Simple Commodore 128 Upgrades

SkydivinGirl

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Hello fellow AmiBayers. :)

Today I decided to install a few mods in my Commodore 128 that I've had sitting around for a while. Here's what I installed:

The actual hardware installation on both of these was extremely easy because the Megabit ROM simply plugs into the open C128 expansion ROM socket and the JiffyDOS chips replace two ROMs on the board. The hardest part about these mods was modifying the case and heat shield.

I hoped I could find a way to mount the JiffyDOS switch without drilling into the case but, in the end, I decided to mount it above the cassette port. A drill at low speed made very little mess and a very nice, clean hole. Since I wanted to keep the heat shield, I had to do a little cutting.

There was a small bent-down part of the heat shield that would have touched the bottom of the JiffyDOS chip on the left side of the computer so I removed the bent down bit. The ROM-el chips sit much higher than standard ROMs so I bent the bits touching the chips up so they would touch properly. The majority of the rest of my time was spent cutting out the heat shield around the Megabit ROM since it's so big. :)

The last picture is the system all put back together with the 1541U-II, 64NIC+ and Final Cartridge III plugged into Jim Brain's X-Pander 3.

Ciao!

Heather
 

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LTAC

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It look like Chernobyl nuclear reactor before the disaster. :D
I love this COMMODORE 128 and also the 128D!!!
My collection is incomplete, no A4000, no CD32, no CDTV and no C128D :(

Like you, I must find some time to install my C128 and 1571 (failed).

Nice pictures!
 

jvdbossc

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I am out of words looking in 2010 at such an 8 bit baby :oops: But I don't know about the rom adaptor.. I know there are some rom sockets waiting to be fillled on the C128..

They were not popular local, since no use, since no software..........

I would say C=64 rules forever (y) But the C128 had much more potential, unused :Doh:
 

quarkx

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Great work Heather,
I still have to get a 1541U though and find a permanent place to set up my C128 now that I finally have the 80 C. monitor for it.
Ditch the RF shield though and get the heat sinks, they are cheap and you will be glad you did after removing and replacing it a few times.
 

SkydivinGirl

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"pimp my C64" a series starring SdG :D
LOL! I don't think I'd get many viewers. :wink:

Nice pictures!
Thanks LTAC! It was a lot of fun working on this earlier today.

Great to meet a fan of C128 here :)
Defnitely! I really like the C128; it's a great machine.

I am out of words looking in 2010 at such an 8 bit baby :oops: But I don't know about the rom adaptor.. I know there are some rom sockets waiting to be fillled on the C128..
I still use my 8-Bit Commodore computers much more than my Amigas. This is the first time I've ever used the Expansion ROM in the C128. The Megabit ROM holds a lot of programs in memory, such as disk and file copiers, hex editors, etc, and makes them available through an easy menu. It's like having a multi-ROM cartridge installed without taking up your cartridge port.

Ditch the RF shield though and get the heat sinks, they are cheap and you will be glad you did after removing and replacing it a few times.
Thanks! I still need to find a 9-Pin male to 9-Pin male 80-column cable to connect my C128's 80-column mode to my 1084S. I have a few of the 9-Pin male to round DIN type connectors but they won't work on my setup.

I don't plan on doing much more inside the C128 so I'm just going to keep the shield in place. I like the heat sink mod you did but I really want to keep the system in as close to original condition as possible. :)

Heather
 

quarkx

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Heather,did you get the 64K VDC?
 

SkydivinGirl

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Heather,did you get the 64K VDC?
The Megabit ROM has a 64K VDC test that I ran that said the VDC tested OK. I never installed the 64K VDC but maybe the previous owner did? How exactly can I tell? :)

Thanks,

Heather
 

Brataccas

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@ Heather - I have a C128 64k VDC board lying about somewhere, would it be of any interest to you? I think it`s the remains of a C128 i modified many years back.

Cheers,
 

TheCorfiot

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@Heather

The 64K VRAM upgrade is exactly the same as my TRS80 Coco upgrade.

If you have 2x4416 DRAMS then it is 16K, If you have 2x4464 DRAMS then you have 64K.

There are no links to change, simply unsolder the 2 chips & fit the new ones in place, pin for pin compatible, I would recomend using sockets so as not to stress the new DRAMS..
And by the way these are the 2 DRAMS that sit right alongside the 80 Column VDG under the metal Can....

