MV-1C Color Ram Error

[Grinwing]

Hey guys, I just finished installing the NeoBiosMasta and my 1C now comes up with this error:

Color Ram Banko Error
Address Write Read
00400000 5555 0010

What do I need to look at to fix this?

Additional, I did not remove the original bios.

 

[MKL]

Disinstal the NBM and see if the error goes away.

 

[MKL]

The color ram data lines are connected to a couple of octal flip-flops 74LS273 (where the RGB outputs are made basically) but also to the data bus of the CPU through a couple of octal bus transceiver 74LS245. On the MV1C the color ram and the LS245 aren't in standard chips like on the other MVS boards, they are inside the big quad flatpack GA2 which makes them impossible to replace in case they actually go bad. In this case however it's possible that the NBM is shorting some pins of the data bus of the CPU and somehow this results in a color ram error. That's why I say disinstal the NBM, see if it fixes things and in case try again.

 

[MKL]

The color ram data lines are connected to a couple of octal flip-flops 74LS273 (where the RGB outputs are made basically) but also to the data bus of the CPU through a couple of octal bus transceiver 74LS245. On the MV1C the color ram and the LS245 aren't in standard chips like on the other MVS boards, they are inside the big quad flatpack GA2 which makes them impossible to replace in case they actually go bad. In this case however it's possible that the NBM is shorting some pins of the data bus of the CPU and somehow this results in a color ram error. That's why I say disinstal the NBM, see if it fixes things and in case try again.

No idea why the color ram error has priority over other ram errors as the backup and work rams also have their data lines connected to the data bus of the CPU.

Razoola is the one who could answer this.

 

[Grinwing]

I decided to pull the original bios and reinstall the NBM. This did the trick. Now the board is working 100%

Thanks for the replies.

 

[Xian Xi]

When you had the original bios still on it did you lift the pins you were instructed to and soldered the others together?

 

[Grinwing]

Yep. Had both 10 and 12 lifted, soldered the wires to the pads and had a wire running from 21 to 10. I am guessing that I just wasn't making a connection as well as I thought.

I watched your video and it looked like your NBM was number 029. The two I bought are 028 and 030.

EDIT: That was my problem!! I had the wire from 21 tied into the CE wire and not going to the pin as it should have been. I feel stupid now for not being able to follow a simple picture! Hehe.

 

[Xian Xi]

LOL. Ah, looks cleaner now.

 

[Grinwing]

When I get around to doing the 1B, is it pretty much the same as the 1C where I just remove the Bios and solder the two wires to the pads or is there something else I will need to do?

 

[Xian Xi]

It's a little different. Here's the install PDF.

http://www.2dlives.com/nbm/install.pdf

 

[Grinwing]

I have a printout of that. I guess I was asking if it is similar to the IC process if I remove the original bios first? Is it as simple as just soldering CE to pad 2 and CO to pad 20?

 

[Xian Xi]

Yes, that is correct.