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ID Category [?] Severity [?] Reproducibility Date Submitted Last Update
03724 Speed Trivial Always Feb 9, 2010, 21:45 Feb 10, 2010, 21:47
Tester Oliver_A View Status Public Platform
Assigned To Tafoid Resolution Fixed OS
Status [?] Resolved Driver mrdo.cpp
Version 0.136u2 Fixed in Version 0.136u3 Build
Summary 03724: mrdo: Incorrect XTALs cause for problems with refresh rate and game speed.
Description The driver for Universal's Mr. Do has the wrong speed for the CPU, sound and screen refresh rate.

Reason: the schematics have the wrong crystal oscillator values.

Mr. Do uses 2 crystals, each for the video timing, and CPU / Sound speed.

In the schematics, the crystal for the video timing is 20Mhz and for the CPU/Sound 8Mhz, which is divided by 2.

On the real Mr. Do PCB (8201 revision), the values for the video timing is 19.6 Mhz and for the CPU / sound 8.2Mhz.

That means, the real values for the game are:

CPU: Z80 clocked at 4.1 Mhz.
Sound: 2*SN76489 clocked at 4.1 Mhz.

The change in the video oscillator frequency also affects the refresh rate.
Steps To Reproduce Locate a real Mr. Do PCB and compare the oscillator frequencies with those of the schematics. On revision 8201 PCB, they will not match.
Additional Information I have included 2 photos taken from my ORIGINAL Mr. Do PCB which verify my claims.

The board was not modified in any way. In fact, it would be quite hard to purchase the two oscillators, because the frequencies are so odd.

Note: this descripancy in clock speeds is most probably also responsible for the off-key music in Mr. Do Run Run.
Flags Verified with Original
Regression Version
Affected Sets / Systems mrdo
Attached Files
zip file icon (2,191,229 bytes) Feb 9, 2010, 21:45
There are no relationship linked to this issue.
User avatar
Feb 9, 2010, 23:34
edited on: Feb 9, 2010, 23:42
I can confirm that the music sounds a bit more accurate to recordings with the new xtal values. Thanks for the fine and clear pcb picture. Reworded the description slightly.

These pictures are dated nearly 7 years ago - are they really that old?
User avatar
Feb 9, 2010, 23:48
Hi Tafoid,

no, they were taken a few minutes before I submitted the report.

The 2003 date comes from my old digi cam, which resets the date every time I recharge the batteries.

Thanks for the quick response.
User avatar
Feb 10, 2010, 20:59
edited on: Feb 10, 2010, 21:00
I'm applying this information to the driver for inclusion into MAME. Expect it to hit in 0.136u3. Another Dev was nice enough to pull his PCB out and it matches yours in model and xtals.
User avatar
Feb 10, 2010, 21:44
Great! :D

I would also try to check if the XTAL information for Mr. Do's Wild Ride, Mr. Do VS. Unicorns and Mr. Do Run Run have the same error. I read in another bug report that the sound in Mr. Do Run Run was also off, and it might be the same problem.
User avatar
Feb 10, 2010, 21:47
That was believed to be an issue with the PSG. Positive contributions are always welcome if they are from original sources and MAME seems to be in dispute. Thanks.