solutions >for you. (These mods should work under 1.3 but I don't know for sure) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Works fine, will last a long time. Assuming you have done Dave's autoconfig hack also. Additionally if you install a kickstart eliminator you can pick up another 256K via AddMem on the kickram. Enjoy Monty Saine
p554mve@mpirbn.UUCP (Michael van Elst) (06/15/90)
In article <12656@cbmvax.commodore.com> daveh@cbmvax (Dave Haynie) writes: >By the way, just in case anyone's planning to ask, I don't presently have >a copy of the hack I wrote up, or the accompanying IFF schematic. This has been saved in the wide areas of my up to then untouched harddisk. So if anybody needs this, just mail me. -- Michael van Elst UUCP: universe!local-cluster!milky-way!sol!earth!uunet!unido!mpirbn!p554mve Internet: p554mve@mpirbn.mpifr-bonn.mpg.de "A potential Snark may lurk in every tree."