Centurbo 1 evolution 3b -> CT60 booster

[foft]

4596EFD4-71AE-4D58-872E-B5ED8E6F79E9.jpeg

This says to replace U44 and U68 with the new ones provided. One has two pins lifted with extra connections to be soldered to the other. So they look to be modified.

I guess I’m not 100% sure though he did provide new ones with it. Perhaps with a faster spec. Though if unchanged it’d be odd to need a new wire between them.

It is about 30 years now, possibly forgotten:)

[foft]

On the booting without NVRAM sub-thread. I accidentally disconnected a wire from my battery when installing the CT60. When I first started it I had these symptoms:
I) 030 mode, no display
Ii) 060 mode, hangs on colourful CT60 screen
So it didn’t boot in either mode, until I started the diagnostic cart which fixes up the NVRAM.

I also noticed that changing NVRAM settings in the 1.05 boot menu is unreliable. It works fine from the CPX though!

[Steve]

On the booting without NVRAM sub-thread. I accidentally disconnected a wire from my battery when installing the CT60. When I first started it I had these symptoms:
I) 030 mode, no display
Ii) 060 mode, hangs on colourful CT60 screen
So it didn’t boot in either mode, until I started the diagnostic cart which fixes up the NVRAM.

I also noticed that changing NVRAM settings in the 1.05 boot menu is unreliable. It works fine from the CPX though!

foft, can you actually get boot delay to work? I'm using 1.05 and no matter what I set it to, it just ignores it each time.

[foft]

foft, can you actually get boot delay to work? I'm using 1.05 and no matter what I set it to, it just ignores it each time.

Well I can change the number of seconds, but it doesn't do anything...

[Rustynutt]

On the booting without NVRAM sub-thread. I accidentally disconnected a wire from my battery when installing the CT60. When I first started it I had these symptoms:
I) 030 mode, no display
Ii) 060 mode, hangs on colourful CT60 screen
So it didn’t boot in either mode, until I started the diagnostic cart which fixes up the NVRAM.

I also noticed that changing NVRAM settings in the 1.05 boot menu is unreliable. It works fine from the CPX though!

What was the bus clock? (see my note above).
The CT "may" hang if in boot 1.05 isn't set to not use NVRAM. Didn't test that condition

[foft]

What was the bus clock? (see my note above).
The CT "may" hang if in boot 1.05 isn't set to not use NVRAM. Didn't test that condition

It was set to use NVRAM I think. I think that is the default and this is before I had it booting.
The bus clock was tried at 16MHz (ie default) and then 25MHz (CT boost).

[Rustynutt]

What was the bus clock? (see my note above).
The CT "may" hang if in boot 1.05 isn't set to not use NVRAM. Didn't test that condition

It was set to use NVRAM I think. I think that is the default and this is before I had it booting.
The bus clock was tried at 16MHz (ie default) and then 25MHz (CT boost).

If using CT Boot 1.05, you can set it in the boot menu to ignore NVRAM. Think that's the setting which allows booting without an actual NVRAM in the socket.

Your mileage may vary, I ditched the CPX in favor of using the 1.05 boot menu. To me, the most useful feature was controlling the CTCM on 2 boards, and as forgetful as I am, would have the CPX setting to high or low rebooting/powering down :) The other has a fixed oscillator.

The CPX does allow the same setting to ignore (may not be the exact nomenclature) NVRAM.

To do this in "Falcon mode", at least what I've discovered, is you will need at least a 48MHz COMBEL oscillator to boot without the NVRAM in place. Again, don't know why. Keep in mind, you'll also need to edit and burn a TOS EPROM as the "stock" ROM image won't allow a Falcon to boot with an installed oscillator of 48MHz. The Falcon bus control register bit needs to be changed to keep Blitter at 1/2 CPU clock to boot at that speed.

This may not be worth your while honestly, only discovered this stuff experimenting with maximum COMBEL clocks.

If SV equipped, I'd say it's of no value at all
But for a stock Falcon, or CT only install, the faster bus clock allows for a reasonable performing VGA TC mode.
On my machine, 46MHz COMBEL will allow VGA TC, with glitches. Ideally, 48-50 seems to be the magic speed, with 60MHz upping bandwidth quite a bit looking at benchmarks.

[foft]

On a similar subject, I decided to add the unpopulated booster circuit to match to my CT63.

Boost/CPU	030	060
Off	working	working
On	working	black screen

This seems slightly odd since the booster circuit clearly works just fine (since the Falcon boosts fine in 030 mode). However the CT63 doesn't like it.

Note that I know the booster is disabled by default in 030 mode, I enabled it by tying F030 boost high and double checked its enabled with the scope and gembench.

I noticed a few changes on the CT60 (which works boosted in 060 mode):
i) R32 -> 0ohm (to DSP clock)
ii) An additional resistor on pin 1 of the quad buffer 74HC125D.
I've replaced the 33ohm with 0ohm (dsp clock), with no change.

Ho hum!

[foft]

I thought I'd try another of the "mandatory fixes" on the Falcon board to see if they help.

So I replaced the data and address pull up resistor arrays with 2.2K. That is P7,P11 (data bus) and P8,P13,P17 (address bus). This didn't really help, but it sounds like a worthwhile change anyway if its less likely to blow up the ST-RAM (see viewtopic.php?p=93025#p93025).

[Steve]

I thought I'd try another of the "mandatory fixes" on the Falcon board to see if they help.

So I replaced the data and address pull up resistor arrays with 2.2K. That is P7,P11 (data bus) and P8,P13,P17 (address bus). This didn't really help, but it sounds like a worthwhile change anyway if its less likely to blow up the ST-RAM (see viewtopic.php?p=93025#p93025).

Hey foft, if it's convenient for you could you take some photos of your board and highlight the bus resistors in question? It's just that this hasn't been highlighted or done by anyone else yet (for a falcon) and it'd be nice to have some visuals on the matter. Thx.