Phillips NMS 8250 disk boot issues

By menne386

Supporter (2)

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12-05-2019, 15:25


Since a couple of weeks i am the proud owner of a Phillips NMS 8250 with an extra disk drive installed.
The machine has collected impressive amounts of dust, so i took it apart to for some cleaning and inspecting.

I've messed something up:

Before the cleaning session BASIC or DOS disks booted without any problem.
After the cleanup, BASIC disks boot fine, but DOS disks can only booted manually by doing a "POKE &HF346,1" followed by "CALL SYSTEM" then i get my dos prompt and can call "AUTOEXEC.BAT" manually.

Anyone ever had this issue? and solve it?

My guess is an issue with the disk-rom, maybe i can dump that rom to disk to compare it to a downloaded version?


By Hans41

Expert (71)

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12-05-2019, 22:50

Hello Menne386,

When you say BASIC disks boot fine, I assume your 8250 just boots and goes into BASIC ?

When your 8250 boots without disks in any of the drives, does one of the drives show activity after both drives have shown they are active ? In other words, does one of the drives act as an A-drive ? Cause it sounds like you don´t have a drive that acts as an A-drive anymore.

Are you sure you connected the flat cables exactly like they had been connected before ?

By Manuel

Ascended (19683)

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12-05-2019, 22:50

Yeah, if you put an AUTOEXEC.BAS basic program on a disk, does it start up?
If you do FILES, do you get to see the files of drive A?

By meits

Scribe (6575)

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13-05-2019, 01:06

poke &hf346,1 does not set any other drive as A:
So if booting the computer with a disk with and msxdos.sys inserted ends up in basic and with just the poke and _system you end up in dos, you do indeed have a strange situation.

By Wild_Penguin

Hero (644)

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13-05-2019, 19:35

One guess: messed up disk boot sector?

If you format on PC, MSX usually hangs at boot (IIRC). Perhaps it could cause something else, too...

EDIT: This means of course, the issue should be floppy-specific and easily remedied by reformat.

By menne386

Supporter (2)

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14-05-2019, 13:02

Wow! thx for all the responces!

I'll try 2 answer all the questions in 1 post:

1) Discs with an "AUTOEXEC.BAS" file on it boot normally.
2) Drive activity is: A blink, B blink... wait a second, then A: blinks. (And will boot basic discs)
3) FILES command (or DIR, when i get into DOS using the trick i mentioned) correctly shows the disc content.
4) @Meits: indeed exactly as you describe, when i insert ANY of my DOS disks, and turn the system on, i end up in basic, and have to manually type "POKE &HF346,1:_system" to get into from there i have to "autoexec.bat" to have a "normal" dos disc boot. (And basic-based discs boot straight into autoexec.bas, no prob.)
5) Messed up boot sector: i have this on any dos disc, including freshly created ones.

+ 1 new symptom: when the MSX is warm after say 30 minutes of gaming, normal behaviour is restored, and dos discs boot again.

My guess is that i damaged either some of the control IC's or the drive. I tried swapping the drives (using the jumper on the drives) and i tried in single drive configuration.

One potential fix would be buying a megaflashrom cartridge... would also allow me to play rom games.

By Wierzbowsky

Guardian (3649)

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14-05-2019, 17:40

This could be the case when the RAM with the broken bit(s) is used to load the boot sector. As the result the boot sector can't boot to DOS (either crashes or tries to find a non-existing SYS file because of name corruption). Run a MEMTEST to check the RAM.