Extended resolutions

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Reylan
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Extended resolutions

Post by Reylan »

Hello,
I have a ct60e. I'm already using centscreen to have 1024x768. I'm feeding a 50 MHz clock to the videl.
I would like to go further.
How can I clock my bus to 50 MHz ? I know that it was possible with the ct60
Thanks
V
sety
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Re: Extended resolutions

Post by sety »

You could populate the bus speeder on the ct60e. The CT63 schematics from Radolphe's website should help you find what components you need to add.

The only thing that makes this a bit tricky is that the ct60e's PCB design is a bit more modern and there is coper infill everywhere. The whole PCB is a massive heat sink so the THT stuff (which is really just the pins for connecting the ribbon connector and the jumpers) can be a bit of a challenge with home soldering tools.
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mikro
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Re: Extended resolutions

Post by mikro »

Much easier is to go with a separate bus accelerator like Phantom. @Steve from Exxos Forum has had a great success with it.

Also, you can't clock *bus* to 50 MHz, 25 (from originally 16) MHz is the maximum sane value.
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Re: Extended resolutions

Post by DarkLord »

Don't forget you can "over" clock the Videl and DSP as well.

Up to 50mhz, IIRC. Although I couldn't get mine above 40
without it getting flaky - same with the CT60, never could
get above 100mhz (95 max) without errors.

I so wanted to bust that 100mhz barrier... :)
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Re: Extended resolutions

Post by TXG/MNX »

mikro wrote: Mon Dec 27, 2021 3:39 pm Much easier is to go with a separate bus accelerator like Phantom. @Steve from Exxos Forum has had a great success with it.

Also, you can't clock *bus* to 50 MHz, 25 (from originally 16) MHz is the maximum sane value.
Phantom is not for sale anymore is it ? Or are there people that still build these ?
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Re: Extended resolutions

Post by Rustynutt »

Arg, guess nobody believes the modification I've went on and on about. Only a ROM, oscillator and keyboard patch required.
No need to mess with wires to the VIDEL.
Reylan
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Re: Extended resolutions

Post by Reylan »

Rustynutt wrote: Wed Jan 26, 2022 8:20 pm Arg, guess nobody believes the modification I've went on and on about. Only a ROM, oscillator and keyboard patch required.
No need to mess with wires to the VIDEL.
Did you document it a some point ? Link ?
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Re: Extended resolutions

Post by Rustynutt »

It's buried in a few different threads here.

First question, what type of clock patch does the Falcon have?

I "think" one of the main reasons some of the speeders that provide clock switching did so because of issues with the Falcon Blitter at boot. It's used to draw the Atari Logo on screen. Above 20MHz bus, the blitter will crash.

What a few others on the board did to help was show how to edit a ROM image so the Falcon can boot with an oscillator faster than 40MHz.

With the Falcon bus configuration bit changed to keep the blitter speed 1/2 CPU clock, the Falcon will boot with a 50MHz oscillator installed, the blitter only running at 12MHz then.

A 25MHz BUS gets the VIDEL up to speed where 640*400(480?) TC mode is available, and quite speedy at that.

As far as the ROM mod and CT60, the CT uses its own TOS onboard to boot from, so the edited ROM file only comes into play when booting in "030" mode. The BUS remains running at the speed of the oscillator installed. I've tested 62MHz, there the VIDEL begins to display a lot of screen artifacts. 55MHz seemed to be the optimal speed, but 50MHz likely the smart choice as you can get everything possible out of the VIDEL there using your screen enhancer.

The only "patch" one has to do is provide a 500KHz keyboard clock as described in the Nenesis or Phanton docs.

You'll need likely the latest Exxos buffer board installed.

A modified TOS ROM

A socket to install alternate oscillators. I'm in the US, that's easy, just remove the oscillator, install a socket to use.

A 500KHz oscillator, or bread board with ripple counter and maybe your old 32MHz clock and divide it down. Installation per Nemesis/Phantom docs.

Unless you need to actually change clock speed, this route makes for a relatively clean way to mod the Falcon.

Make sense? ( not often I do :) )
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Re: Extended resolutions

Post by mikro »

Rustynutt wrote: Thu Jan 27, 2022 6:26 amAbove 20MHz bus, the blitter will crash.

What a few others on the board did to help was show how to edit a ROM image so the Falcon can boot with an oscillator faster than 40MHz.

With the Falcon bus configuration bit changed to keep the blitter speed 1/2 CPU clock, the Falcon will boot with a 50MHz oscillator installed, the blitter only running at 12MHz then.
I really wouldn't say this is generic truth. CT2, Nemesis, Phantom, ... all of them have proved that none of this is really needed. Some Falcons may be more sensitive than others but generally speaking all you need is a well-tweaked bus accelerator from the mentioned list.

So TL;DR version is, get yourself a Phantom which gives you 25 MHz bus and 50 MHz Videl. Stormy can give your more details, he built his own own one from scratch.
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Re: Extended resolutions

Post by stormy »

Hi there, I didn't build the Phantom - but I did build a phantom-clock-patch from scratch using mikro's schematics. The Phantom itself I purchased from Tuxie @ the Thunderstorm team. Try emailing them at Thunderstorm@tuxie.de perhaps they might have some left. These days you don't need to build a clockpatch from scratch either, the Exxos clock patch is built on the Phantoms 'delay' mechanism and works perfectly, I've tested it. I don't know about Centuriontech's clock patch, but if you email him he might tell you if it supports bus accelerators.
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Re: Extended resolutions

Post by Rustynutt »

mikro wrote: Thu Jan 27, 2022 6:36 am
Rustynutt wrote: Thu Jan 27, 2022 6:26 amAbove 20MHz bus, the blitter will crash.

What a few others on the board did to help was show how to edit a ROM image so the Falcon can boot with an oscillator faster than 40MHz.

With the Falcon bus configuration bit changed to keep the blitter speed 1/2 CPU clock, the Falcon will boot with a 50MHz oscillator installed, the blitter only running at 12MHz then.
I really wouldn't say this is generic truth. CT2, Nemesis, Phantom, ... all of them have proved that none of this is really needed. Some Falcons may be more sensitive than others but generally speaking all you need is a well-tweaked bus accelerator from the mentioned list.

So TL;DR version is, get yourself a Phantom which gives you 25 MHz bus and 50 MHz Videl. Stormy can give your more details, he built his own own one from scratch.
You can't boot a Falcon at anything over 40 MHz is all I'm saying. And unless one needs to revert to a slower clock, it's just more hardware to include.
Editing the ROM is so much more simpler.

Personally would never go back to a Nemesis or Phantom type accelerator, but that's me.
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Re: Extended resolutions

Post by Rustynutt »

Exxos patch provides the extra flip flop on the DMA, like the Phantom.
Centuriontech buffer is a much more elegant install, but does not do this. It also does not terminate the COMBEL clock with a value resistor on the flip flop buffer as the Exxos does. It has 0 ohm resistors. It's more intended for a CT installation, providing a point to tie in the CT which have the circuit for bus accelerating on board. The CT63.
The CT already buffers the bus clock, and if one goes back through Rodolphs post, it can be read a clock patch isn't necessary.
Finally, scratching his head, he said go ahead and leave a patch installed if that what it takes.
As Badwolf mentions, there is around 16ns to play with at stock bus speed communicating with the COMBEL.
I'm not good at math, when kicking that up to a 25MHz bus, that windows narrows.
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