Dual JiffyDos Kernal ROM installation with hidden wires on the Commodore C16

 

As there are problems loading software using other media by simply installing a standard JiffyDos Kernal ROM I bought a Dual JiffyDos kernel with adapter board for my C16 with the aim improve loading times when using the SD2IEC. This ROM should allow you to return the C16 to its stock Kernal ROM by simply pressing any key and the C16 reset button at the same time.

 

I bought the Dual JiffyDos Kernal on eBay from an Italian seller who also makes the ROMS for the C64 and C64C. He was more than happy to programme my JiffyDos ROM for a PAL C16 and was very quick to send me the fitting instructions. Pretty easy in truth as it came with 2 wires attached to either side of the PCB with hook connectors and a clear diagram of where they should be fitted.

As I try and avoid any trailing wires showing on the co0mponent side of the PCB, I found a way to hide the wires by simply desoldering some through hole vias under the Kernal ROM chip.

A YouTube Clip of the process can be found at the end of this entry.

         

Tools required:

Soldering Iron

Cutters

Pliers

Screwdriver

Spudger

Vice

Scalpel or trimming knife

 

Components required:

Dual JiffyDos Kernal (I bought it from Ebay; item number: 314039913036)

30 A.W.G. Kynar Wire

40 pin Heatsink

28 Pin Heatsink

Slimline SSD Heatsink

Kapton or Insulating Tape

 

Firstly, strip down the C16; as I have an internal SD2IEC drive fitted, I had to remove that as well.

Now identify the Kernal ROM we are going to replace with the JiffyDos ROM.

 Then remove the original Kernal ROM; this can be done using either a chip extraction tool or a small flat blade such as a screwdriver.

I personally do not like using chip extraction tools as I find that it is easy to damage the legs on the IC if not pulled out straight

So I would recommend using a plastic spudger for this as there is less chance of doing any damage to either the chip, the IC socket or the PCB.

 Here is the wiring diagram from the seller of the JiffyDos ROM; As you can see there are two wires with EZ hooks attached on to them which connect to the long leg of R20 and the long leg of FB48.

If you are happy to have trailing wires on show inside your C16 this mod is relatively simple. However I did notice that the long leg of R20 had been painted on my C16 so you may have to scrape away the paint with a scalpel or trimming knife so that you get a good connection. It is also worth using a fibre pen on the long leg of FB48 to scrape away any rust on the leg before attaching the hook to it.

 

Here is a close up of the locations of R20 and FB48.

As I like to hide wiring wherever possible, I decided to remove the red and white wires on the JiffyDos ROM and replace them with 30 A.W.G Kynar wire. The Kynar wire will fit through ‘through hole’ vias which connect traces from the solder side to the component side of the PCB.

 

Remove the Red and White wires; they had been superglued on to the adapter PCB so care must be taken when freeing the wires from the PCB. Then it is a simple job of heating the solder joint then pulling the wires free from the PCB.

Now strip and tin 1-2mm insulation from the end of the Kynar wire; as I had two colours I decided to use my red Kynar wire to replace the Red wire and my Blue Kynar wire to replace the White wire.

Now solder the red wire on to the Notch end of the JiffyDos ROM.

And cut the wire to length; measure before cutting and give yourself some extra length just in case!

Now repeat the process for the Blue Kynar wire; I have a spool which has a wire stripping function to strip the Kynar wire but you could simply use your soldering iron to melt away the insulation from the Kynar wire.

And solder the blue wire to the other solder point on the JiffyDos ROM.

Now let’s see where we can feed the wires through the C16’s PCB. If you have a look within the IC Socket for the Kernal ROM you will see the two through-hole vias which are to be de-soldered.

I have identified the two Vias in question and have highlighted them below.

As it is easier to de-solder from the solder side of the PCB, I have highlighted the area in question then shown a close up of the two Vias to remove the solder from on the Solder Side of the PCB.

Next, de-solder the two Vias; as they are plated through holes there will still be a connection between layers even after removing the solder.

I opted to use my trusty old solder sucker for this job as I find that my de-soldering gun works better when it has a component leg to keep it in place whilst heating the solder.

Feed the Red and blue wires through the highlighted holes.

