Bit 79 Computer

Hello guys, I found a Bit 79 Famiclone computer on a pile of junk recently. It's a funny looking micro with parallel or serial port printing, tape in/out and a famiclone.
It turns on but shows a brown or green screen. Apparently it's supposed to show a boot screen with the choice of running a built-in basic or the famicom cart.
The machine seems to have been tinkered with as I can see excessive flux on the SRAM and one of the EPROMS has its pins sanded. I believe one of the 2 is the culprit but I'm more convinced it's the EPROM, it's in bad shape.

So as I found very little information on this device other than this page,
http://famicomplus.blogspot.com/2013/05/famiclon-computadora-bit-79.html
I was wondering if by any chance someone had a dump of these EPROMS. One is a 27128 and the other one has no marking but I'm guessing it's a 2732 or 2716.

Here are a couple of pics:

 

hi all,
i just got a Bit79 famiclone too,
mine came with a 5v power supply while all my other clones run on 9v.
it doesn't look original, so i wonder if it is at the right voltage.
does anyone know the specs of the original power supply?

 

Moved to the repairs forum.

Also, be wary of that link in the OP - it redirected me to a fake Flash download.

 

I have no idea, but I can't see any voltage regulator on that board - which strongly suggests that it does use a 5V supply. Try plugging it in and measuring the voltage across the power pins on the chips.

 

At least it's using discrete chips and should be easy enough to find replacement chips.

Are you on PAL-Land ? That hardware is "PSEUDO PAL". It runs on NTSC Famicom specs, but with 50z video timing and PAL color format.

Basically "Dendy style" hardware, optimized to run Japanese Famicom (or copies of) in PAL-Land.

 

Sorry for the late reply, I didn't log for a while and hadn't notifications turned on.

@ Prince Tomato
Yep the power supply is 5V DC +C- 1A as this photo confirms:
http://2.bp.blogspot.com/-qDLCLNzBN...AhU/7N4uM0GYEeY/s1600/2013-05-26+13.07.44.jpg
Be careful as there's no voltage regulator on this computer as TriMesh pointed out, plugging the wrong power supply will fry the SRAM which may have happened with mine.
I would be very grateful if you could dump the 2 eproms so I can fix my unit

@ retro
That's weird, never had a warning accessing this site

@ l_oliveira
I indeed found mine in PAL territories

 

I finally repaired that thing. As I suspected the RAM was shot and the small ROM had a busted connection


I dumped and attached here the 16KB rom containing the BASIC; not the other one which is flimsy and only has the above selection screen.
Below are also some, if not all, the BASIC commands found in this ROM
If any one has the BASIC manual and is willing to scan it btw, it would be fun to try out the printing and LOAD/SAVE options.

Otherwise if anyone is willing to tinker with the ROM and disassemble it...

Code:

NEW..SAVE‚.LOADƒ.EDIT….RUN†.STOP‡.CONTˆ.LGR‰.HGRŠ.POKE‹.PEEK(Œ.DEFŽ.DIM..RND(..TAB(‘.AUTO’.GOSUB“.CALL”.DATA•.ELSE–.FOR—.GOTO˜.HOME™.INPUTš.RANDOMIZE›.CLEARœ.LIST..REMž.NEXT .PRINT¡.RESTORE¢.READ£.STEP¤.THEN¥.PLOT¦.RETURN§.TO¨.UNTRACE©.IFª.TRACE«.COPY¯.FRE°.TEXT±.END³.LET¹.>=º.<=».<>¼.AND½.OR¾.NOTÀ.ABS(Á.ATN(Â.COS(Ã.EXP(Ä.INT(Å.LOG(Ç.SGN(È.SIN(É.SQR(Ê.TAN(Ë.STR$(Ì.CHR$(Ó.VAL(Ö.LEN(×.INKEY$Ú.FN

 

The other rom is needed too. It contains the font.

 

Ok, I'll try to dump it. You know that from looking at the first ROM?
I noticed that after some time using it, there's actually some character issue and flickering. I need to monitor the +5V rail near the ram as I believe the problem is located in that area.

