- The LaST Upgrade -
PART 29 - Falcon CT60 RSO OSC
Last updated September 13, 2016
This prototype module is almost like the CTCM but this is programmed with a simple resistor instead. I had no end of trouble with CTCM when I overclocked and couldn't easily revert back to default speeds. I mostly just changed the IC and it worked at 60mhz, but after a while it stopped working altogether so I gave up with it.
My CT60 is also VERY fickle about what fixed OSC it uses. I only ever found 1 brand of 66mhz osc which worked. Other brands didn't. I stood no chance of getting 90mhz speeds working despite trying various brands & speeds of osc. In the end I got frustrated enough to design my own clock module.
Designing this module was a lot of trail and error and sometimes it would work and sometimes not, I was starting to question my own sanity towards the end of the work. Anything from the voltage output, so the "loading" of the signal, the DC offset voltage between the clock module and the CT60 clock distributor IC, it all added up into a huge mess of chaos. So my board compensates for clock issues and has a onboard filter to keep the clock line stable. This took a lot of trial and error, but this clock module solves all the clock problems I have found so far with the CT60.
My module uses a RSO (Resistor set oscillator) which is capable of running from around 60-160MHz. The preset trimmer is a multiturn (22 turns) 20K type. This gives very fine control over the MHz speed. Simply turn the trimmer one way for higher speed, and the other direction for lower speeds. Pressing reset on the falcon will reboot and CT60 will show the MHz speed at the top of the screen. So you know what speed you are running at. Should you clock to high and falcon no longer boots, no problem! just turn the pot a couple turns back and downclock to a lower speed.
Once the top speed is realised (note you need a genuine REV6 E41J 060 CPU to run near 100MHz speeds! They should be available in my webstore tried and tested) The 2 small pads can be measured on a multimeter on resistance to measure the resistance value of the trimmer. Once known, a 0805 SMT resistor can be used instead of the trimmer resistor. The image on the left shows the timmer in place, the image on the right shows without trimmer and with fixed resistor. SMT values are plentiful, but if the exact value is not obtainable then the closest higher value should be used.