#A500 512k to 1 Meg? help
4 messages in this thread
While perusing the inner workings of my A500 (rev 6A on the board) in
anticipation of a hardware upgrade, I noticed the legend "512k/1 Meg"
heading a bank of 256k x 4 chips. What was intriguing about this was that
only 4 DIPs were visible, the other "sockets" being filled in with solder.
Having heard from a friend that the 500s are equipped with a 1 Meg Agnus, I
immediately have concluded that this motherboard's internal capacity is 1
megabyte, and to upgrade my system to a meg of CHIP RAM (still a bit
confused from PC days: why not call it "display memory"?) I need only
appropriate the necessary chips (256k x 4, 80 ns or thereabouts) and four
matching capacitors and add them to the motherboard.
Is this a recommended path, or should I hire a tech to install the
chips? Or, am I overlooking something else, and am I headed to a possible
disaster? Any suggestions/experience relating/comments would be greatly
appreciated.
Thanx for your time!
Peter
The older revisions of the A500 (rev. 5) used the 256×1 bit chips which
required 16 chips to get 512K. The newer rev. 6 A500's use 256×4 bit chips
which requires only four chips for 512K.
Another 512K could be added to the motherboard, BUT doing so would prevent
you from installing an A501-expander. (This includes some if not all
expanders that use the A501 slot.) The way the memory is "hardwired"
allows for one or the other. I've heard of hacks that allow both, but
haven't seen them.
The normal way to increase "graphics memory" (what CHIP memory is called
under AmigaDOS 2.04), is to plug an A501 or "clone" into the A501 slot and
cut a trace that normally maps the memory into "$c0-". With the trace cut
(jumper JP-7) the A501 would be 512K of CHIP memory. Other expanders such
as the BASEBoard, and the AdRAM540 can be configured with part of its
memory CHIP, and the rest either FAST or "$c0-".
Also, you will need the ECS Agnus (#8372a). IF you have it you will need to
"flip" the JP-2 jumper. This jumper is three small silver pads, the middle
& bottom pads are connected for 512K of CHIP. The top & middle pads are
connected for 1024K of CHIP. Only two of the pads can be connected, you
will have to disconnect the trace if you solder the other pad. The JP-2
jumper affects ONLY the Agnus to alert it to what mode to run in.
Ron.
The trace cutting also sets the resale value of your machine to about $0,
according to an area Amiga technician.
<catching all in capture> thanx for the info, will have to look further
into this system. Though I still heavily admire the intel-based PCs I am
astounded at the multitasking/multi-I/O capabilities of this machine, and
now know that Bill Gates's vision is seriously flawed in the Windows
department (4 megs for adequate multitasking, indeed!). Again, thanx for
the info/help!
Peter