Here you go. You were right, this 4KB ROM contains the character set. Thanks to you I realized the flickering was due to a faulty connection on one of the pin of that ROM, everything is smooth and operational now

 

There's a missing data line output on your dump. It's bad. Either the chip is bad (the same gray line will appear on the tv at the real system) or you had poor contact on the chip reader.

By the way around the middle of the character table there's some fuzzy stuff which look like actual 6502 code (the NES can use the graphics ROM to store code and some games actually use it that way).

 

Sorry here's the good dump, D6 pin is indeed causing all sorts of connection problems
Playing around with the machine, here's what I found out so far:
- The available memory for BASIC is only 6271B
- You can access the RAM from -65535 to 65535
- 45 Basic shortcuts are available via the combination of the Basic key + pretty much all the other keys

You mean at &0C00? Here it is:

Code:

A2 23 A0 03 20 C2 C1 A9 00 8D 00 20 8D 01 20 A9 1B 85 00 A9 06 85 02 A9 61 85 01 20 4E 06 A0 23 A9 06 85 02 A9 7C 85 01 20 4E 06 A0 62 A9 06 85 02 A9 97 85 01 20 4E 06 20 C2 C1 A9 80 8D 00 20 A9 18 8D 01 20 A9 00 8D 05 20 8D 05 20 60 8E 06 20 8C 06 20 A0 00 B1 01 8D 07 20 C8 C4 00 D0 F6 60 80 81 82 83 84 85 86 87 88 92 93 94 95 96 97 98 00 A4 A5 A6 A7 A8 A9 88 92 00 00 89 8A 8B 8C 8D 8E 8F 90 91 9B 9C 9D 9E 9F A0 A1 00 AA AB AC AD AE AF 91 9B 00 00 28 43 29 20 43 4F 50 59 52 49 47 48 54 20 42 49 54 20 43 4F 52 50 20 31 39

That's interesting, I guess they were fighting for every bit or space when they made that thing
It looks like it's to display the lower part of the intro screen with the Chinese logo and copyright.
For the top part I found it in the Basic rom, in reverse, at &043F

 

As you picked my curiosity with that code I made an attempt at disassembling it:

; code portion at &0C00 of the Menu rom to display the intro screen

A2 23 __LDX #$23
A0 03 __LDY #$03
20 C2 C1 __JSR $C1C2
A9 00 __LDA #$00
8D 00 20 __STA $2000
8D 01 20 __STA $2001
A9 1B __LDA #$1B
85 00 __STA $00
A9 06 __LDA #$06
85 02 __STA $02
A9 61 __LDA #$61
85 01 __STA $01
20 4E 06 __JSR $064E
A0 23 __LDY #$23
A9 06 __LDA #$06
85 02 __STA $02
A9 7C __LDA #$7C
85 01 __STA $01
20 4E 06 __JSR $064E
A0 62 __LDY #$62
A9 06 __LDA #$06
85 02 __STA $02
A9 97 __LDA #$97
85 01 __STA $01
20 4E 06 __JSR $064E
20 C2 C1 __JSR $C1C2
A9 80 __LDA #$80
8D 00 20 __STA $2000
A9 18 __LDA #$18
8D 01 20 __STA $2001
A9 00 __LDA #$00
8D 05 20 __STA $2005
8D 05 20 __STA $2005
60 __RTS
8E 06 20 __STX $2006
8C 06 20 __STY $2006
A0 00 __LDY #$00
B1 01 __LDA ($01),Y
8D 07 20 __STA $2007
C8 __INY
C4 00 __CPY $00
D0 __BNE
F6 60 __INC $60,X

80 81 82 83 84 85 86 87 88 92 93 94 95 96 97 98 00 A4 A5 A6 A7 A8 A9 88 92 00 00 89 8A 8B 8C 8D 8E 8F 90 91 9B 9C 9D 9E 9F A0 A1 00 AA AB AC AD AE AF 91 9B : this looks like coordinates, graphic coordinates?

00 __BRK
00 __BRK

28 43 29 20 43 4F 50 59 52 49 47 48 54 20 42 49 54 20 43 4F 52 50 20 31 39 38 39 : copyright text at the bottom in ASCII

Hoping it might help...I must have too much time on my hands at the moment lol