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#Macspice oyunu driver#
#Macspice oyunu code#

Each 74LVC245 has a 0.1 uF ceramic bypass capacitor about 2 mm from its VCC pin. Three of the chips are configured for unidirectional signals like the address bus and control signals, and the fourth is bidirectional for the 8-bit data bus. A set of four 74LVC245 chips provide 5V to 3.3V level translation. The FPGA runs at 3.3V, powered from a Micrel MIC5504-3.3YM5-TR LDO regulator. Some hardware background: shown above is a simplified schematic of the card (click for a hi-res version). From this I concluded that the crash is happening during execution of the Yellowstone ROM code, rather than the Yellowstone card somehow causing an error with another card or with the Apple II itself. I measured times of 0.19ms, 1.57ms, and 28.5ms. During a boot-up where the computer crashes, this ROM access lasts a much shorter random-seeming amount of time.

#Macspice oyunu code#

During a normal boot, there’s a 93ms period of near-continuous Yellowstone ROM access, which is probably running the ROM code to look for an attached drive. With a logic analyzer, I examined the pattern of card accesses during good and bad power-up sequences.

#Macspice oyunu driver#

More cards means more capacitance on the data bus: maybe the Yellowstone output driver wasn’t able to switch the bus signals fast enough? More cards also means more load on the data bus: maybe the Yellowstone output driver wasn’t able to source or sink enough current to maintain a valid logic high or low voltage?

in the Apple IIgs, crashes were more likely to occur as the number of other cards increasedīased on this, I suspected some kind of electrical problem as opposed to a logic design problem.

the crash occurred in an Apple IIe and an Apple IIgs.

the crash occurred even when no disk drives were attached – so it’s unrelated to the drive or the disk contents.

it didn’t matter what slots the cards were in.

it didn’t matter what the other cards were.

With more investigation, I gathered these clues: With another card present, the computer would crash into the system monitor during power-up about 90% of the time. Success! But the excitement was short-lived: it only worked when Yellowstone was the only card installed in the Apple IIe. With Yellowstone configured to clone a Liron disk controller, I was able to boot from a Unidisk 3.5 drive as well as from a Floppy Emu in Smartport emulation mode. This story begins 12 days ago, the first time I successfully booted my Apple II using the Yellowstone card.

Those nice clean zeroes and ones are gone, and instead I’m struggling with voltages, logic thresholds, capacitance, and power in an attempt to explain what’s going wrong. That’s the story of my Yellowstone FPGA-based disk controller for Apple II, and it’s slowly driving me crazy. The digital abstraction of zeroes and ones is lovely, but electronics debugging often requires a deeper look into the realm of analog signals.

Gregg Lemke on Yellowstone Universal Disk Controller for Apple II.

Hightray on Floppy Emu Disk Emulator for Apple II, Macintosh, and Lisa.

Steve on Floppy Emu Disk Emulator for Apple II, Macintosh, and Lisa.

John Payson on NMOS 6502 Phantom Reads, Odd Yellowstone Bugs.

Jeffg on The Amazing Disk II Controller Card.

Yellowstone Universal Disk Controller for Apple II Floppy Emu Disk Emulator for vintage Apple II, Macintosh, and Lisa