http://www.spacious-mind.com/html/tu..._540_plus.html

Untested:

Oh, and the too fast chess clock, keep the IRQ at 4mhz/0x4000 to correct it. (but it won't be same as a real Turbostar 540 then!)
It's a really lazy overclock modification that they didn't bother to correct the timing.

From where do you know that the clock on this Turbostar 540+ is running too fast (i.e. that they didn't change the clock timer or the ROM)?

IMHO changing both the CPU and the IRQ freqency at the same factor wouldn't make any sense, would it?
Such an overclocked device would play exactly the same moves and games as the normal device, just everything at a higher speed - it's just as if you would increase the emulation speed in MAME by the same rate (5.53/4), so I don't think it's useful to add this 'real' model 540.

IRQ timer is from the same XTAL as the main CPU clock. For correct timing, they would either have to have 2 XTALs, or a ROM modification.

Here's where I saw the mention of the timing difference: https://tinyurl.com/y3k3jfpg
"By the way, when using the 540+, be sure to set the ‘B’ time limits for 25% to 38% longer
than you really want, as the time limits have not been re-programmed for the faster speed."

Ok, then it's indeed not necessary to add this 540+ as an extra model - if anyone wants it, then he can just as well change the emulation speed to 138%.

Hello,

Surprise!

Just before I knew Achim was going to send me his Constellation 3.6 for reverse engineering, I started bidding on a broken unit on eBay... with the intention of studying it and performing romdump for MAME. Since I don't like to withdraw from the auctions even I didn't want this computer anymore, I was finally the winner, and I received it yesterday afternoon.

https://www.ebay.de/itm/174002199372

It was worth it! Because it has a very different ROM.

Achim's unit
s/n: 362168
Q.C.Passed label: 1/85
ROM reference: 831A 6133-8316
ROM header: (c)1982Kittinger

This unit
s/n: 366966
Q.C.Passed label: 4/86
ROM reference: 854-501
ROM header: (c)1985Kittinger

The PCB references are the same.

Sending right now to hap and Franz the romdump.

There are still many surprises to discover with these little computers!

Regards,
Gerardo

Miniaturansicht angehängter Grafiken

 

Hello Gerardo,

this could very well be the same as Quattro. Tibono has a Constellation 3.6 with a Quattro ROM inside.

https://www.schachcomputer.info/foru...ead.php?t=5732

Hello,

Yes... Confirmed also by Franz, and I just compared the romdumps.

I'm sorry... sometimes I focus too much on the hardware, and don't read or pay enough attention to what others have investigated previously.

Regards,
Gerardo

Well done! I feel less alone with my odd 3.6/Quattro. My data is exactly the same, serial number apart:
Tibono's unit
s/n: 366649
Q.C.Passed label: 4/86
ROM reference: 854-501

Grüße,
Eric

Frage: Did the Mark V have a French version? The machine can be set to French language (by placing diodes) and that works fine on emulation. When I google around, I can only find German and English versions.

I assume the German market was big enough to make a local release, but France not as much.
If there is a French version, are there any photos of the button labels?