09479: lb186: Unable to boot a floppy disk

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
09479	Media Support	Major	Always	7 days ago	22 hours ago

Tester	Robbbert	View Status	Public	Platform	MAME (Self-compiled)
Assigned To	AJR	Resolution	Fixed	OS	Windows (x64)
Status [?]	Resolved			Driver	ampro/lb186.cpp
Version	0.288	Fixed in Version	0.289GIT	Build	x64
		Fixed in Git Commit	fd9727d	Github Pull Request #

Summary	09479: lb186: Unable to boot a floppy disk
Description	This system is marked as working. According to the manual, the system waits for a boot disk and will then boot without requiring further intervention. There's no software list, so I tried my only LB186 disk and it didn't boot. The system is also supposed to be able to use standard IBMPC boot disks, so I tried a number of them, without luck.
Steps To Reproduce	>mame lb186 -flop1 e:\data\pc\ok\freedos360k_1_20061014.img Cursor flashes faster but nothing else happens. In the debugger, nothing is loaded into memory, and code execution stays in the BIOS. Tried a bunch of pc disks, MAME rejected most of them, however 360k ones were accepted, but none did anything.
Additional Information	Tested in 0.277, the system works there, able to boot one disk "freedos360k_1_20061014.img". Seems quite picky; other disks that work in pc's get the "Non-system disk or disk error" response instead. In 0.288, there's no messages, doesn't seem to read the disk at all.
Github Commit

Flags	Regression
Regression Version
Affected Sets / Systems	lb186

Attached Files

No.24418 AJR Developer 22 hours ago edited on: 21 hours ago	The problem has to do with the timeout loop at FC825 expiring before the FDC's restore command even spins up the disk. I've hacked around it by extending the timeout. It could be due to MAME's 80186 being somewhat imprecise about instruction timings (particularly not emulating the prefetch queue), and slight differences can easily accumulate over tight loops like this.