exxos's Atari, Amiga & retro forum

Thought I would start a new post for this. Will the PCB work for the H4? Just wondering if I should finish building one to start testing the H4?

@kodak80 - I had started this mod a while back but have too many projects on the go to debug.

I jumpered R913 so that I could isolate the on-board oscillator and plug the mod board in. It is easier on the H4 to tap into the jumper bank to feed the right chips etc the new clock signals.

Picture of R913 jumpered with resistor on a jumper socket and shrink wrap.

I designed a new one ages ago, but no time to test and no H4 to test even.

@Icky With R913 as a jumper, we can feed the 32mhz CLK signal into the Mod board rather than have the OSC on the Mod board itself which would mean that for future PCB mods the 16mhz Mod board could be made smaller by removing the on-board OSC.

exxos wrote: 22 Feb 2020 00:37 I designed a new one ages ago, but no time to test and no H4 to test even.

If you want the new design PCB testing, I would be happy to get some created and tested but I can probably start with the current one and as suggested, feed 32mhz CLK to it from the H4 OSC.

kodak80 wrote: 22 Feb 2020 00:41 If you want the new design PCB testing, I would be happy to get some created and tested but I can probably start with the current one and as suggested, feed 32mhz CLK to it from the H4 OSC.

Its one of those things I need to sort out myself, its totally untested and likely need a lot of tweaking... like the previous mod, takes a lot of trial and error to get the thing even half working.


EDIT:

In theory the old mod should work like on the Alpha, but I suspect it will need a lot of messing about... plus there is the "1 in 4 chance" of it atually booting because of the random clock skew (which I hope might be better on the new board) . So if you want to try and get the current board work, have fun ;)

Spent some time today looking at starting this on one of my H4 boards.

I have built one the 16mhz mod boards and tested the clock output on this is as expected with the 32mhz OSC on the mod board.
https://www.exxosforum.co.uk/forum/downl ... hp?id=6796

First thing I have found is that the jumper pins on the board do not match the schematic image, in that the pins may be the opposite way round on the board.

Image removed to stop confusion. See image in next post

Hi @kodak80, yes the pins dont match the schematic as layout usually always different to the schematic.

There are a few pins not quite right in your picture. I am just updating an image with the correct pin layout for you.

Lifted directly from the board layout. Slight spelling mistake on DE_MM should be DE_MMU.

Thanks @Icky image is easier to read than mine.

Updates copy here:
Will look to connect things up tomorrow. :D