COMBEL CPU CLOCK 16/8 (Falcon)

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Rustynutt
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COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

Let me see if I can word this right.

The COMBEL CPU clock can be set via software to output either a 16MHz or 8MHz CPU clock.

Got that.

Using the diagnostic cartridge, there is an option to change the CPU clock between the same, as well as have the Blitter clock either same as the CPU, or 8MHz.

Assuming at boot, the COMBEL is running the Blitter internally at 16MHz, and the CPU the same.

On the COMBEL, pin 192 is shown as the 8MHz CPU clock. However, that's not physically tied to the CPU clock input. The schematic just shows it "stubbed out" so to speak.

Is the only way to force the COMBEL to output 8MHz to the CPU by software, or is pin 192 pulled HI or Low some way to change state?

Make sense?
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by czietz »

You must be misreading the schematic. Of course, CPUCLK (pin 191) is connected and is shown as such.
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

Ok, 3am post, up at 8am with coffee :)

Yes , but I'm talking COMBEL PIN 192 8MHz output.

How does the COMBEL send 8MHz clock to 68030?

Or does the 8MHz software setting not actually change the CPU (normal) 16MHz clock, but only the COMBEL treats the BUS (and Blitter) as 8MHz?

I'm chasing if the Falcon can be booted at "8 MHz".
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by mpattonm »

Rustynutt wrote: Sat May 15, 2021 5:28 pm How does the COMBEL send 8MHz clock to 68030?
As Chrisitan says, it is via CPUCLK (pin 191).
Rustynutt wrote: Sat May 15, 2021 5:28 pm Yes , but I'm talking COMBEL PIN 192 8MHz output.
Which is unconnected on Falcon.
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

mpattonm wrote: Sat May 15, 2021 5:37 pm
Rustynutt wrote: Sat May 15, 2021 5:28 pm How does the COMBEL send 8MHz clock to 68030?
As Chrisitan says, it is via CPUCLK (pin 191).
Rustynutt wrote: Sat May 15, 2021 5:28 pm Yes , but I'm talking COMBEL PIN 192 8MHz output.
Which is unconnected on Falcon.
Thank you ("stubbed out") :)

So, when setting the CPU to 8MHz via CPX, the COMBEL is not actually changing the frequency to the CPU?

Apologies, don't have a scope to look at this my self.
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by czietz »

Rustynutt wrote: Sat May 15, 2021 5:48 pm
So, when setting the CPU to 8MHz via CPX, the COMBEL is not actually changing the frequency to the CPU?
Of course it is. Pin 191 as we're telling you...
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

Ok, it's all internal to the COMBEL.

Is there a way to keep the COMBEL clock at 8mhz from power on, until it reaches the desktop?
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by czietz »

Rustynutt wrote: Sat May 15, 2021 6:44 pm Is there a way to keep the COMBEL clock at 8mhz from power on, until it reaches the desktop?
Only by patching TOS (or by modifying EmuTOS). Both switch to 16 MHz early during boot.
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

Yes, next step. Playing now :)

Why?
Nemesis has lots of wires.
Games are of no importance for this machine.
Fast single clock is clean option.
Run 500KHz backwards via expansion, cut small trace from COMBEL, no hacking ACIA pins.
This board test well at 50/25MHz (diagnostics).
But to get past Blitter is a bitch at boot. That's why Nemesis, Phantom, ect.
EmuTOS will be a good test OS, but a lot of work for me to understand how to best configure for Afterburner. EmuTOS can be compiled to boot to command line. Something else to learn.
Possibly from there, launch AB Tool Kit....????
Why not just use AB and Tool kit normally? This AB has 68060.
Now mainly get all stable, step by step.
Surely have to ring DML at some point.

FPU and SDMA CPUCLK trace question (if you read this far).
I use separate wire to SDMA CLKIN from Buffer.
The trace is cut just behind this point.
When overclocking the FPU, the long trace to the (old) SDMA clock is just open.
Will this length affect attenuation of the new FPU clock (maybe like an antenna)?
Dislike pulling the FPU CLK pin up from the PLCC socket. Rater feed it from R221.

