03-01-2021, 04:42 PM
It seems that your BASIC comes from the short era when the last MWBASIC ROM was serialised.
A while after that, batches of masked ROMs were created with the serial number dropped (in an attempt to lower production costs).
However to have masked ROMs made incurred a NRE tooling cost thus a substantial quantity was required to negate these costs.
Masked ROMs are easily identified by their lack of sticker and UV window and also by the special production markings upon them.
The masked ROMS weren't just limited to the MWBASIC ROMs. They were also used for the Dual Font ROMs (on 13.5MHz) machines.
It's pretty simple to kludge up or obtain a replacement coreboard if that is your desire. Many others have done it.
It's even simpler if you drop the battery backup requirement.
The left connector contains all of the address A[0..15] and data D[0..7] lines along with the feedback /ROMSEL signal.
The right connector contains the power pins +10 and GND, the system control signals and a few decoded I/O port address select outputs.
Although not applicable to your case, the simplest coreboard consisted of two small boards; one with just a single ROM and PLD; and the other with a voltage regulator and connections to come control signals. These boards plugged into their respective sides of the baseboard and attached together with a small ribbon cable. It was designed specifically to provide access to the whole baseboard to simplify and expedite repairs. The little board didn't any RAM because the baseboard's CHAR and PCG RAM could be used after it had been proven to work by the ROM's diagnostic routine.
In your case, you could use later generation 32K SRAM, 16K ROM, 8K ROM and 4K ROM for the simplest standard coreboard set up for a 2MHz machine.
A while after that, batches of masked ROMs were created with the serial number dropped (in an attempt to lower production costs).
However to have masked ROMs made incurred a NRE tooling cost thus a substantial quantity was required to negate these costs.
Masked ROMs are easily identified by their lack of sticker and UV window and also by the special production markings upon them.
The masked ROMS weren't just limited to the MWBASIC ROMs. They were also used for the Dual Font ROMs (on 13.5MHz) machines.
It's pretty simple to kludge up or obtain a replacement coreboard if that is your desire. Many others have done it.
It's even simpler if you drop the battery backup requirement.
The left connector contains all of the address A[0..15] and data D[0..7] lines along with the feedback /ROMSEL signal.
The right connector contains the power pins +10 and GND, the system control signals and a few decoded I/O port address select outputs.
Although not applicable to your case, the simplest coreboard consisted of two small boards; one with just a single ROM and PLD; and the other with a voltage regulator and connections to come control signals. These boards plugged into their respective sides of the baseboard and attached together with a small ribbon cable. It was designed specifically to provide access to the whole baseboard to simplify and expedite repairs. The little board didn't any RAM because the baseboard's CHAR and PCG RAM could be used after it had been proven to work by the ROM's diagnostic routine.
In your case, you could use later generation 32K SRAM, 16K ROM, 8K ROM and 4K ROM for the simplest standard coreboard set up for a 2MHz machine.