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eprom/flash memory for a home made mv1b unibios?

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marcao_cfh

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Hello everybody. How's going?

I have a few mvs boards here, and one of them is a mv1b. Almost all of them have a unibios, but the mv1b. Since I just got a programmer, I had the idea to make my own unibios.

I did some research and there's info on what memory can be used for the mv1fz and for the mv1c, but no info on what memory can be used for the mv1b. All guides says to flash a dip40 eprom (27c1024) and use a adapter, or to solder 40 wires connecting the eprom to the board. I tried to find a sop40 memory with the same pinout as the 27c1024 but with no luck, I did found out there was a sop40 27c1024 but couldn't find it for sale.

And then I found on aliexpress a unibios for the mv1b in sop40 package, so there is a memory that can be used on the mv1b with no adaptations. But there's no clue on what memory they used.

So, any info/clues on what can I use to make a sop40 unibios for the mv1b?
 
I’ve never worked with the MV1B. I’ve only flashed UniBIOS 4.0 for the MV1C. I programmed over forty of them in one batch using Toshiba TC544200F-150 chips — a 40-pin drop-in replacement for the original BIOS with no modifications needed. As for using a 40-pin chip on the MV1B like you mentioned, I think you’ve got that part wrong.
 

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No, a 40 pin chip for the MV1B do exist. You can see aliexpress have them but some people bought it and found out it's a remarked chip. And I do know of one seller that have it but doesn't share what chip they use. All I know is it have the same pinout as a 27c1024 but on a sop40 package.
 
Unfortunally this doesn't work. This solution is for the MV1C. I'm looking for a chip for the MV1B, which have a way different pinout than the one used on the MV1C. I even talked to the OP of that thread and they didn't found a compatible chip for the MV1B.
 
No, I don't have knowledge to do this, but I did lots of researches and found out the MV1B bios follows the exact pinout as a 27C1024 used in a MV1FZ. But the MV1FZ uses a dip40 IC while a MV1B uses a sop40 IC. And the MV1C uses a chip with different pinout than the MV1B and MV1FZ, but for the MV1C a 29F400BB or 29F800BB can be used with a small modification.

I do know a compatible IC exists since aliexpress have them (but they're remarked) and I know a seller from my country found out a compatible IC which I'm not sure it's a sop40 or sop44 but it can be soldered into the board without any wires (but they remove the markings and don't share the IC model).

Edit: found out the maskrom used in the MV1B and the datasheet with the pinout. Pinout for the MV1C can be found here.
 
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Bah... use a multimeter on continuity and check the pins connecting that BIOS to the 68000 CPU. You can get the 68000 CPU pinout online. That will map most. Then you have power and ground pins... and chip enable.
 
The pinout is already known and the maskrom datasheet is available confirming the pinout, so it doesn't needed to be reverse engineered. The big issue is to find a chip that's pin compatible with it.
 
I posted the pinout in the comment just before the one you told me to reverse engineer it with a multimeter. But here are the links again.

As shown in the 2nd photo, the MV1B uses a TC531024 maskrom, which the pinout can be found in the datasheet here. Which is basically the same pinout as the 27C1024 and very different to the MV1C pinout.

The Unibios page also have a confirmation in the pinout.txt file that the MV1B pins match exactly the same pinout as the 27C1024.

And here's a link for a sop40 unibios for the MV1B, sold in my country but seller doesn't share the IC model number.
 
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OK... so you need a TSSOP packaged 5v flash chip and a small adapter PCB with castellated edges for soldering to the PCB.

Not that hard to do. JLCPCB can make those PCBs.

You'll need a TSSOP programming adapter for your chip programmer and make sure any read / write lines are held at the appropriate state to lock the chip into read and never write on the castellated adapater PCB.
 
Sorry but I think you misunterstood my question. I don't want to use a tssop with a adapter, or a sop with different pinout and a adapter. If that was the case I could just use a 29F400BB in sop package and a adapter.

I'm trying to find a sop IC with a matching pinout. If aliexpress sellers found one and the seller from my country found one, I'm actually surprised nobody else seems to know what IC they used.
 
I recently did a NeoBiosMasta VMC install on an AliExpress MB1B board that had the standard Unibios 4 installed. To install the VMC, you need to remove the on-board BIOS. I pealed the label back to see what chip is under there, and the aliexpress seller has erased all marking.

TBH. I suggest just going with a NeoBiosMasta or equivalent that will allow you to use regular 27C1204 EPROMs. The advantage here is that if anything happens in the future, you can diag the system (e.g. easily remove the BIOS chip and install Neo DIAG, or any other modified BIOS). Going with soldered on-board BIOS makes the 1B just as bad the original SNK design (where all the previous MVS PCBs had a socketted BIOS)
 
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