OSI 541 Board

[dave]

I found this reference to the OSI 541 board. This confirms it's a high-res board, providing 256x512 graphics, overlaid on the character graphics. Apparently there was a similar board for the C1P providing 256x256 bit-addressable graphics.

Jeff, I think your system was either upgraded with a 541 board, or was a late-model offering by Ma/COM before they changed the name of the system to the C-100. Take a look at this spec sheet:

MA/COM C-100

Very interesting. I'd love to find a set of schematics for that board, if any exist. . .

Dave

[Jeff]

WOW WOW WOW!

Now I REALLY have to get this system up and running, although I have no Idea how/where I am going to get a System disk for it. Thank you for digging this info up.

I found this sticker on the back of the unit, so perhaps it really is a Ma/COM Keymate C-100!

Screen Shot 2014-04-16 at 5.24.23 PM.JPG (111.31 KiB) Viewed 11765 times

[Jeff]

I sent you via email, my efforts to date to trace out the schematic of the 541 board. I am working from hires photos of the top and bottom of the board first so as not to damage the board itself. I sent the file via email as it was too large (36MB) to attach. I am still not finished. I am hoping, once I get new 8T26's that the board will come to life, and through the trace to determine where the graphics card resides in RAM. Also, there will be some sort of address that needs to be accessed/written to to turn on the graphics mode(s).

Cheers
-Jeff

[Jeff]

I have emailed you the latest schematic. Feel free to post it.

/Jeff

[Jeff]

I completed the schematic today. Please check your email.

/Jeff

[Jeff]

Well it's been a year to the day, I'm wondering if the schematic has yielded any secrets. ;-P

[MK14HAK]

Jeff I may have the 600 version. I haven't been near it lately as its part of my RevB system that needs a major tidy up.
Can you PM a link to your schematic. Im guessing there may be some control addresses in the DXXX area perhaps. I have no software either but happy to collaborate on something .

[dave]

Mike,

The link is here.

Dave

[MK14HAK]

Jeff,
It looks like data bits D1 and D4 ( via U4F ) in the Color RAM address ( is it $DEXX ) space control CHARGEN / PCGRam selection via U5G F/F and U3G Gate to select data from CHARGEN or RAM via U6F . D-F/F below that @U6G controls preset and clear of the F/F and has a pwr reset state.

Do those bits also control color on a 540B color bd ?? Im guessing they dont.

Display RAM looks like its sequenced by decoding at U3F via U2J -10 DIS signal enabling the RA bus. Selections on the 540B using J5 U4D are involved here ?

It would be good to detail the 505 and 540 mods also.
And my programmable graphics board by the way is not a 600 version of the 541 but from Practical Electronics. No 48pin expansion skt but shifts the CHARGEN also and gives only 256*256 if I remember correctly.

[Jeff]

My C4P crashed while booting from floppy today, and showed me an interesting screen.

541 Output.jpg (183.57 KiB) Viewed 11047 times

Here is a closeup:

541 Output coseup.jpg (137.07 KiB) Viewed 11047 times

I wonder what memory address triggered this.

/Jeff