Bit 79 Computer

Archive · Post by **Archive** » June 27th, 2019, 9:14 am

posted by Mystic_Merlin on May 21, 2014:

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:

Archive · Post by **Archive** » June 27th, 2019, 9:14 am

posted by prince tomato on Dec 4, 2014:

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?

Archive · Post by **Archive** » June 27th, 2019, 9:14 am

posted by retro on Dec 4, 2014:

Moved to the repairs forum.

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

Archive · Post by **Archive** » June 27th, 2019, 9:14 am

posted by TriMesh on Dec 6, 2014:

prince tomato said:

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?

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.

Archive · Post by **Archive** » June 27th, 2019, 9:14 am

posted by l_oliveira on Dec 7, 2014:

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.

Archive · Post by **Archive** » June 27th, 2019, 9:14 am

posted by Mystic_Merlin on Mar 6, 2015:

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

Archive · Post by **Archive** » June 27th, 2019, 9:14 am

posted by Mystic_Merlin on Oct 28, 2016:

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

Attached Files:

../../attachments/basicbit79_d27128d-bi ... 27128d.bin

BasicBit79_D27128D.BIN

File size: 16 KB

Views: 118

Archive · Post by **Archive** » June 27th, 2019, 9:14 am

posted by l_oliveira on Oct 28, 2016:

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

Archive · Post by **Archive** » June 27th, 2019, 9:14 am

posted by Mystic_Merlin on Oct 29, 2016:

l_oliveira said:

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

Attached Files:

../../attachments/menubit79_2732-zip.22 ... 9_2732.zip

MenuBit79_2732.zip

File size: 1.2 KB

Views: 55

Archive · Post by **Archive** » June 27th, 2019, 9:14 am

posted by l_oliveira on Oct 29, 2016:

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).

Attached Files:

bit79.png

File size: 5 KB

Views: 150