02845: sflush: [possible] CPU clock speed may be too high, judging by info in pcbinfo file.

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
02845	Original Reference	Minor	Have not tried	Jan 18, 2009, 23:28	Feb 19, 2011, 20:19

Tester	chowell	View Status	Public	Platform	MAMEUI
Assigned To		Resolution	Open	OS
Status [?]	Acknowledged			Driver	midw8080/8080bw.cpp
Version	0.129	Fixed in Version		Build	Normal
		Fixed in Git Commit		Github Pull Request #

Summary	02845: sflush: [possible] CPU clock speed may be too high, judging by info in pcbinfo file.
Description	The MACHINE_DRIVER entry for sflush specifies the CPU as: MDRV_CPU_REPLACE("main",M6800,2000000) /* ?? */ indicating a Motorola 6800 running at 2 MHz. However, the MAWS pcbinfo file for sflush: http://www.mameworld.net/maws/pcbinfo/Sflush.txt which describes the PCB from which the ROMs were dumped, says: Taito original board set with Motorola 68A00 CPU. The Motorola 68A00 was only rated for 1.5 MHz maximum. 2 MHz speed would require a 68B00. Unfortunately I have no board or schematic to double-check the processor clock. Keep in mind that the 6800 used a different clocking scheme from the 8080, so their clock speeds are not equivalent. A memory access on the 6800 took only 1 clock cycle, while it took 3 clock cycles on the 8080. Since 8-bit microprocessors were mostly limited by memory access, even a 1 MHz 6800 should provide at least as much processing power as a 2 MHz 8080. I suppose the following MAME bugs may be related to this clock speed issue: http://mametesters.org/view.php?id=1603 http://mametesters.org/view.php?id=821
Steps To Reproduce
Additional Information
Github Commit

Flags	Possible
Regression Version
Affected Sets / Systems	sflush

Attached Files

No.03606 chowell Developer Jan 19, 2009, 00:05	Has anyone considered comparing this game to Field Goal (fgoal), another Taito game produced at about the same time? fgoal has its own driver, and judging by the sources there are some similarities between it and sflush. (There are also differences, of course.) For comparison, fgoal's pcbinfo info file: http://www.mameworld.net/maws/pcbinfo/Fgoal.txt says the board also had a 68A00, while the fgoal driver has a CPU clock of 1.0065 MHz (10.065 MHz / 10). Also, there is a manual available for Field Goal with schematics, which might prove useful for comparison: http://www.arcadedocs.com/vidmanuals/F/FieldGoal.pdf That manual also specifies a 68A00 and a 10.065 MHz clock crystal.
No.07241 hap Developer Feb 19, 2011, 20:18	Ok, it's changed to 1.5mhz for 141u3. It still needs to be verified though, as well as other possible similarities between sflush and fgoal.

No.03606

chowell

Developer

Jan 19, 2009, 00:05

Has anyone considered comparing this game to Field Goal (fgoal), another Taito game produced at about the same time? fgoal has its own driver, and judging by the sources there are some similarities between it and sflush. (There are also differences, of course.) For comparison, fgoal's pcbinfo info file:

http://www.mameworld.net/maws/pcbinfo/Fgoal.txt

says the board also had a 68A00, while the fgoal driver has a CPU clock of 1.0065 MHz (10.065 MHz / 10).

Also, there is a manual available for Field Goal with schematics, which might prove useful for comparison:

http://www.arcadedocs.com/vidmanuals/F/FieldGoal.pdf

That manual also specifies a 68A00 and a 10.065 MHz clock crystal.

No.07241

hap

Developer

Feb 19, 2011, 20:18

Ok, it's changed to 1.5mhz for 141u3.
It still needs to be verified though, as well as other possible similarities between sflush and fgoal.