exxos's Atari, Amiga & retro forum

After a long day and running into multiple issues (it wouldn’t be me otherwise), we have a working H5CB.
If you forget the dead shifter, the dead MMU, and a non-collaborative CPU it was finally not too difficult to get it running :D Next steps:
- test the Waveblaster
- modify a Sony drive to enjoy HD floppies
- Install a 16 MHz booster or a ST536… Enough for today anyway.

:bravo: :2k2: :girldance:

Think this makes 3 new H5s built now :)

Over the weekend I was burning some ROMs for the H5 and again forgot to byte swap the images thus losing some precious EPROM.
Most of the products here (H5, Dual TOS, ST536) uses a 16 bit PLCC EPROM which is convenient in terms of space, but requires byte swapping.
I was wondering why the byte swap can’t be done at hardware level : connecting D0–D7 from the EPROM to D8-D15 of the bus and D8-D15 of the EPROM to D0-D7 of the Bus? It would avoid byte swap of the ROM or did I miss something ?

The 68000 uses big-endian byte order. This means it stores the high byte (most significant byte) at the lower address in memory.

I can't remember the format of the ROM images online but maybe they are actually wrong byte order hence the need for swapping.

But also depends on if your programmer is using big-endian little-endian byte order. Basically one is swapped Vs the other one..

I'm just sticking to convention on how it's supposed to be wired up. In this case, fix the software ;)

It takes like 5 seconds to flip the order... Use EPROMS if unsure so you can easily change if mistakes are made.

Hopefully I'll get flashy clock finished at some point so everyone can have flash ROM on the H5. Won't need to bother with ROMs at all then.

And a second H5C up and running. Working fine but it’s mute…
I will troubleshoot the audio circuit later, I suspect the mixer chip didn’t like being unsoldered and resoldered using hot air. The one on the other H5 survived, but maybe this one was weaker or I took too much time.

:bravo: :girldance:

Honestly, with most of the components and sockets already installed, this is pretty easy to build.

olivier.jan wrote: 02 May 2025 11:17 Honestly, with most of the components and sockets already installed, this is pretty easy to build.

Yeah. I tried to make it as simple as possible. I think anyone should be able to get one up and running within 1-2 hours.

Ok, actually audio from YM is working fine although a bit noisy.
The S2 Waveblaster is not outputting any sound though ( it works fine on the other H5). I will need to go through the schematics to trace the issue.

On a different note, what is the purpose of the two pads located between ROM and GLUE ?

olivier.jan wrote: 02 May 2025 17:55 On a different note, what is the purpose of the two pads located between ROM and GLUE ?

You'll have to take a image as not sure which ones your referring to...

EDIT:

You mean this jumper ?


That's always been there.. Its to split DE or something when bus speeders were being experimented with. Really it needs to be removed these days.. Its jumped by a track anyway..