Hello everyone!

I have to ask about this picture:
https://www.schach-computer.info/wik...-Mainboard.jpg

The rightmost chip is marked as GAL but all models of this type that I saw have about 14-22pins while this one has 64 and it looks more like a HITACHI H8 or some kind of... Also these special functions of TurboKing as storing user's games / opening lines cant be handle with installed ordinar ROMs / RAMs, if I understand this stuff correctly.
So Im very confused what is the type of this chip? The information is required for tuning because currently it allows only 6Mhz to run - with higher frequency quartz it doesnt want to work (faster EPROMS already set)...

Thanks in advance!

The CPU evidently is a 6502 ("R65C02P4") and you should be glad that it runs at 6 MHz. Most of them run just at 5 MHz. Usually this CPU can't get tuned.

If you want to tune the board, the first item should be changing the CPU. Try a modern WDC CPU that might run at 10 MHz or higher. You can get it from Mouser's, USA or Mouser, Munich, Germany.

Walter

Hi, of course I forgot to mention that CPU was replaced by W65C02S8P-10 Mhz. But I also have to say that my Modena was tuned from 4 to 8 Mhz with old R65C02P4 and it keep working perfectly! So the problem lies in this strange chip.

Ok, so this chip seems to be a UPD78310 microcontroller by NEC, but the strange thing is that its datasheet says it supports frequency up to 12Mhz...

Hi, the linked picture shows two RAM chips, which seem to have an access time of 120 ns. Probably this is to slow to work with 10 MHz properly...

The Corona has 2 similar chips labelled as "NEC 8817 KX (C) SCISYS". As a lot of 74... logic ICs found in other 65C02 chess systems are missing, I guess this is a custom chip manufactured by NEC for SCISYS which incorporates all of the missing logic chips. The Corona comes with a W65C02-8 (MHz) CPU and a 5 or 6 MHz quartz. It can easily be tuned to 8 MHz just by changing the quartz.

So I doubt that the custom chip is the reason for your tuning problems. Note that the pinout of the W65C02 is not fully compatible with the R65C02, so you cannot simply put the W65C02 into an R65C02 socket.

Furthermore, the W65C02-10 (MHz) ist doubtful. I bought 10 of these in China. It turned out they had the same pinout as the R65C02 and were no faster than 5 MHz. Some did not work at all.