OSI 600D Superboard Build

[HigashiJun]

[stephen_usher]

From eBay, but they are usually pretty quick. Maybe tomorrow.

Do you not have a tracking number from the seller?

[rubber_jonnie]

From eBay, but they are usually pretty quick. Maybe tomorrow.

Do you not have a tracking number from the seller?

Annoyingly, no.

I've used this particular seller many times before as I've found them to be reliable and selling good parts, so it's odd that they have been slow this time. Delivery is supposed to be between 24th-27th of Jan according to eBay, but they are almost never accurate and it's never taken this long for this seller to get something to me.

Not much to be done until they arrive, but at least the rest of the RAM arrived already.

[rubber_jonnie]

Well, the ICs and a bunch of others arrived. And it's better, but it still isn't booting.

I have 1Mhz at pin 37, PHI 0, and both PHI 1 & 2 are both showing clocks out. All good.

The video output shows 15.63Khz, but there is nothing on screen.

PXL_20240125_120304933~2.jpg (237.69 KiB) Viewed 836 times

/RESET at the CPU is going high, but /HALT is stuck low, and is even low with the CPU removed, so I'll look at that next. EDIT: There is no /HALT, I was looking at the pinout, that is for the Atari Sally only.

It's progress as at least there are clocks now

[stephen_usher]

Yeah, clock and video (even if it's blank) is a good sign. Any activity on the address and data buses?

[rubber_jonnie]

Yeah, clock and video (even if it's blank) is a good sign. Any activity on the address and data buses?

Not had a proper look at it yet, lunchtime ran out and busy with work now. Going to try and have a look later this evening.

I also got sidetracked by looking at /HALT being low, but later realised I was looking at the pinout for an Atari Sally, so it was a wild goose chase.

[rubber_jonnie]

Yeah, clock and video (even if it's blank) is a good sign. Any activity on the address and data buses?

OK, so in short, there is data on the address and data buses - at certain times.

If I do a reset by hitting the break key, I see address and data bus activity at the CPU, ROMs and RAM, though not for long, so it looks like it is trying to do something.

I have printed out all of the tests from the build guide and need to walk through them one by one (Again) to be 100% sure all the tests are good and I didn't miss something.

Then I want to work back through the schematic to look at the video circuit and be sure I haven't missed anything there. Clearly I'm getting 15.63KHz, which is good, but there's no data being sent out.

I did get the occasional brief flash on screen, but it was too quick to see if it was anything interesting. Also, hitting break repeatedly does sometimes cause the address lines to get busy and stay busy, though still no image.

[stephen_usher]

Well, it's trying to do something at least.

P.S. Do you have a ROM listing with comments? I wonder if the code is starting, trying to initialise something and then waiting for a response which it's not getting.

This was the gotcha on the Mac IIci I had.

[rubber_jonnie]

Well, it's trying to do something at least.

P.S. Do you have a ROM listing with comments? I wonder if the code is starting, trying to initialise something and then waiting for a response which it's not getting.

This was the gotcha on the Mac IIci I had.

I don't unfortunately, but it does feel like it's trying and then failing that's for sure.

[rubber_jonnie]

OK, so the suggestion from over at OSIWeb is that without any ROMs fitted, so basic etc, there should be garbage on screen and there isn't, so I'll definitely focus on the video circuitry next, and there are some good pointers in the service manual, which has oscilloscope readings and colour coding for the video circuit on the schematic to help make it easier.

I am still going to run through all of the basic tests from the assembly manual too.