Always appreciate advice and help :)
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

czietz wrote: Sat May 15, 2021 9:53 pm
Rustynutt wrote: Sat May 15, 2021 6:44 pm Is there a way to keep the COMBEL clock at 8mhz from power on, until it reaches the desktop?
Only by patching TOS (or by modifying EmuTOS). Both switch to 16 MHz early during boot.
After successfully programming EmuTos into a Falcon ROM, managed to boot test with a 50MHz main oscillator.

This discards the idea of trying to switch to 1/2 clock at boot. :)

EmuTos boots fine, and as long as Blitter is not enabled from the desktop the Falcon is very stable.

NVDI is no longer necessary either.

Is it that EmuTOS does not use the Blitter during boot as TOS does to display the Atari logo?

Or, does EmuTos "disabled" in some way?

I don't know how the Blitter inside the COMBEL works. If always active until used, or can be disabled?

Ideas of patching Falcon TOS, and placing the patched version back onto EPROM without Blitter being used?

Would this be a difficult patch?

The Atari "splash" screen is of no importance to replace for this purpose.

Realize this is a very specific request.
Moving on to the Afterburner and testing a 68040 to 68060 socket adapter on the Afterburner, this remains a stumbling block.
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Atari030 »

That would be perfect for the CT2, damned blitter is a PITA.
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by mfro »

Rustynutt wrote: Tue Jun 08, 2021 6:43 pm ... Is it that EmuTOS does not use the Blitter during boot as TOS does to display the Atari logo?

Or, does EmuTos "disabled" in some way?

I don't know how the Blitter inside the COMBEL works. If always active until used, or can be disabled?...
There is no way to somehow "disable" the blitter. It's either there or not. You can only instruct the OS to use or not to use it and you (obviously) can do that only if the OS has alternative routines to draw using the CPU instead. EmuTOS does have this alternative code path, TOS4 hasn't (and yes, EmuTOS doesn't use the blitter until the desktop comes up and the blitter menu is found tickmarked).

The only way to enforce CPU based drawing with TOS4 (besides coding an OS patch) is NVDI.
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

Thanks for that explanation.

What I need is to not have TOS use the Blitter at boot.

From what I understand, it's how the Atari logo is drawn on the screen.

If TOS could be patched there, can get over the boot hump.

Only reason I mentioned NVDI wasn't necessary as with EmuTos can control the Blitter enable from the desktop.

Do have a grasp with how NVDI works, and what it replaces.

Never boot without it :)
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by mfro »

Rustynutt wrote: Wed Jun 09, 2021 8:18 am What I need is to not have TOS use the Blitter at boot.

From what I understand, it's how the Atari logo is drawn on the screen.

If TOS could be patched there, can get over the boot hump.
...
Not sure if that would be enough - if you have an auto folder program before NVDI generating console output, this would likely access the blitter as well.
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

You mean in TOS, or before NVDI in the actual auto folder?

The only program output to console before NVDI would be the disk driver AFAIK.
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Badwolf »

Rustynutt wrote: Wed Jun 09, 2021 4:42 pm You mean in TOS, or before NVDI in the actual auto folder?

The only program output to console before NVDI would be the disk driver AFAIK.
AFAIK, yes. The Atari logo (and possibly memory test) is blitted to screen so I don't think it's possible to avoid any blitter use with an AUTO folder. Should possible with a cartridge, though.

Patching TOS to not show the logo or do the memory test should be doable but if you go the whole hog and patch it with software blitter routines instead, I'd be very interested for DFB1.

Cheers,

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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

Sent emails out to the 2 best qualified people on the planet to do so :)

Warning, another long winded comment :)

One I know already has an excellent patch program. It's just if he has the time and initiative to modify it to "hunt and kill" inside the TOS binary.

Also thought about the memory test this morning after coffee.

Being how we now can easily reprogram TOS ROM, and that most accelerators like Nemesis back in the day just switched clocks after boot, and NVDI loaded to get around this, makes sense to get rid of this nasty problem.

With respect to EmuTOS, it works sort of ok on the Falcon.
Spent a good 8 hours with it last night.

Haven't made comments to the bug report as it seems a bit dated, and they may very well already know of them.

