OSI C4P Case I'm Filling Up

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falter
Posts: 31
Joined: Sun Dec 27, 2015 8:15 pm

OSI C4P Case I'm Filling Up

Post by falter »

I just bought a Challenger 4 case off ebay. Has the power supply and backplane too. I have the correct OSI keyboard, I have an original unbuilt 540b board, and a built 500 board. I know the 500 isn't technically the correct board but it's all I have at the moment.

The 500 board has a dead BASIC ROM, which was pulled from a Challenger 2 I had, and the good chip from this board going there. I've seen pictures of 500 series boards with OSI BASIC ROMs and what look like 2716 replacements installed.. you can do that right? I could burn a 2716 of the dead ROM and with some modifications use it in series with the originals?

I don't have an OSI RAM board (though I think I've seen reproductions).

I'm just debating what to do on the video front. I do have a 440 card.. but then I am stuck at 32x32. I have that unbuilt original 540b... do you think it would be a crime to build it? It is in the original box it was shipped in.. the seller said it was ordered from Super-COM supposedly after they bought OSI.
dave
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Posts: 710
Joined: Tue Sep 09, 2008 5:24 am

Re: OSI C4P Case I'm Filling Up

Post by dave »

Sounds like a great project. A 540B is the correct video board for a C4P. If you don't want to build up your original 540B board, then check the main OSIWeb page, and in the entry for the 540B card, you'll see a link to Gerber files for an extremely accurate reproduction. This repro has a bottom solder mask. Some boards had it and others didn't, but you can remove the *.GBS file from the zip archive if you don't want it (It's a zip file within a zip file.)

I just checked the price at JCLPCB.com. It's $21.30 for 5 boards, plus $22.27 for expedited shipping (~4-5 days) to Texas. Yep, the very reasonable shipping cost is greater than the cost of 5 new PCB's. The time from uploading the designs to getting them at your door is probably just about a week, or barely over.

You'll also find Gerbers for the 502 board if you want a cassette interface and BASIC in ROM (it will accept 2716 chips with some jumper settings), and the 505B, if you prefer a disk interface to Cassette and BASIC. The 505B interfaces to an I/O card on the back of the C4P. If you don't already have one of those, the gerbers are also available in the repository. All the links in the repository point to ZIP packages on GitHub.

You can turn a 502-based system into a disk system by adding a 470 card and some RAM and changing some Boot ROM jumpers.

Also, Jonathan (Glitch) has a memory board which I think he sells through his website and Ebay, and Grant (Klyball) has a 470K card, which is his own version of the 470 disk interface that also incorporates a data separator and RAM.

There are also a few more scans in the pipeline that haven't yet made it to the OSI reproduction GitHub (including the 440 board).

Cheers,

Dave
falter
Posts: 31
Joined: Sun Dec 27, 2015 8:15 pm

Re: OSI C4P Case I'm Filling Up

Post by falter »

Thanks Dave.

I'm leaning towards building my original board.. unless people here think it'd be sacrilege. Can't think of any reason to preserve it as is.. there's no kit of parts with it or anything.

Is there any reason I couldn't use my 500 board for the CPU? It's just going to sit around otherwise. But I'd only want to have it if you can replace the bad BASIC ROM with a 2716 like you can with the 502. I do have a separate OSI cassette interface board.. unpopulated.. forget the model number. I only have one disk drive for my OSIs.. a single 5.25 that is tethered to my Challenger I.
dave
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Re: OSI C4P Case I'm Filling Up

Post by dave »

I doubt anyone would consider it a sacrilege to build up the 540B board. At least in my opinion, that's the best thing to do with it.

The 500 board has jumpers to configure the ROM sockets for 2716, described in the manual.

You will need to reprogram the 1702A EPROMS to put the polled keyboard routine at $FD00, the 65V monitor at $FE00, and the BASIC support code at $FF00.

That will give you a 4K system, so you may also want to build up a RAM board, which you'd probably want to do with a 502 board anyway.

Unless you really want a cassette interface, you could just use the 500 board serial interface and a USB->UART interface to hook the system up to a host.

Is your cassette board a 430B? That's a great board, but the OSI system ROMs don't support the S1883 UART, so if you use it, you'd want to connect the Rx/Tx from the 500 board UART to the 430 board cassette circuit.
falter
Posts: 31
Joined: Sun Dec 27, 2015 8:15 pm

Re: OSI C4P Case I'm Filling Up

Post by falter »

I'm thinking this 500 may already be programmed for those things. That was the problem when I got it.. I tried to use it in serial mode and couldn't because it had the 65v monitor. I think it had been in a Challenger before it something.
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