Easy Peasy, you can do it, I'm upgrading mine when I get round to it.

TC (y)
 

quarkx

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To check if you have the VCD upgrade is simple (but a bit of work). under the RF shield, in the top half of the motherboard, you will see a smaller metal box with a screw holding the lid down. it is inside this box that you will see 2 "chambers" the VCD upgrade sits on the left hand side. if you see that the chamber has no second small board in it, then you don't have the solderless upgrade. The lid would be hard to put back on properly with this upgrade.

Here is the thread over at C128 and Pet Alive!

also I post the following info found in that thread:


The BASIC 8 program on the Megabit ROM requires an expanded Video RAM. In addition, the Maverick Copy programs will make use of the expanded RAM if present. The Maverick "64K VDC RAM Test" on the ROM will check your C128 for presence of the Expanded Video RAM.

The 128DCR came with the Expanded RAM. The regular C128 did not.

The following is an article explaining the Video RAM & instructions so you can install your own:

UPGRADE YOUR VDC RAM TO 64K
By: John Kress

Copyright 1986 Twin Cities 128
P.O. BOX 4625, Saint Paul, MN 55104

This article has been released for non-profit use only, provided the author's name and the above information are presented with the
article:

The very first time I had fired up my new C-128, I loved the 80 column screen. I remembered the days of my Vic-20 with 23
characters per line. Now I had a computer with an 80 column screen, and I thought to myself 'Now I own a real computer'. Then I
came across a very basic 80 column graphic program that used a joystick and thought that this is great, but it is too bad that you
can only use one color on the screen at a time, and secretly dreamed of owning an Amiga. Then came the day that I found out that
the memory dedicated to the Video Display Chip could be expanded from the stock 16K to 64K of RAM. Right then and there, I was
hooked (I believe it's referred to as 'Technolust' in these parts) and wanted to learn all I could about expanding the RAM to its
maximum.

I should explain a bit about the VDC and its RAM. The 80 column screen uses a separate chip for screen processing, and that chip
has its own dedicated RAM. Unlike the VIC chip for the 40 column screen, which uses part of the BASIC RAM for screen memory,
the VDC has 16K of RAM tied into it that cannot be accessed in the normal peek and poke method. The VDC is in some ways a
separate processor that operates independently from the rest of the C-128 and is able to work at a faster clock speed than the VIC
chip. That is the reason why the video display goes blank on the 40 column screen when the FAST command is issued.

Why expand the VDC memory?

Since my major computer interest is GRAPHICS, I wanted to find out how things might be improved with more memory. One of the
first things I pondered was the graphics screen with attribute RAM for color. That would allow more than one color on the screen;
although you're still limited to just one color in any 8*8 pixel area, you can have more that one color. Then there is the ability to
have a combination of screens in VDC memory, up to 4 graphic screens, up to 13 text screens, or a combination of both. There is
also the possibility of making up different fonts (print styles) in memory and being able to change them.

(Editor's note: Readers who attempt this process do so at their own risk. Neither this author or Twin Cities 128 will take
responsibility for losses due to the attempted execution of the process outlined in this article.)

The parts you will need are :

* Two (2) 18 pin IC sockets, to be used to hold the RAM chips. These can be found at most any electronic supply house.

* Two (2) 4464 Dynamic RAM Chips with a speed of 120 ns. Yes, that's correct, 4464 RAM chips. I know that the Commodore
Programmers Reference Guide says 4164 RAM chips, but 4164 chips are a sixteen pin type. The 4416 chips are an 18 pin type so if
you try to use the 4164's you'll have two extra holes and nothing will work right.

You will need the following tools:

Wire cutter or nippers.

A small pencil type soldering iron (35 watts is be enough, much more may get too hot.)

Some rosin core solder or better yet, solid core solder and a paste type non-corrosive flux.

Small phillips screwdriver.

Small pair of pliers.

Now you're ready to begin:

NOTICE: Integrated Circuits are extremely sensitive devices and very sensitive to static charges. A small static shock to a IC is as
deadly to them as a bolt of lightning would be to a human. Take extreme caution to avoid a static discharge to the computer.

First thing to do is remove all power cords and serial connectors from the C-128. This means everything, since the main board
must be removed from the machine.

