Porchy

C64c Original/JiffyDOS dual booting

General, Guides Comments Off

Oct 292011

Sometime back I modified my C64c with a switch to change between the original kernel and the JiffyDOS kernel. I did this because JiffyDOS is incredible for loading games from the SD2IEC but it doesn’t support loading from tape at all.
I needed to make another one up. Turns out I forgot how to! so here it is mainly for my own sanity.

Get a 27C256 eprom
Get a copy of the original C64c kernel. This should be 16KB in size, if its 8KB then that’s from the older breadbin C64.
Get a copy of the original C64 basic ROM. This is number 901226-01. This should be 8KB in size.
Get your copy of JiffyDOS for the C64. This should be 8KB in size.

Place all these files in a directory and open a command prompt (assuming your using Windows).

I renamed my files to something a bit more meaningful, “kernel.bin” “basic.bin” and “jiffy.bin”.
Type the following command:
“copy /b kernel.bin+basic.bin+jiffy.bin new.bin”

This creates a new binary file called “new.bin” and it should be 32KB in size.

Burn “new.bin” to a blank 27C256 eprom
Lift up leg 27 of the eprom so it doesn’t make contact with the socket pin.
Solder the common leg of a switch to pin 27
Solder one side of the switch to a 4.7k resistor connected to +5v
Solder the other side of the switch to GND

This should now give you a fully working switchable C64c.

Note: This only works for the newer C64c version. A 27C256 eprom isn’t pin compatible with a breadbin version without more modifications.
Also, JiffyDOS is still being sold and is not downloadable from my site nor will I provide it to anyone asking.

ZX Spectrum repair log #2

Oct 222011

The second of the ZX Spectrums I got recently, which is motherboard only, gave absolutely nothing on the screen
Replaced the usual ZTX650 for a ZTX651 and the one next to it which is a ZTX213.
This one also had the capacitor above them missing. Replaced this for a 4.7uF 50v one and tested.

All working again

Operation Wolf PALs added

PAL Updates Comments Off

Oct 222011

I dumped the 4 PAL16L8s from Op Wolf this morning.
~~I haven’t yet had this board up and running so these are untested. If someone could verify these for me I would be most grateful.~~

EDIT: Tested these now and they seem to work fine
They are:
B20-09.IC19
B20-10.IC84
B20-11.IC85
B20-12.IC92

New C64 game Prince of Persia

General Comments Off

Oct 162011

Today sees the release of a new C64 game. A fantastic conversion of Prince of Persia.
The game looks and plays just like the original versions across various other platforms.

This game requires an EasyFlash (or compatible) device to run. Naturally it also runs on VICE and most likely other C64 emulators, it also works on a C128.
Swoop on over to CSDb to download it

ZX Spectrum composite video mod

Guides, Mods Comments Off

Oct 152011

There is a very simple mod that you can do to bypass the RF modulator and use the same connector for a composite output.
It takes a few minutes to do this and works really well.

First job, remove the lid on the RF modulator.

There is a resistor connected to the centre pin of the RF output socket, remove this and bend it up out of the way.

On the outside of the RF module there are 2 wires leading from the modulator to the PCB. These are the VIDEO IN on the left and +5v on the right.

Remove both of these from the PCB.

There is a second insulated hole in the the side of the modulator unit that is unused. Get some wire and strip enough insulation off the end so you can feed it through and then solder it onto the centre pin that the resistor was originally connected to.

As im never going to be using the RF again I went ahead and totally removed the old VIDEO IN and +5v wires. I also removed the old resistor. This step isnt necessary but if you leave them in make sure they are insulated so they can short against anything.

Fire it up and check out the Spectrumy goodness.

Older Entries Newer Entries