exxos's Atari, Amiga & retro forum

Dear Steve!

Steve wrote: 25 Jun 2022 10:19 I downloaded your 12mhz zip file, I am very intrigued but I don't speak any German. Do you have an English translation available?

Oh, sorry. This is a very old project. So it isn't available in English.

Also, does running the motherboard at 12mhz greatly benefit speed and benchmarks, I assume it would be very good! Is it stable?

Yes, indeed. My mainboard works since many years with 12,5 MHz (50 MHz oscillator) very stable. And you have got 150 % more speed in any cases.

Best regards
Robert

Dear BigSteve!

BigSteve wrote: 25 Jun 2022 15:08 As a fellow newbie that will be playing with Mhz shortly.... why 12Mhz and not 16? Some constraints I am going to run into...?

The MMU and GLUE are developed in a time, where is suitable to fix the timing between the signals with a greater delay like today. So the signals drifted away, if you increase the mainboard clock. Above 12,5 MHz most of the both custom chips from Atari doesn't work really good together, because some signals overtake other signals inside the both chips. It depends in great order from the right choose of this both chips. It isn't really stable above 12,5 MHz.

Best regards
Robert

Hi!

DoG wrote: 25 Jun 2022 16:44

BigSteve wrote: 25 Jun 2022 15:08 As a fellow newbie that will be playing with Mhz shortly.... why 12Mhz and not 16?

I haven't read the document so I don't know for sure, but I think it's the bus speed he is changing?

Yes! I do so. But it isn't easy to do this. Perhaps if you got a look into the document, you will see, that six signals and clock lines must be separated on the mainboard and new signals must be installed for video (2 MHz, 0.5 MHz, HSYNC, VSYNC, DE and Blank). Some signals should be added to the the pcb.

Best regards
Robert

Gruess, Robert!

BW