24pin to 28 pin socket adapters for C64/1541 advice

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Zippy Zapp
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24pin to 28 pin socket adapters for C64/1541 advice

Post by Zippy Zapp »

Hi All,

I am learning about custom kernals and burning EPROMs and was wondering if anyone here has used this method of making their own kernel replacements/sockets for C64 and 1541 drives?

http://ist.uwaterloo.ca/~schepers/sockets.html

I think there are ready made PCBs and adapters that do this but for learning I wanted to try and build something myself so I can understand it completely. I am most interested in the section: Building a 28-24 Pin ROM adapter for 27128 EPROMs for the original C64's and 1541's. because that has info on switching between two banks. I am assuming you combine the two BIN files into one BIN file and then burn that to the EPROM.

So is this a good and correct method? I don't want to fry anything on the C64 with experimenting. :mrgreen:

Thanks!


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Re: 24pin to 28 pin socket adapters for C64/1541 advice

Post by eslapion »

See: http://blog.worldofjani.com/?p=757

This is essentially how you make a JiffyDOS for a VIC-20/C64 or 1541 drive.

The first half you fill with the normal ROM data, the upper half with the JiffyDOS data.

The 2764 and 27128, once programmed, have essentially the same pinout with ONE address pin being different. This is the pin you toggle between 0 and 5V to choose which half to present to the machine in which the chip and adapter is installed.
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Re: 24pin to 28 pin socket adapters for C64/1541 advice

Post by Zippy Zapp »

Thanks eslapion! So according to the image on the link you posted it looks pretty much the same as in the link I was wondering about. Excellent. So when I combine the ROMS to program, which I understand you use the command line copy command, you copy the DOS first then the JD second? Or is there a better way to combine the ROMs? I use a GQ-4X USB Programmer and I think there is a Combine Files To Buffer command.

Thanks for your help! I have ST M27C256B-10F1 and arriving today are ST M27C128A-10F1 and ST M27C512A-10F1, which I understand are good for 1571/1581 DOS+JiffyDOS. I have 24 pin and 28 pin sockets so I would like to give this a try.

Is there any information somewhere about adding it to Plus/4 which I believe already uses a 28 pin socket?

Thanks!
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Re: 24pin to 28 pin socket adapters for C64/1541 advice

Post by eslapion »

Zippy Zapp wrote: Or is there a better way to combine the ROMs?
I use Winhex.
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Re: 24pin to 28 pin socket adapters for C64/1541 advice

Post by motrucker »

Zippy Zapp wrote:Hi All,

I am learning about custom kernals and burning EPROMs and was wondering if anyone here has used this method of making their own kernel replacements/sockets for C64 and 1541 drives?
I think there are ready made PCBs and adapters that do this but for learning I wanted to try and build something myself so I can understand it completely. I am most interested in the section: Building a 28-24 Pin ROM adapter for 27128 EPROMs for the original C64's and 1541's. because that has info on switching between two banks. I am assuming you combine the two BIN files into one BIN file and then burn that to the EPROM.
So is this a good and correct method? I don't want to fry anything on the C64 with experimenting. :mrgreen: Thanks!
These adapters are pretty common place these days. You can even find them on ebay (this particular adapter is made by boulderdash, a member of www.REMOVED.com )
http://www.ebay.com/itm/Commodore-64-SX ... rmvSB=true
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Re: 24pin to 28 pin socket adapters for C64/1541 advice

Post by Tachyon »

Bah, use
cat stock-rom.bin JD-rom.bin >myfancynewROM.bin
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Re: 24pin to 28 pin socket adapters for C64/1541 advice

Post by Zippy Zapp »

Tachyon wrote:Bah, use
cat stock-rom.bin JD-rom.bin >myfancynewROM.bin
Yep. That is exactly what I ended up using. I did it on OS X and compared it to the Windows 7 Copy /b method too and it produces the same binary, of course.

Burned onto a 27128 and I used the socket stack method and it worked great.

I realize people make them already but I wanted to do it myself just for the fun of it.

I couldn't use the socket stack method on a Plus 4 as it is too high and the keyboard hits the top of the eprom. So for the Plus 4 I soldered the switch wires and resistor directly to a m27C256B EPROM and bent out the required pin and it works a treat.

My next task was to learn how to use eagle to design a PCB that included the functionality and I finally figured out how to design the adapter and be able to solder a 28 pin socket and 2 rows of round header pins for the 24 pin socket and a spot for the resistor and switch wires. Haven't sourced the round pin headers yet, so if you know of any by all means, post the link.
After I ordered the PCB from Osh Park ($8 for 3) I realized I missed one connection from pin 14 to Pin 20 so I will have to add a wire on those 3. I also want to find better library files for machined sockets that have round pads instead of oval ones so I can shave off some mm from the width.

All in all a great learning experience as I have never used eagle or done anything similar with putting these together.
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Re: 24pin to 28 pin socket adapters for C64/1541 advice

Post by Tachyon »

Zippy Zapp wrote:
My next task was to learn how to use eagle to design a PCB that included the functionality and I finally figured out how to design the adapter and be able to solder a 28 pin socket and 2 rows of round header pins for the 24 pin socket and a spot for the resistor and switch wires. Haven't sourced the round pin headers yet, so if you know of any by all means, post the link.
After I ordered the PCB from Osh Park ($8 for 3) I realized I missed one connection from pin 14 to Pin 20 so I will have to add a wire on those 3. I also want to find better library files for machined sockets that have round pads instead of oval ones so I can shave off some mm from the width.

All in all a great learning experience as I have never used eagle or done anything similar with putting these together.
You should post a tutorial, or just some tips, on getting started with a tool like Eagle for others that are interested in trying projects like that.
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Re: 24pin to 28 pin socket adapters for C64/1541 advice

Post by Zippy Zapp »

Thanks for the vote of confidence but I am a hack, at best. ;) But here are a few things I have learned:

1. Eagle can be very confusing to a beginner. All the tutorials I followed started with creating a schematic to an electrical circuit. Since I am no electronics expert it didn't really help me much. I just wanted a basic board since I already had the design, thanks to other people's drawings and creating the stacking socket method.

2. Load a board file (.brd) to a simple project to see how it is assembled and play around with the layers to turn them on and off so you know what is what. I also changed the colors of some of the layers so that they were distinct and easy to spot. The default color scheme has quite a few layers that are a grey color.

3. Experiment with the program. Use the library to add and place components on the board. I only had to use a 24 pin socket, a 28 pin socket and a resistor. I also needed a couple of pads with holes for switch wires. I used the resistor and deleted all the components but the two pads. You can create your own from scratch but this was easier for me to figure out.

Have fun while you are learning. I ordered some boards from OSH park and it cost a whopping $8 for 3. So I really don't know how well they will work but the price was cheap enough. It will give me an idea of how much smaller I can make it as it is hard to tell by looking at the screen. I already know I have to try to shrink the width a bit and add a trace to one of the pins.
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Re: 24pin to 28 pin socket adapters for C64/1541 advice

Post by ckoba »

http://vic-20.de/x1541/hardware/2364.html (instructions how to build the PCB) and https://oshpark.com/projects/MkuY6Dnn (PCB already uploaded to OSHPark fabricator) may be helpful here. These boards are about six bucks per three-set, and take very little extra real estate. The downside is that the resistors are SMD.
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