exxos's Atari, Amiga & retro forum

Maximilian wrote: 07 Mar 2019 22:56 P.s. witch 68030 did you get? 33c? , that could probably run on 50Mhz...., just remove the coprocessor if it is slower than 50Mhz

It's a 40 MHz 030, but I'm looking for a 25 MHz one. I don't think I'll want to run this card much faster. If/when I get this to work it's going to be sold at a charity auction, and the 40 MHz CPU is to be used in a TF534 :)

Maximilian wrote: 07 Mar 2019 22:56 If you have to wait for parts i have an Idea... :twisted:
1. Take the 50Mhz 5v Oscillator and test it on 3v, if it runs you are in luck and you can use it on 3,3v.
2. Put the above on a piece of perfboard with frequency divider using a d-flip flop on 3,3v , and then you have 25Mhz.
(don't forget a 19Uf cap across VCC and GND)
3. Test

4. Put on your new Oscillator on when it arrives.

My thought with the 5V oscillator was to get the levels higher as the buffer seems to react better to the 7 MHz clock than the output from the 3.3V oscillator. I might be able to create a simple level shifter instead... But as you can see in my earlier post the output from the 3.3V oscillator looks quite ok now. But not after the buffer.

I think I'm going to check at what level the buffer triggers with a variable supply. Something weird is going on.

terriblefire wrote: 08 Mar 2019 07:26 There is a resistor pad in the Rev 3 for this purpose. North of the RaM cpld next to the SPI port.

I’d also recommend putting the FPU in if you haven’t already. It has the same effect

I'll see if I have a suitable resistor, but I might only have ones with larger footprints at the moment. I could test with FPU, but I don't think this card will have one when it's done as I only have 40 MHz FPUs that I was going to use for the 534.

25mhz FPUs run fine at 50Mhz. I don’t think anyone made a 50Mhz fpu

terriblefire wrote: 08 Mar 2019 10:16 25mhz FPUs run fine at 50Mhz. I don’t think anyone made a 50Mhz fpu

I only have three FPUs (40 MHz), and I was thinking that I would use them together with the 40 MHz CPUs for the TF534 cards. For testing, absolutely, but the plan was to run the TF530 at 25 MHz. But plans do change :)

I’ve had several Tf530s not work until the FPU is inserted. It damps the clock line.

terriblefire wrote: 08 Mar 2019 10:32 I’ve had several Tf530s not work until the FPU is inserted. It damps the clock line.

And it looks nice with 7 MHz only because the frequency is lower?

Thanks for taking your time answering my noobish questions, btw :)

kludge wrote: 08 Mar 2019 10:38 And it looks nice with 7 MHz only because the frequency is lower?

Yeah. I did a Tf53x board dedicated to finding reflections. I patched up things manually and took measurements all over the place. The 530 needs all its components on to work realistically. That was the assessment

Isn’t she lovely? At least she’s booting diagrom now, albeit with some weird results occasionally. :)

WHEN diagrom is able to start all my memory and IRQs check out. Unfortunately every other time it doesn’t boot. The same with KS 1.3/3.1.4. It yellow screens almost every time, but I’ve been able to boot almost into workbench (on floppy) on both of them.

I suppose it’s a clock issue. Running a 5V 50 MHz oscillator now just for testing. I’ll order a new 3.3V 25 MHz oscillator and new clock buffer and we’ll see how it behaves then.

Or if I’m able to amplify the 3.3V clock somehow with what I have laying in the basement I might have a try at that.

terriblefire wrote: 08 Mar 2019 07:26 There is a resistor pad in the Rev 3 for this purpose. North of the RaM cpld next to the SPI port.

What's a recommended value for RCLKLOAD?