Turn the computer over and locate and remove the six (6) screws holding the computer case halves together, then carefully
separate the halves. This is critical, because the keyboard and power light connector along with a ground braid for the keyboard
are still connected and could be damaged. Carefully remove the screw holding the ground braid, along with the connectors for the
power light and keyboard, taking note of their proper connection. I found that the keyboard connector was installed with a brown
wire closer to the power switch, but things may be different on other machines.

The next step is to remove the screws holding down the computer board and the ground casing. There were six screws around the
perimeter of the main board/shield assembly; remove all of these. Then you must use the pliers to gently bend the tabs holding
the upper ground casing to the lower casing. There is one more screw mounted on the ground casing in about the top middle; this
must be removed also.

There is one spot where the casing halves were soldered together on my computer and that was in the front right side, near where
the numeric keypad sits. Carefully unsolder the halves and lift the top half away. What you now see is the main board with a small
metal box on it, near the center of the board. The chips that need to be replaced are inside that metal box.

Inside the box are both of the screen controllers, the 8564 Vic chip and the 8563 VDC chip. Remove the lid to the box and locate
the two chips that are identified on the circuit board with the marking U23 and U25. On my board these chips were labeled with a
large F and the part number MB81416-12. The number may vary due to the manufacturer, but the markings on the board will
identify the correct chips.

Now for some very delicate surgery. Since the RAM chips will be discarded, I suggest that you carefully cut away the chip pins
(leads) from the body of the chip. This will make removing the remaining portion a lot easier, and leaves less of a chance of
damaging the main board than trying to remove the whole chip intact. The next step is to carefully unsolder the pins from the
circuit board. Make sure that you are working with the correct area, as things do get rather confusing when you turn the board
over and notice all of the many soldered areas. You might be best off to mark the correct area with a felt tip pen to avoid
confusion.

The next step will be to install the IC sockets into the circuit board. Try fitting the sockets into the board to make sure that they
will fit all of the way through the holes and that there is enough material poking through for a good solder joint. Also be sure to
orient the sockets with the small identification notch on the correct end of the board. The notch is printed on the board so you
should have no trouble.

When you have the sockets installed correctly, lightly bend the pins over to hold them in place, and you're ready to solder them in
place. Again be careful, as drips of solder can cause a short, and a cold solder joint will cause a poor connection.

Now you're ready to install the 64K chips in the sockets, carefully inspecting the pins for proper alignment. Most of the time, chips
will be made so that you will have to bend the pins inward, toward the center, to fit properly in the socket. But too much bending
will break off a pin.

Once you've installed the chips, you're ready to start the reassembly process, just reverse the disassembly steps and make sure to
solder the ground case halves again. Reconnect your cables and power up the computer.

If all went well, you should see NOTHING UNUSUAL. The same old cold start up message and nothing different. Some of you might
notice a different pattern on the screen when the initialization process is going on, but after that, you should see the same OLD
SCREEN. The cold start routines for the C-128 initialize the VDC registers, and the VDC chip is told that it still has the 16K chips
in it. In order to tell the VDC you've upgraded the RAM, you will have to set bit 4 of register 28. When this is done, for some
reason, the character information gets scrambled, but a call to the COPY ROM routine at $CE0C clears the problem.

If your screen does not appear the way is should, look for a cold solder joint or a pin that is not installed into the socket correctly.
I found that when I tried to remove the old chips in one piece, I had damaged a portion of the copper foil on the circuit board and
had to trace the circuits out and install a jumper wire from the 8563 socket to one of the RAM sockets.
 

chiark

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Just for clarity, the C128D (non-cr version) only has the regular VDC: I've just upgraded mine to the 64kb VDC and tested with Maverick. All works well :D

Next step: retr0brite!
 

SkydivinGirl

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@QuarkX

Thanks for the detailed information! I guess I'll have to disassemble my C128 one more time to verify the 64K VDC is in there, but I did run the Maverick 64K VDC test and it says it passed so I'm pretty sure it's in there. :)

@chiark

I didn't realize the 128DCR already had the video ram in there! One more reason for me to get around to testing the two 128DCRs that I have. Unfortunately, I only have one keyboard. :(

Heather
 

xc8

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@heather

Can you run the 1541U and NIC at the same time with this expander?

Chris
 

SkydivinGirl

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@XC8

Yes, you can! I was using the 1541U and the 64NIC+ cartridge at the same time. Simply push all the switches in each slot down to the ON position and they work in harmony. :)

Heather
 
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