"New" OSI C4P and seeking advise moving forward.

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gekaufman
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Joined: Mon Nov 23, 2015 12:57 pm

"New" OSI C4P and seeking advise moving forward.

Post by gekaufman » Thu Feb 27, 2020 3:19 pm

Thanks to the tremendous efforts of Grant, Dave and Jonathan I'm happy to report I was able to build a C4P essentially from scratch. Jeff's notes were also hugely helpful.

I purchased a C4P case from Ebay that had the backplane, power supply and A-15 board only. I re-capped the power supply.

The case is now populated with 542C keyboard, 540B Video, 502 CPU and Glitch-Ram. It's very rewarding to now have a working, and reliable system.

Most went together well, although the 540B was the most problematic. The first board I constructed wasn't accessed by the CPU board despite a nice crisp display. I spent a long time on it but couldn't get it to work properly. I'll probably return to that at some time but subsequently built up two more boards (one with the color parts, one B&W) which both work nicely.

502 and 542C worked perfectly after addressing the modifications for 2716's on the 502 and known correction to the keyboard reset circuit.

For some strange reason the Glitch-Ram didn't like 10K pull-up resistors but a change to 4.7K fixed the issue. Great board! I've also built up a second board fully populated for Rom banking, 12 bit support and led display port. I hope to use this later with the 560Z.

Looking for advise as I move to a disk based system. I'd like to use Gotek/Flashfloppy instead of "real" media if possible as I don't have any MPI drives. I'm hoping the 505 board is produced soon. I have options of a 470K (I have one populated, but tested for ram support only) , 470 reproduction or a 505 board that I purchased used with no IC's off of Ebay. I've read thru the forum, but I'm a bit uncertain how to proceed. I guess the 505 would be nice as it has the connector for the A-15 already available.

Thanks!

- Gary

Jeff
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Location: British Columbia, Canada

Re: "New" OSI C4P and seeking advise moving forward.

Post by Jeff » Thu May 21, 2020 5:22 pm

Hi Gary,

Some things to consider:
1) The 505 does not have support for Basic-In-ROM. Basic (and other languages) are loaded from floppy.
2) A C4P can only have 4 boards installed at a time.

For me, I love having Basic In ROM, so I chose the 502. I plan to use the 470K which gives me RAM/ROM expansion as well as floppy support. I plan to use an Epson SD-800 which the 470K will support a 40 track 5.25" floppy and a 80 track 3.5" floppy.

I will need to modify the BOOT ROM to support Disk Booting, though.

/Jeff
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dave
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Re: "New" OSI C4P and seeking advise moving forward.

Post by dave » Thu May 21, 2020 7:26 pm

Jeff wrote:
Thu May 21, 2020 5:22 pm
Hi Gary,

Some things to consider:
1) The 505 does not have support for Basic-In-ROM. Basic (and other languages) are loaded from floppy.
2) A C4P can only have 4 boards installed at a time.

For me, I love having Basic In ROM, so I chose the 502. I plan to use the 470K which gives me RAM/ROM expansion as well as floppy support. I plan to use an Epson SD-800 which the 470K will support a 40 track 5.25" floppy and a 80 track 3.5" floppy.

I will need to modify the BOOT ROM to support Disk Booting, though.

/Jeff
Good points.

To switch to the H/D/M prompt, assuming you're using either a SYN600 or SYNMON-1 ROM, you just need to change the ROM select jumpers, as described here. The first 4 pages are the same for both ROMs.

I used to have a switch that would select between H/D/M and C/W/M.

Another options would be to install CEGMON, which supports both BASIC-in-ROM and disk boot.

Dave

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