exxos's Atari, Amiga & retro forum

You seem to have more caps on the clock lines then there should be ?

The clocks are extremely ropey if I don't have them as I posted earlier.

PhilC wrote: 01 Jul 2019 18:20 The clocks are extremely ropey if I don't have them as I posted earlier.

Understand that.. but you can't add caps onto any other lines.. it only takes a tiny bit to de-sync the clocks enough to cause it to malfunction. You have to build it *exactly* as I built it else it won't work.

Ok will remove them and try again later.

Last night I had it all set up without the extra caps.

The board would never boot but I was getting a 50mhz screen and the cpu wasnt halted.

There also seemed to be plenty of activity of the rom lines. Do we have a minimum recommended speed for the TOS roms whilst running at 16mhz?

100ns for 16mhz should be OK.

Ok cool, the rom is an 85ns.

Whoop whoop!

My Alpha now boots to desktop in 16mhz mode 8-)

Although it's about as stable as a jelly in an earthquake.

To get it to boot I've had to do the following:

Remove 68ohm resistor from the pcb.
1) Fit a 5k pot to each of the 16, 8 and 2mhz lines. In all honesty a 500ohm would likely do but I don't have any.
2) Put your scope leads on the 32 and 16mhz lines and if you have a 4 channel, (I dont) put it on the 8 and 2 as well.
3) Start with the pot on the 16mhz line. Line up the leading edge of the waveform with the 32mhz one.
4) Do the same with the 8mhz compared against your now calibrated 16mhz line.
5) and finally do the same for the 2mhz using the 8mhz line as the guide.

Now I still need to do the 2mhz line but mine now boots to desktop, although it usually bombs out after accessing the menu bar but now at least I know the chips I have are more or less 16mhz compatible.

I need to measure the pots and then fit fixed value resistors when I get a mo.

Once stable tomorrow I'll postpone Gembench results etc.

:bravo:

Sounds like a issue with the glitter, also note I ended up with less than 1k pull up on dtack. I forget the values, think it was more like 700r.

exxos wrote: 02 Jul 2019 23:36 :bravo:

Sounds like a issue with the glitter, also note I ended up with less than 1k pull up on dtack. I forget the values, think it was more like 700r.

Where did you put it on dtack?