The kicker for me (aside from not being able to use programs like Rainbow Multimedia) was the Brainstorm JPG Decoder. The autofolder program doesn't recognize the machine as a Falcon.

Think it goes deeper than that though, Apex Media must use similar routines to load a JPG within it's environment, and also fails to load a JPG.
Apex hums happily along however with morphing routines and such, as well as when the JPG files are converted to TGA, having no issues with them.

There's also some glitchy stuff within Apex's resolution modes. 640*400 TC works fine. When trying the same, 8 bit depth, it's menus fail.

Kind of off topic, but maybe this will make sense to someone that understands these things.

On the audio side, DSP MOD players I tried worked fine, most only failing due to not recognizing the hardware, then terminating.

Other than that, EmuTOS works great.
With progress, there would be no reason to use 4.04 for my purpose as EmuTOS is supposed to work well with the 68060.

This will also be a MiNT/NOVA ATI machine, so the Apex stuff is moot.
But nice to know.

Don't understand exactly what they mean about how it works with the 68040. Think it's only been proved under emulation. JoEven has ran it on his Afterburner some time ago, so it will indeed run.
Want to start testing with the 040 first, then install the 68060 so as to not miss anything.

It's tempting to just try it, but there's the AB Tool Kit that "could" also be an issue setting up the board.

Thanks for the tutorial with programming the EPROM.
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Badwolf »

Have a go with this.

It's a custom build of EmuTOS with the following options:-

* US language (guessing that's what you want from your profile)
* Version set to 4.04 (might help with some of the apps not recognising you're on a Falcon)
* Blitter disabled
* DSP enabled
* Initial information screen always shown (useful for debugging, I find)

There's an IMG and a PRG version included.

BW
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by joska »

Rustynutt wrote: Wed Jun 09, 2021 10:41 pm Don't understand exactly what they mean about how it works with the 68040. Think it's only been proved under emulation. Jo Even has ran it on his Afterburner some time ago, so it will indeed run.
040-support is really for Aranym, not real hardware. I had a look at it some time ago and it looks like it only needs some tweaking to work on the AB. I will eventually attempt to do this, but hopefully someone else will beat me to it :D
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

Badwolf wrote: Thu Jun 10, 2021 9:11 am Have a go with this.

It's a custom build of EmuTOS with the following options:-

* US language (guessing that's what you want from your profile)
* Version set to 4.04 (might help with some of the apps not recognising you're on a Falcon)
* Blitter disabled
* DSP enabled
* Initial information screen always shown (useful for debugging, I find)

There's an IMG and a PRG version included.

BW
Thank you :)
I'll flash this in a bit.

One thing I'd forgot to mention, is it possible to exclude the EmuTos HDD driver in a build?

Noticed running HD Driver after boot, one of the drives became unreadable.
Kobold also didn't like what it saw. It "could" of been SDMA buffer issues as I've not focused on this yet, however where Kobold failed, EmuTos built in driver did copy files over from SCSI to IDE. Only using standard clock accessing SCSI. Machine is not known to of had issues in the past (but it IS a Falcon :) ).
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

joska wrote: Thu Jun 10, 2021 9:50 am
Rustynutt wrote: Wed Jun 09, 2021 10:41 pm Don't understand exactly what they mean about how it works with the 68040. Think it's only been proved under emulation. Jo Even has ran it on his Afterburner some time ago, so it will indeed run.
040-support is really for Aranym, not real hardware. I had a look at it some time ago and it looks like it only needs some tweaking to work on the AB. I will eventually attempt to do this, but hopefully someone else will beat me to it :D
Thank you, didn't know how to word what I'd gathered from the teams compatibility chart :)
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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Badwolf »

Rustynutt wrote: Thu Jun 10, 2021 3:24 pm One thing I'd forgot to mention, is it possible to exclude the EmuTos HDD driver in a build?

Noticed running HD Driver after boot, one of the drives became unreadable.
I can't see an obvious way to disable it, sorry. You can turn off IDE support, but I don't know if that stops all IDE access working.

You shouldn't run HDDriver under EmuTOS. That'd be like running ADHI after HDDriver.

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Re: COMBEL CPU CLOCK 16/8 (Falcon)

Post by Rustynutt »

Just caught this :)
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