osiweb.org

Hi Steve, I've uploaded the SAMS manual, but haven't yet updated the web page. Will do so tonight. Meanwhile, you can find it at: http://osiweb.org/manuals/SAMS_C4P.pdf Also, I've uploaded a large number of Peek 65 issues, many of which were donated by Earl Morris, and the rest of which I recently a...

Just saw your post. I actually bought a nearly complete PEEK(65) collection on ebay a few weeks ago, and have scanned all of them into PDFs, and also had obtained some other OSI documents in PDF form from Mark S. a while back. I will be posting everything on the web site soon. First, I will get the ...

Yes, both chips are bidirectional buffers, and the only difference is that the 8T26 is an inverting part, and the 8T28 is a non-inverting part.

American Microsemiconductor has 8T26's and 8T28's in stock for a reaonable price. If you get a bunch of one chip or the other, there are some places you can replace 8T28's with 8T26's and vice versa. For example, you can replace all the bus drivers in a C2/4/8 system with the same type, either th '2...

I think a PIC could do it, especially if you use one with lots of I/O lines and a 40 MHz clock (or even a 20 MHz clock). The 540 boards used a 12 MHz dot rate. If you use an 8-bit shift register at the output, you can probably make the timing. I wonder if it would be possible to hijack the UART for ...

WIth only a logic probe, you can fix the computer, but you have to be more of a detective than if you had fancier equipment. Start out by probing the CPU clock lines to make sure there are pulses. Unlike the 505 card, the 502 gets the clock signal from the clock divider chain on the 540 board. I don...

Cool. I'd start by removing the mod, and the RAM board, and powering up with just the video and CPU cards, positioning the CPU on top so you can access it with a probe. What kind of test equipment do you have?

Dave

The OSI machines should definitely be easy to replicate. Like you said, you could definitely cut down the parts where multiple identical parts were used because of small scale (memory). The video is mostly a bunch of counters and some logic, and a shift register. If you're not against using an FPGA ...

Can you post a link?

Thanks for sharing your site. I've linked to it on the main page. I am very interested in the Mittendorf board, as I had hacked a high-res mod for the 540 board, basically a 16K RAM board which multiplexed the 540 board video timing divider chain outputs with the address lines, and the data lines co...