Then gently pull the Red and Blue wires through the PCB until the JiffyDos ROM is near the IC socket. Leave yourself enough slack so that you can easily remove the JiffyDos ROM after fitting should you need to remove it at a later date.

Now fit the JiffyDos ROM; Note that the notches of all the ROM chips face towards the left of the PCB.

Identify the solder point for the Red wire; it goes to the long leg of R20. Highlighted below is via to solder the Red Wire.

Route the wire and cut to length; below is my suggested wiring route.

Then tin about 1-2mm insulation from the red wire.

And add fresh solder to the Via shown earlier.

Now Solder the red wire on to the Via.

Now repeat the process for the other wire.

Identify the solder point for the original white wire.

And here is my suggested wiring route.

Measure and cut the blue wire to length.

Tin 1-2mm insulation from the blue wire.

Then add fresh solder to the Via.

Now solder the Blue wire to the Via.

From experience, it is a good idea to fix the wires to the PCB; this will prevent the wires from moving over any of the fixing holes on the C16 which would damage the wires when reassembling the C16.

 

For this I used small strips of Kapton tape but Insulating tape also works well. I would avoid using sellotape as the glue in sellotape tends to dry out after time.

That is the wiring complete! The new JiffyDos Kernal should simply work now. However, I am now paranoid about overheating my C16 so I decided to put Heatsinks on to the JiffyDos and Basic ROM as well as putting another heatsink on to my replacement CPU.

 

The problem we have with the CPU and the JiffyDos Kernal ROM is that we now cannot use a standard heatsinks as the adapter boards of both chips makes them sit too tall and would result in the heatsinks touching the  PCB of the keyboard.

 

So I dug out some of my SSD heatsinks which are much thinner than a standard heatsink. I found them on Aliexpress for around £1.50 for 2.

As the JiffyDos ROM is a lot shorter in length it is a good idea to cut down the SSD heatsink to fit the top of the JiffyDos chip.

I measured the length of the JiffyDos IC (which was around 36mm)

Then placed the heatsink in my vice; measured the 36mm and cut the heatsink down to size using a junior hacksaw.

Cutting the heatsink with a hacksaw will leave sharp edges on the heatsink so it is a good idea to file off the edges with a file.

Then clean the surface of the heatsink with some IPA alcohol to remove any dirt or grease.

Fit the adhesive thermal tape to the heatsink and trim off the excess using a scalpel or trimming knife; I did this on a wooden mat to avoid damaging my soldering mat.

Then fit the heatsink on to the JiffyDos ROM chip.

Now fit a 40 pin heatsink on to the CPU; I managed to order some slim-line 40 pin heatsinks for this purpose.

Finally fit the standard 28 pin heatsink on to the Basic ROM chip.

And reassemble the C16.

Now hook up your C16 and test!

The Dual JiffyDos Kernal ROM defaults to the standard Kernal as can be seen in the picture below.

To enable the JiffyDos Kernal, press the C16’s reset switch.

And as you can see in the picture below JiffyDos V6.01 has now been enabled.

At the above screen, type LOAD”FB16”,8 then press RETURN

And when you are prompted at the READY message, type RUN and then press RETURN.

Use the cursor keys to navigate the directories of the SD card then select the software of choice; I chose Manic Miner.

Using the JiffyDos kernel Manic Miner took just over 2 seconds to load! That is super speedy compared to the standard Kernal ROM loading speeds.

Then for comparison I loaded up the same game using the standard Kernal ROM. To enable the standard Kernal ROM you can simply switch off the C16 and start from scratch or you can hold any key whist pressing the reset button on the C16.

If you decide to software reboot as described above, you will need to reset the SD2IEC drive using the Reset switch on the SD2IEC.

Now load up the FB16 software from the SD2IEC drive.

Then for comparison load up the same software again.

The same software took a massive 25 seconds to load! What an incredible difference in loading times!

I played Manic Miner for a bit; I am still rubbish at it but at least I managed to get on to the second level using the keyboard for controls.

Thank you for taking the time to read this entry; I hope that you found it useful.

Below is the YouTube clip which complements this entry.

If you have any questions or queries about this modification then please feel free to leave a comment or email me directly at

alleged_geek@aol.com

The final modification I am going to do for the C16 is to make some Joystick adapter cables so that I can use my favourite Atari Sticks on this beautiful machine… I can only hope that this will improve my terrible gameplay!