Recent content by petteri

Recap was simple, no broken traces or issues with pads. Boots up, happy mac and floppy drive works. As I have really limited space for projects, this goes either to a Finnish auction site or EU ebay.

Someone wanted to give away faulty IIcx (not starting at all) and Apple Color High Resolution RGB Monitor. As it was nearby I decided to help him. IIcx has clean and nice plastics, Macintosh II Video Card, 4MB RAM and disk drive. HDD was removed but the original sled was left there. Some cap...

Yea, a socket would be a good idea but my intention was to keep this as original as possible. And I felt my desoldering skills are not good enough...

Stable enough to run tests, I wouldn't use that for production use. Another important reason for me not to swap the crystal oscillator was to keep this IIfx as original as possible (collectable, driven only on Sundays...) and I didn't want to risk with soldering oscillator several times.

Good point! I reverted back to original and tested floppy drive. Everything fine. I don't have anything using serial so cannot test that. I think I'll let this be for a while. Unless there is really cold winter weather coming up and I could do a overclocking test in freezing conditions :-D

I went through some junk computers I had and placed heat sinks on MCU and CPU. I also placed a random 12V fan to blow some air over them and memory. First I reached 57.4MHZ (115MHz on the Si5351) and that seemed to be stable. So I tried 60MHz but that barely booted on the happy mac icon...

55MHz and seems to be stable, at least to run performance tests. I managed to make it boot at at 57.4Mhz but that was not stable enough to run tests. Maybe some additional cooling for CPU, FPU and memory controller would help? I replaced the breadboard with a perforated protoboard. I also...

And to shock those who have some idea of electronics: 🤖

Alright, some progress finally. I used 5V from SCSI power connector to trigger an external interrupt on Arduino (https://www.arduino.cc/reference/en/language/functions/external-interrupts/attachinterrupt/) and that then starts the clock signal at the desired frequency. Still using breadboard and...

I managed to get stable operation with 100MHz crystal oscillator, random wires, breadboard etc as seen here: https://68kmla.org/bb/index.php?threads/macintosh-iifx-with-pronitron-80-21-v1-5.42667/#post-467388 So I guess there is some tolerance for stupidity but with limits 🙃 I think the clock...

I don't have frequency counter but I used my RTL-SDR v3 tuned to 100MHz (or 80MHz) and I could see a spike in the waterfall display when Si5351 was powered and set to the corresponding frequency. There is no 5V or 12V available on the IIfx power supply before startup? My current plan is to...

I made some more experiments: 1. Ground the disable pin on the original setup and open it after pressing the start button. No happy chime. So the clock signal should be available right at the start. 2. Have the Si5351 and 74HCT125N running on a battery (common ground) before starting up. No...

I have been experimenting with Si5351 and SN74AHCT125N. The idea was to use Si5351 to generate clock signal and then use SN74AHCT125N to change its level more suitable to 5V circuit. "The Si5351 is a versatile I2C programmable clock generator that is ideally suited for replacing crystals...

Around two years ago I was asking some programming related questions https://68kmla.org/bb/index.php?threads/getting-started-with-application-development-for-system-6-7.36470/ My goal was to create a little CTF (capture the flag) challenge for a hacking event. I am not sure if the challenge was...

50MHz (100MHz oscillator) works fine, I have 70ns RAM. https://68kmla.org/bb/index.php?threads/macintosh-iifx-with-pronitron-80-21-v1-5.42667/#post-467388