Questions to the H5 C1 - russellnash

[russellnash]

I have been messing about with by board for the first time in weeks. I am aware that there are audio fixes to be done, but is it normal that as it comes unmodified that the only sound I get is just loud noise, rather like someone is digging up the road with one of those pneumatic hammers?
The other thing is I have put the 16mhz booster on the board. I have read the guide but some things are unclear to me so I need to ask some questions as someone who has no idea whatsoever.
In the guide you see an adapter with a CPU on it, but I am assuming that you can mount the board on a 5V Bus IO port and it will work with the PLCC CPU that is already there. Is that correct?
ROM_CS wire - H4/5 right pin of JP13. I haven't seen a Jumper marked with that number, I am guessing it is the one with Glue and ROM CE on it? I am using TOS 1.4, do I need to connect CE to the right pin of that jumper (ROM CE)? That would mean that the jumper wouldn't be linked together i.e. use glue ROM decoding? Or do I not connect CE and leave the glue ROM decoding jumper closed? Maybe there are other things I need to do too.

[coonsgm]

The audio I experienced before making the mods, sounds similar to what you are describing.

Regarding the 16mhz booster / decoder. You need to connect to the right hand pin on the Glue Decoding jumper marked as ROM CE. That enabled me to boot to TOS 2.06 just fine.

For 16mhz you need to do the following:

• Not have the two jumper pads on the decoder connected (default)
  Connect Pin 39 from the Shifter IC to the 16mhz signal on the booster
  A 16mhz capable CPU mounted on top of the booster / decoder

In my case I have done all this but am experiencing instability. I get occasional graphical glitching and bombing out. I am getting the 16mhz speed though when run in Gembench.

I've tested two marked 16mhz CPUs that both function mostly. I've also tested a known 16mhz 68k CPU from another accelerator board. All have experienced some amount of instability. Love some thoughts / feedback on that. Here are some photos of my board with the decoder booster along with GEMbench CPU results.

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[coonsgm]

Just resolved the stability issues by swapping the Shifter chip. Not sure exactly why that is the case, but different Shifter = completely stable now.

[russellnash]

Thank you very much. I thought this board would be good opportunity try a booster because you don't have to take out the CPU and risk damaging the very delicate board. We will see. :)

[exxos]

Clock signals need to be soldered really. A slight bit of a bad connection and it's game over.

I have seen some shifters with "bad" 16mhz clocks. They were very problematical on the original 1.44 floppy mod kits which is why I ultimately gave up for a dedicated osc.

But generally it can help to place something like 68R in series with the 16mhz wire. Also keep wires a short as possible.

[coonsgm]

Previously I had soldered the shortest wire possible to the old shifter which didn’t help.

I still have that wire and will be soldering it 😁

[russellnash]

I have been looking again at the reset circuit that is always stuck in reset. The pull up measurement to pin 18 of the CPU measures at 483R, which is coincidentally approximately half of what it is supposed to be i.e. 1K. When that happens it makes me wonder if it is caused by two resistors being in parallel. Can anyone confirm that it isn't, or at least shouldn't be, two 1K resistors in parallel, only a single one giving a pull up resistance of 1K?

phoenixpullups.PNG

[exxos]

I think you need to back up a bit here first. It's unclear if your trying to debug with the booster fitted or not. No idea if you have all the correct jumpers in place, in particular flashy clock jumper. No idea what ROM you have or jumper settings. No idea what mods have or haven't been done such as the osc resistor fix..you should be checking voltages on pins not resistances as you could get false readings with silicon in circuit. For sure try to get the stock configuration working before anything else and post clear images of your board.

[russellnash]

The reset circuit hasn't worked yet as per this thread. It is with the PLCC CPU and no booster.

[russellnash]

I have tried it out and the value of the pull up resistor whether 1K or 500R doesn't have any effect on the reset circuit.
I am using TOS 1.4 with the recommended jumper settings as listed in the thread about jumper settings. The reset pin is only ever between 0V when you press the switch and 1.4V. The flashy clock jumper provides 5V to Halt but has no effect on Reset.