Or you could clock another 74 by write (or two) to the PSG that then ungates the clock, no need for an extra MCU. Reset of that 74 would be controlled by ISA reset or a simple RC time constant.

Yeah but DTK Floppy BIOS and other Option Rom`s seem to access the Port Adress of PSG and activate it.
Also EPSON IM BIOS trys to access 0C0.
So i needed a more flexible solution.
I tried with a flip flop before which worked fine on 2c0 but never on 0c0.

And ISA Reset is only active on hard reset, but not within a soft reset (STRG+ALT+DEL)
I already use it to retrigger the MCU.

Aha ok, so MCU will be only foolproof solution.

Found a new issue, when i cut the clock off from sn76489 - floppy bios hangs until the clock is attached back to sn76489
then it continues to boot.
This is only a issue on AT Computers. As 0C0 is unsupported because Second DMA Controller is using this Address.
Using 1E0 or 2C0h this is no issue at all.

You have to gate the Ready signal too then, it is controlled by the clock and will cause infinite bus cycle if there's no clock.

it must be something else, if i bend the ready pin up, it also occurs.
no time anymore 🙁 for further investigations.
Tomorrow work.. so i have to wait until sunday.

EDIT:
deleted.

Thanks again 😀
that did the Job, the SN76489 was defective i replaced it and now it works by gating clock and ready.

That's good news ~

only gating the two brings problems 😒
i need to fully cut the sn76489 from bus then.

That makes no sense, there's no read function on the chip that I know of, the inputs are all actual inputs according to silicon shots...

yeah i know that, also does make no sense to me. i need to hookup my oscilloscope to see whats happening here..
everything is wired correctly, i triple checked it.

EDIT:
simple things may prevent from success..
just add the damn capacitor 😉

So finally i got it working, was bit challenging,
a pull up is required on SN76489.

i also did not add a capacitor which caused various symptoms,
i thought for a short test it will suffice.
Also breadboard has loose contacts, i throw it away..

i had a real huge series of mistake.
so i throw all away and started over again.

Damn it works ! 😀

Not bad for a Bakermen 😉

matze79 wrote:

So finally i got it working, was bit challenging, a pull up is required on SN76489. […]
Show full quote

So finally i got it working, was bit challenging,
a pull up is required on SN76489.

i also did not add a capacitor which caused various symptoms,
i thought for a short test it will suffice.
Also breadboard has loose contacts, i throw it away..

i had a real huge series of mistake.
so i throw all away and started over again.

Damn it works ! 😀

Not bad for a Bakermen 😉

Great news, congratulations ! 😀

matze79 wrote:

Not bad for a Bakermen 😉

Hmmm…

https://youtu.be/ymdssZOAx3Q

all is tested, i rerouted changes and order pcb 😀

Oho, a proper prototype ! Very nice ~

Yeah its better to verify every change to ensure it will work as i wanted 😀

Current progress:

silkscreens needs some clean up.
LM386 needs to be turned to match other ICs.

i`m testing Decoder for 0x205 now.
for IBM PS/1 3 Voice Support.

Good news, got next boards, now i verify all changes 😀

Then we go one Stop further.
Bracklets!

New Driver for Port Redirection without need of QEMM386 or EMM386 is in development.

matze79 wrote:

New Driver for Port Redirection without need of QEMM386 or EMM386 is in development.

Nice !