Overclocking X68000 computers

[Cyothevile]

Recently I have made small PCB to overclock my PRO and it's stable. It also appears similar to the circuit is used in ACE clock-up. Pro is currently clocked at 15mhz with XVI ROMs for stability. I removed one of the FG screws and added a switch in the back.

Benefits to overclocking your PC is simply to get more out of it and maybe those slowdowns will be less annoying. It should still be noted most software just require 10mhz model. Some computers require 5mhz oscillator to also clock-up DMAC which was included in my kits I just sold. The option to solder 5mhz oscillator to PCB and run wire for DMAC is there. However for non-PRO models this could be troublesome since DMAC I believe is on IO boards. I don't own super, ACE and base model to confirm.

I have clock-up information for the PRO, Compact and XVI.

I don't have the clock-up information for the other models.

Would someone be able to post/share it to confirm a few suspicions I have?

If I post this PCB to GitHub and it works as I suspect... Where the PCB can be used for everything except XVI, compact and 030...I want to leave precise instructions for people.

[hoshikawa]

you are clearly misinformed about some or all of this... the DMA controller, a hitachi HD63450, is rated for and uses a 10mhz clock. it lives next to the 68000 CPU in all models. why you would try to feed it 5mhz is beyond my reasoning. it can be overclocked to a point (14-15mhz) and symptoms of failure due to overclock are floppy read/write failures and fm audio glitching. there are command line tools that specifically test an overclocked DMAC that I use when I work on machines I sell. the SCC (serial controller) is a sharp LH8530a, a clone of the zilog z80 DART. it uses a 5mhz clock generated by the Sicilian chip. It lives on the bottom board, symptoms of failure due to overclock are keyboard and mouse input not responding.

[hoshikawa]

https://gamesx.com/wiki/doku.php?id=x68000:converting_x68000_compact_to_red_zone talk about reinventing the wheel

[Cyothevile]

Perhaps Dmac is incorrect term. I think it is serial controller. Idk. I'm not opening my PRO again to verify. That's too much effort. Sorry for slinging the wrong term.

Also your link doesn't have schematic. Not sure how this is reinventing.

[Cyothevile]

I'll verify and install it inside my compact first. Red zone conversion. Very certain it can be used for normal XVI

http://imgur.com/a/Zwq1ssS

[hoshikawa]

your link doesn't have schematic. Not sure how this is reinventing.

[EDIT - This Imgur URL leads to an image of the PCB with components denoted in line art, in lieu of a full schematic. - Kendrick]

https://imgur.com/a/8XOFgTb

[incrediblehark]

If you have a PCB that will work with an XVI I'd be interested in trying it with my overclock in lieu of the 6BE6AP BEEP ram module.

[Cyothevile]

If you have a PCB that will work with an XVI I'd be interested in trying it with my overclock in lieu of the 6BE6AP BEEP ram module.

If you have that RAM card just use that.

My tower XVI has that card and it has a clock of 24mhz.

[incrediblehark]

For some reason the beep card doesn't play well with my midi+ram card. I ended up removing the beep internal and use an additional ram I/O card to max out, but I'm looking for an alternative way to get my overclock working again. If you ever sell a pcb I'll buy one, I have the oscillator, switch, etc.

[Cyothevile]

For some reason the beep card doesn't play well with my midi+ram card. I ended up removing the beep internal and use an additional ram I/O card to max out, but I'm looking for an alternative way to get my overclock working again. If you ever sell a pcb I'll buy one, I have the oscillator, switch, etc.

It seems on further research the Compact and XVI use same clock-up circuit. The X68030 can be clock to 33mhz stable by just replacing the stock 50mhz crystal with 66mhz. Also requires one additional motherboard modification I'm still trying to read.

My materials arrive today for many project so I can make it.  Actually since over 349 people read this thread over 10 days and don't help but you helped you can have one for free. I just ask you take some photos of the installation.

[Cyothevile]

Over clock for Compact is safe and successful. It boots fine on 16mhz and 24mhz and ran a few games fine from SX-Window hard drive image I made.

[incrediblehark]

For some reason the beep card doesn't play well with my midi+ram card. I ended up removing the beep internal and use an additional ram I/O card to max out, but I'm looking for an alternative way to get my overclock working again. If you ever sell a pcb I'll buy one, I have the oscillator, switch, etc.

It seems on further research the Compact and XVI use same clock-up circuit. The X68030 can be clock to 33mhz stable by just replacing the stock 50mhz crystal with 66mhz. Also requires one additional motherboard modification I'm still trying to read.

My materials arrive today for many project so I can make it.  Actually since over 349 people read this thread over 10 days and don't help but you helped you can have one for free. I just ask you take some photos of the installation.

Thank you! And of course I'll try to take as detailed pics as possible.

[incrediblehark]

Just wanted to send an update,  received Cyo's overclock pcb in the mail and installed it in my XVI, and works quite well! I had some issues at first but they were unrelated to the board. After removing my RF shield per Cyo's advice all went well, and the install was super easy! Here's a pic of the points needed to install the pcb in the X68000 XVI:



Here's LHES and SI showing my speeds in 24mhz mode:




Switch fully installed and also using the FG port on the back of the PC:

[amigo-mexicano]

Sorry for the necroposting...!

Hey @Cyothevile do you still have these boards available? I'd love to overclock my PRO.

Thanks in advance!

[X-Col]

These boards are for XVI systems only.

I wouldn't mind one of them to convert my Compact XVI to Red Zone.

I did make my own overclocking board for my ACE HD and it achieves a stable overclock of 14Mhz

Update: I have just found the little schematic I drew up on Excel if you want it? Just let me know, it's very simple and easy to make

[incrediblehark]

@X-Col i would be interested in this, any side effects to overclocking the Ace to 14mhz? Graphical issues etc?

[neko68k]

Some games sound wrong because their music drivers rely on 10mhz operation. Super Hang-On comes to mind. The SCC becomes overclocked as well if you care about using the serial port. Can't remember if the mouse is impacted, might be. My keyboard works but YMMV. Also not all DMAC's are created equal and you may see instability under heavy DMA load. On my PRO its mostly ok but really heavy MXDRV/PCM8a stuff causes the DMAC to fail and it needs a reboot to come back. A few games are really superior like Geograph Seal.

[X-Col]

@X-Col i would be interested in this, any side effects to overclocking the Ace to 14mhz? Graphical issues etc?

I agree with neko68k and your mileage may vary. My ACE can be overclocked over 14Mhz (even 15/16Mhz) but then I start to experience issues related to the DMAC as explained above. The DMAC initially passes the tests on Masterdisk EX at 15Mhz but starts to fail after 20 minutes or so of usage. I get a 100% rock solid stable overclock at 14Mhz and it always passes the DMAC tests on Masterdisk EX, so I use a 56Mhz oscillator.

Here is the simple circuit I used to build mine:
https://docs.google.com/spreadsheets/d/1Ycaxa5nOlYtFxGlsp7zuXKIsH6T8WxsV/edit?usp=sharing&ouid=105316727416597213991&rtpof=true&sd=true

SW = Switch (on/off)
FB34 = cut this on motherboard and solder these wires to either side

And no, I don't get any graphical glitches, even at 16Mhz. :-)