NeoBiosMasta VMC Error "Memory card is write protected"

Derf

n00b
Joined
Feb 19, 2024
Posts
3
Hello! I installed a clone Neo Bios Masta VMC into a Neo Geo MV-1C board. It loads games and Unibios 4.0 just fine, but it complains that the memory card is failing the hardware test and when I try and format it, it says "memory card is write protected". I see mentions online that people with real memory cards have had that issue and it ended up being bad traces to (or cold joints on) the real memory card slot. Not sure what's going on here though since I have a VMC.

1.jpg2.jpg3.jpg

For one person's MVS (not OP), the issue was bypassed by soldering a wire from the write enable pin on their memory card to pin 6 of their HC32 chip, but I have no way to know what pin is for write enable on the FPGA of the VMC.

FWIW, I opted to keep the original bios onboard and lift pin 10 and 12, solder a wire from pin 10 to 21, solder pad 10 to pin 2 of the NBM, and solder pad 21 to pin 20 of the NBM - could this be related? I also replaced the default battery holder with one that can be swapped and have a LIR2032 in it.

Any ideas?
 

littlecharlie

Quiz Detective
Joined
Jan 10, 2018
Posts
83
I too got a clone of a vmc (mine from AliExpress, using Altera Max chip), indicating it was for Mv1B and mv1c.
The vmc works fine in a Mv1B, but when trying it in a mv1a, it showed this write protected message, and did not work.
Not a solution of your problem, but wanted to mention it.

Have you tried clearing the back up memory?

Also, this message might show up if the socket is not perfectly fitted into the 68k.
 
Last edited:

Derf

n00b
Joined
Feb 19, 2024
Posts
3
I too got a clone of a vmc (mine from AliExpress, using Altera Max chip), indicating it was for Mv1B and mv1c.
The vmc works fine in a Mv1B, but when trying it in a mv1a, it showed this write protected message, and did not work.
Not a solution of your problem, but wanted to mention it.

Have you tried clearing the back up memory?

Also, this message might show up if the socket is not perfectly fitted into the 68k.
Thanks for the reply! Sounds like the same one that I have. Did you also do the pin lift method on the original bios chip?

I wonder if the write enable pin just needs to be forced on/off, but I have no idea which pin that is.

I did try clearing the backup memory. No luck. Also tried reseating it twice, no change (unibios seems to work otherwise though, so I doubt it's a connection issue).
 
Last edited:

Neo Alec

Warrior of the Innanet
20 Year Member
Joined
Dec 7, 2000
Posts
12,256
FWIW, I opted to keep the original bios onboard and lift pin 10 and 12, solder a wire from pin 10 to 21, solder pad 10 to pin 2 of the NBM, and solder pad 21 to pin 20 of the NBM - could this be related? I also replaced the default battery holder with one that can be swapped and have a LIR2032 in it.
I would double check all of this. Got any photos?

The vmc works fine in a Mv1B, but when trying it in a mv1a, it showed this write protected message, and did not work.
Not a solution of your problem, but wanted to mention it.
From what I understand, the VMC isn't compatible with the MV1A. Only MV1B and MV1C.
 

littlecharlie

Quiz Detective
Joined
Jan 10, 2018
Posts
83
Thanks for the reply! Sounds like the same one that I have. Did you also do the pin lift method on the original bios chip?

I wonder if the write enable pin just needs to be forced on/off, but I have no idea which pin that is.

I did try clearing the backup memory. No luck. Also tried reseating it twice, no change (unibios seems to work otherwise though, so I doubt it's a connection issue).
I disabled the stock bios lifting the pins as per NBM guide. So, yes

To make the VMC work you shouldnt do anything special. You just disable the stock bios, you insert the VMC on top of the 68k, and you 're done.

I really don't know why it is not working for you.

I would double check all of this. Got any photos?


From what I understand, the VMC isn't compatible with the MV1A. Only MV1B and MV1C.
Actually they are (even though they say differently). Tried both the VMC that turfmasta was selling some time ago at arcadeworks, and also with another vendor I checked on Twitter, NeoJamma. They both work fine on mv1a.
The ones that are not compatible with mv1a are the ones from aliexpress.
 
Last edited:

Neo Alec

Warrior of the Innanet
20 Year Member
Joined
Dec 7, 2000
Posts
12,256
Actually they are (even though they say differently). Tried both the VMC that turfmasta was selling some time ago at arcadeworks, and also with another vendor I checked on Twitter, NeoJamma. They both work fine on mv1a.
The ones that are not compatible with mv1a are the ones from aliexpress.
It's interesting, because the MV1A is never mentioned, but in theory, yes, there's no reason it shouldn't work. The MV1A doesn't have any connection for the MV-IC card reader, so it's nice to have the option.
 

Derf

n00b
Joined
Feb 19, 2024
Posts
3
I got word back from the original seller. Apparently you can't use VMCs if you do the Unibios install method I choose (pin lift + wires), you have to fully remove the old bios chip. Worked right away for me after that. Definitely putting this info on ConsoleMods.org for others to find.

Not sure if this issue is limited to MV-1C only or if this issue only affects VMC clones.

Edit: Got confirmation from someone else that original NBM VMC units work fine with the pin lift method, so it is just an issue with clones.
 
Last edited:
Top