Philips VG-8235 unknown ROM modification

Door wiggs1979

Supporter (3)

afbeelding van wiggs1979

28-04-2022, 14:48

Hello, my first time posting here and still relatively new to MSX machines. I grew up on ZX Spectrums.

I've recently purchased my first MSX2 machine, a French Philips VG-8235 (VG8235/19), which apart from the drive belt having disintegrated, it seems to be in working order. I had plans to replace the internal drive with a modern alternative and do the upgrade to support 720k disks.

However, upon opening the machine, I've noticed it's already had an upgrade of sorts, but I'm not sure what it's doing. There's a 27512 ROM piggy-backed on another ROM where the disk ROM would usually live, as well as a couple of logic chips, 74LS138 and a 74LS175 piggy-backed. Then of course a nest of wires! Would anyone know what it could be? I could desolder the ROMs and read them out, but I wondered if it might be some known modification? Is there anything I could do to interrogate the ROMs perhaps from the machine itself?

A photo of the modification.

Many thanks. :)

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Van wiggs1979

Supporter (3)

afbeelding van wiggs1979

28-04-2022, 16:51

I've just stumbled across the linked PDF file, it seems to be a modification for internal MSX-DOS 2.

MSX-DOS 2 in Philips VG 8235/00

Van Manuel

Ascended (18781)

afbeelding van Manuel

28-04-2022, 18:25

Do you see the MSX start up with Disk Basic version 2.0?

Van wiggs1979

Supporter (3)

afbeelding van wiggs1979

12-05-2022, 21:33

Manuel wrote:

Do you see the MSX start up with Disk Basic version 2.0?

If I understand the modification correctly, it'll only boot to MSX-DOS if I put in a suitable floppy disk too, else it just boots to BASIC. At the moment the floppy drive doesn't work due to needing a new drive belt, I could rig up a GoTek to test though.

Van Manuel

Ascended (18781)

afbeelding van Manuel

12-05-2022, 22:04

If the MSX-DOS 2 ROM is built in, it will boot into Disk BASIC 2.x. That's what I asked and you can check that already.