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

Started by BlueBMW, May 14, 2012, 01:23:58 AM

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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?

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


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 :

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 ! :)