> >>Ah, the famous /20-series... Can anybody tell me the difference between
> >the
> >>VG8235 and the VG8235/20???
>
A service manual I got, indicates there are even /02 and /19 types,
apart from /00 and /20. I can't remember ever having seen a /02 or
/19 type. I'm not quite sure, but I think there is a 8235/40 as well.
>From the outside, there's no difference to be seen, other than the
type number on the bottom plate. The difference is on the inside.
>From a hardware-builders point of view, there's only 2 kinds of
Philips 8235's: 'older models' (I think that would be /00 up to /19
types), and 'new' models (that would be /20 or higher).
These older models have a relatively big motherboard, with a
relatively large number of parts on them. The circuit is put together
so clumsy in some ways, Philips ought to be ashamed to have attached
their name to it once (for instance, the VERY first memory mapper
circuits I built myself once, as an experiment, were put together
better already than the circuits used inside these machines).
In fact, these machines are built so lousy in just about every way
(never did like the 8235 anyway), that if you have one, there's no
shame in piling these up in some corner, to maybe use them for spare
parts some time.
I know, a REALLY sad, sad way to go for any computer.... ;-((
But hey, if you could use a part from such an old 8235 to bring
another MSX back to life, that might be a good deal indeed...
The newer 8235 models have a completely different designed
motherboard: much more compact, all ROM's packed together in one,
etc. In fact, these 8235's look (on the inside) just like the Philips
NMS 8245 (that one with DS drive, and non-adjustable keyboard). The
print-layout IS different, but most (maybe even all?) parts are
numbered/named the same as in the 8245. In fact, when you have such a
newer model 8235 in front of you, you can just take the service
manual for the NMS 8245, and use this as if it were of this 8235,
just about everything checks out (you might have to look somewhere
else on the circuit board for a certain part though)! Only power
supply circuits, and mechanical construction differs between these
newer 8235's, and the 8245 (and the SS vs. DS drive, ofcourse).
I guess that would explain the disappearing of such a dumb memory bug
too, simply a more modern circuit & printed circuit board layout in
the 8235/20.
BTW: I think this memory bug on older 8235's has some easy 'fix', I
could try and look it up, if anyone wants it.
I'm not sure what this memory bug was about, I did reproduce it
myself once or twice, it more or less simply came down to:
'unreliable memory mapper switching'.
Greetings,
Alwin Henseler ([EMAIL PROTECTED])
http://huizen.dds.nl/~alwinh/msx (MSX Tech Doc page)
http://www.twente.nl/~cce/index.htm (computerclub Enschede)
Aaahhh, for once, the weather really was great, today in Zandvoort!
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