Development Page

Technical Documents

Bung's "DNES" Header document
Jeremy Chadwick's "DNES" header document (Updated, with a couple of errors corrected.)
Dr. PC Jr. Memory Map, kindly provided by Jamethiel.

Disassembly of the BIOS. Jamethiel has disassembled and commented the code found in each bank of the BIOS. This is interesting reading... :-)

Dr. PC Jr. BIOS ...And here is the BIOS in question. This is a dump I made of the 27c256 EPROM inside of the Dr. PC Jr. It does not work as a standard iNES ROM, because of the unique ROM paging mode of the PC Jr. I have verified the integrity of this dump by writing the data to an EEPROM and using that inside the Dr. PC Jr. The internal date in this BIOS is 1996.

Conversion Tools

iNES 2 DNES This is a DOS tool that converts iNES ROMs to the Dr. PC Jr.'s native format. It is obsolete now, though. See below.
QND This is a DOS tool that converts iNES ROMs to other formats, including the Dr. PC Jr.'s native format. You can find it at

Files & Goodies

Dr. PC Jr. DOS disk IMAGE This is a zipped file of a disk image of the PC Jr's DOS disk. A program called DiskDupe (Windows version is good) is required to copy the image to a floppy disk. You can find it perhaps here.
Dr. PC Jr. DOS disk contents list I've written a brief description about each file on the disk.

Dr. PC Jr. Games disk 2 -- File no longer available on this page. This is a zipped file containing most of the games/programs on the second games disk. They include such things as a Minesweeper game, pronunciation tutor, architect, facemaker, and a typing tutor. The first games disk evidently contains pirated first-generation Famicom games, so you won't find it here. Those games suck and are easily found on a multicart anyway.
Dr. PC Jr. Games in iNES format I've converted some of the PC Jr games into NES ROMs for use in emulators. Some of them simply won't work because they expect the extra PC Jr hardware, so they aren't included here.

EC/CE -- File no longer available on this page. English-Chinese/Chinese-English Dictionary for the Dr. PC Jr. This one's interesting. Search for a word in either English or Chinese, and it'll pronounce it and give the definition for it. The dictionary is limited compared to the popular portable electronic dictionaries, but it is intended for children, after all.
Unzip this Zip archive directly to a floppy disk, and stick it in your Dr. PC Jr. to get it to load up.

CATalogue for the PC Jr.
This is the first ever homemade program for the Dr. PC Jr.'s SMDOS system. It decodes the information stored in product barcodes (UPC, ISBN, etc..) that is sent from the :Cue Cat barcode scanner. Cuecats are available for free from U.S. Radio Shack stores, as well as through subscriptions to certain magazines. It's a cool product, especially if you can hack it and use it for your own evil purposes! >:-)

Here are some screenshots from CATalogue. You can download it by clicking on the title above. Read the included readme file, and you should have no problems if you follow the steps!

Please e-mail me if you have any questions or comments.