philips vg8235

Paragon (1150)

02-09-2005, 16:50

there is a problem with my msx, a philips vg8235,
It boots and sais it has 256 kb memory,
though all games (konamis megaroms) for 256 kb don´t work.
Anyone knows whats wrong with this msx????

and next to that, ive been searching like hell for konamis megaroms for 128kb computers, but am also not able to find them......

the only game I could find for 128kb was spacemanbow, but this is without sound,

By Mafcase

Champion (258)

03-09-2005, 00:25

Is it really a problem??

For you in this case it will... But I don't think your computer is broken or something like that, I'm afraid you're the 'proud' owner of a version 00 computer. I'm not sure what the exact difference is, but IIRC the memory mapper in your comp is different then in the regular 8235 series.

(on the bottom of the machine there is a grey sticker which tells you more about the computer, a serial number etc. On this sticker you can also find if it is indeed a '00' version)

By SKiLLa

Expert (121)

03-09-2005, 01:01

I believe Repair-Bas can fix that for you norakomi ... BIOS flush !

By HansO

Paladin (672)

03-09-2005, 08:55

The memory mapper in the VG8235/00 has a hardware bug which makes the second part of the mapper unaccessable.

Easy to fix by placing a 1 nF capacitor between pin 7-U23 and 8-23 (GND).

This is an official Philips fix as described in the service manual: look at my website http://www.hansotten.com - MSX Info - MSX Hardware - Philips VG8235/00/02/19 service manual - last page of the pdf

By norakomi

Paragon (1150)

04-09-2005, 12:13

hey its a vg8235/20 !!!!

is that good news?

By wolf_

Ambassador_ (10135)

04-09-2005, 12:50

uhm.. perhaps it's really not relevant.. but perhaps your 256kb refers to 128kb mainram and 128kb vram ? This is what you'll find on the casing of the machine.. (at least on my 8245 and 8250) ..

By HansO

Paladin (672)

04-09-2005, 13:03

hey its a vg8235/20 !!!!

is that good news?
It is not. Those versions do not have a memory mapper hardware bug.

Do you want to load from disks those Konami roms? Cant do with a 128Kb RAM mapper.

As Wolf already indicated: 256K RAM as mentioned on the case means 128Kb RAM for the cpu as a memory mapper and 128Kb as videoram for the v9938 video display processor.
Thats why memory upgrades to at least 256Kb were and still are popular since nearly all MSX 2 machines came with 128Kb RAM

Are you seeing at boot time that there is 256Kb RAM? Or does it say 128Kb RAM and 128K video RAM? In the last case you have a wellfunctioning standard VG8235 incapable of running those cracked Konami ROMS.

If you are a bit experienced: many articles describe how to upgrade memory ram, not a complicated job. An external memory mapper is another option.

By BiFi

Enlighted (4348)

04-09-2005, 13:13

Usually you need to have more user RAM than the megarom game to be able to run it... Though there are megarom game (cracks) which do work with 128 kB user RAM... Those games are usually MSX1 games (or MSX2 games which require 64 kB VRAM) and use VRAM for storage as well. The game does play slower then as the game switches banks all the time... and VRAM access to copy data from (or to) isn't that fast.

and about all non-japanese MSX2 machines came with 128 kB user RAM... All japanese MSX2 machines have 64 kB user RAM.