Jr Cartridge blank for eprom

Hardware questions and modifications

Re: Jr Cartridge blank for eprom

Postby Shaos » Sat Dec 31, 2016 3:03 am

Technically possible to put 128KB into single cartridge without paging (and any other number of KB for example 512KB with programmatical paging that will require a few "period-appropriate" logic ICs around ROM). Anyway - I ordered prototypes for both 512K supercart from AlanH (with manual paging) and my quick-and-dirty replica of standard 64KB cartridge (without reboot feature because I think it is not healthy for machine to insert something when it's on):
Image Image
Image
Attachments
cart512k-top.gif
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cart64k-top.gif
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pcjrcart1.png
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Re: Jr Cartridge blank for eprom

Postby Trixter » Sat Dec 31, 2016 10:34 pm

Thanks for sharing!
You're all insane and trying to steal my magic bag!
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Re: Jr Cartridge blank for eprom

Postby Shaos » Tue Jan 10, 2017 7:37 pm

Link to order your 64KB board for 2 x AT28C256: https://oshpark.com/shared_projects/vnBQjk6B

I just got 3 from OSHPark, assembled one and it's working with one chip (32KB):

Image

and 2 chips (64KB):

Image

P.S. It is ONLY for EEPROMs (where A14 is on pin 1) and board is not for usual case - use it alone
Attachments
PCjrCart2.jpg
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PCjrCart1.jpg
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Re: Jr Cartridge blank for eprom

Postby Shaos » Wed Jan 11, 2017 6:05 am

Software for DOS to add signature and proper CRC to the image (PCJRCART.C): https://github.com/shaos/pcjrcart

For now it converts read-only COM-files (that can be run from ROM), for example (it's NASM):
Code: Select all
       org 100h

section .text

start:
       MOV     BH,7 ; 0 for DOSBox
       MOV     BL,4
       MOV     CX,1
       MOV     DH,18
       MOV     DL,0
       LEA     SI,[STRI]
NEXT:  MOV     AH,2
       INT     10H
       INC     DX
       MOV     AL,[SI]
       CMP     AL,'$'
       JE      KON
       MOV     AH,9
       INT     10H
       INC     SI
       JMP     SHORT NEXT
KON:   JMP     KON

section .data

STRI   DB      'Hello, world ! $'


Image

Later I'll add ability to convert any COM-files and simple EXE-files to ROM image (it will copy itself to RAM instead of running it from ROM as now)
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Re: Jr Cartridge blank for eprom

Postby Hargle » Wed Jan 11, 2017 7:08 am

It would be oddly cool to take this project:
viewtopic.php?f=3&t=364
where I converted a bunch of cartridge games to run off a floppy disk and convert it back to running entirely off cartridge again!

I don't quite recall how much storage space all of the games require. My project fits easily on a 360k floppy disk, but I seem to recall that nearly half of the disk is still blank, so a single cart that booted up with a little menu and allowed you to pick any of the games would be fun indeed. A PCjr megaGamesCart!
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Re: Jr Cartridge blank for eprom

Postby Shaos » Wed Jan 11, 2017 10:44 am

Hargle wrote:It would be oddly cool to take this project:
viewtopic.php?f=3&t=364
where I converted a bunch of cartridge games to run off a floppy disk and convert it back to running entirely off cartridge again!

I don't quite recall how much storage space all of the games require. My project fits easily on a 360k floppy disk, but I seem to recall that nearly half of the disk is still blank, so a single cart that booted up with a little menu and allowed you to pick any of the games would be fun indeed. A PCjr megaGamesCart!

About 230KB as I see - I think I can try :)
You even put offsets in the DETAILS.TXT - it's very helpful ;)

P.S. It's compressible to about 100KB and I think I can put it to TWO 64KB cartridges (or ONE future 128KB cartridge that I'm also going to make)

P.P.S. Without colorpaint (that requires DOS) archive will be even smaller than 100KB...
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Re: Jr Cartridge blank for eprom

Postby Hargle » Wed Jan 11, 2017 11:29 am

yeah, no point in adding colorPaint. I tried only because it was one of the last common cartridges out there and I had extra space on the disk.

Now all we need is some 3D printed cartridge shells to put your MegaGamesCart into. I'd definitely like to see this in a single 128k version.
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Re: Jr Cartridge blank for eprom

Postby Shaos » Wed Jan 11, 2017 5:35 pm

I don't think cartridge shell is required - bare PCB is perfectly ok ;)
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Re: Jr Cartridge blank for eprom

Postby Shaos » Wed Jan 11, 2017 9:29 pm

I just burned ColorPaint into my cartridge clone and run it from DOS:

Image

Without mouse it's useless, but at least it's working ;)

So in order to run it you need DOS - at least bootable disk - for example "Your PCjr Sampler" - just press Fn-B(Break) when it's drawing menu and then press Y to terminate batch job (ColorPaint cartridge should be inserted at this point) then simply write G in command line and Enter ("G" is DOS command from cartridge that execute ColorPaint application from DOS).
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Re: Jr Cartridge blank for eprom

Postby Hargle » Thu Jan 12, 2017 7:04 am

makes sense then why colorpaint when launched directly from my "carts on floppy" disk fails to load. No DOS == no worky. If I ever go back into that project for another update I will remove colorpaint completely.

I think I have a PCjr "Facemaker" cartridge that I should put on that disk instead.
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