I recently purchased a MegaST 4 from eBay. I knew that there was something going on with it since one picture (https://photos.app.goo.gl/HpC8QAfjWPAasnGi9) indicated a modified TOS. Lo and behold, I had no idea how much of a Frankenstein I had bought.
Here are some images: https://photos.app.goo.gl/AP8FH6VrRaNfeFwL8
My hardware knowledge is limited but here are my preliminary findings:
- This Mega (well, the CPU clock) is being accelerated, possibly up to 16 MHz according to the GEMBench Integer Division Benchmark results. Not by some fancy board but by a homebrew kit, possible along the lines of the instructions given in this article (https://www.stcarchiv.de/stc1992/09_gehtdoch.php)
- For reasons I can not explain the RTC battery has been refactored into a makeshift battery pack. Well, at least it did not leak.
- As expected the machine features custom ROM EPROMs to deal with the higher clock speed
Originally I planned to do a recap and fit some nice board giving me TOS 2.06 and IDE support (i.e. MonSTer or Storm/Lightning ST).
I'll definitely hold on to a recap, but I don't want to keep the makeshift accelerator as-is. So either I'll get rid of it, or I'll rebuild it. But I'm concerned that it wouldn't play nicely with a MonSTer or Storm/Lightning ST.
Since the speed gain from the existing kit is minimal at best (i.e. RAM access is still at 8 MHz) I have a small preference towards getting the board back into a stock state, but I might be missing some parts (GALs, oscillator?).
Your advice on the best path forward with this machine would be highly appreciated.