SH-6BE-2/4-1 Ram Board upgrade question....

[BlueBMW]

I have a 2MB version of the SH-6BE-2/4-1 ram upgrade board coming in soon, and looking at the pictures of the 2mb and 4mb boards, is it possible to add 4 more ram chips to a 2mb board to make it a 4mb board?  I havent seen either up close, so I dont know what other components might be missing, or if the ram chips are even obtainable, but if they are, is it possible?

http://www.gamesx.com/wiki/doku.php?id=x68000:sh-6be-2_4m_-_memory_expansion_board

Also, will this board work on an XVI system?  Or are they designed only for the 10mhz systems?

[lydux]

Difficult to say... I can see 5 PEEL on this board, but the PCB is the same for both versions.
So, back in 1990's (and that's suitable nowadays as well), if I would be an hardware engineerer, I would create a universal design (PCB and PEEL), and let such differences be choosen using jumpers located somewhere on the PCB. So, 1 PCB and a unique PEEL programming. This will reduce products final cost, and reduce mistakes like placing PEEL for a 4M board on a 2M one.


See what I mean ?  

This could be verified as well on PIO-6834-2 :
http://www.gamesx.com/wiki/doku.php?id=x68000:pio-6834-2_4m_-_memory_expansion_board

There is some kind of jumper noted JP1 and JP2 located near the dipswitchs.
On a 4M version, JP1 is filled (picture taken from a korean website) :


So, I guess that's possible. You just have to find which jumper is the one you are looking for.
I can't see well, but it seems to be the third one starting from the left. If filled, it directly tight one of the PEEL's pin to ground. A common way to perform an hardware configuration.
The second jumper is probably hooked to the INH2 signal, which is a signal provided by the memory controller (OHM) that it start a DRAM refresh cycle, so have nothing to do with the amount of available ram banks.

On your SH-6BE-2, any RAM chip that is 1M x 4bit will do the job. Unfortunatly, not produced any more nowadays. But you can desolder 4 from an old 4MB FPM PC ram bank, chips should be the same.

Post a good picture when you'll receive it, just to verify these theory...

Have fun !