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Once you do succeed in doing a reset, will it then do a full cold start and run basic?

When OSI sold the C1P Series II systems, using the 600 Rev. D board, they had the same SYN600 ROM that the earlier C1P systems had, which means there was no support of any kind in ROM for 48-character mode, or for writing to the port (at $D800) that controlled which mode the system was in. You shou...

When you do a cold start, some code and vectors (locations of I/O and other routines) are written to RAM memory. The "switch" code for the 48 char mode modifies these vectors and loads up some of it's own code. If you do a reset and a cold start, all the changes will be over-written. If you do a war...

New development adds fire and life. It's a good thing.

All the address and data signals go to the bus. The additional code could be put on an EPROM on a card attached to the bus.

If I recall correctly, 48 char mode will survive a reset, but not a cold start.

That is a discrete emitter follower and should be able to work fairly well.

Have you tried adjusting R5 and R9?

R10 will control the amount of color. Make sure you try that too, and see if the signal at pin 5 of the chip on the upper left is making it to the mixer base.

A lot of the modern monitor/TV sets load the video line with 75 ohms. This is technically correct for most 'real' video applications. However, back in the day, this was not adhered to on most computer based monitor systems. The video on most old systems (including OSI) back then used 7400 series log...

Sorry for how long this has been taking. Life throws you some real curves and fast balls once in a while. In any case, the RAM/EPROM board is now working and tested. Here it is on my 600B http://www.onebytecpu.com/images/electronics/osi_sb_me/ME19.jpg I loaded a BASIC5 ROM image Mike (MK14HAK) sent ...

A question for anyone that has experience with both the 600B and the 600D.

On my 600D, the first column of video seems to start 3 columns over from where the same first column does on the 600B. Like below:
Is this normal?

Welcome Mike!

Yes, I think that would constitute a useful exercise. Have at it!