Re: 264 kernals, bugs, ntsc hack, etc. (was: 264/TED/Plus4 Story)

Hi!,


On 2011-08-30 18:41, Gerrit Heitsch wrote:

>> The other (so far only found in eprom) version is originally 318004-05,
>> and it also contains further modifications to the character set. The one
>> that I have here is in a NEC 27C128, whose datecode appears to be 8614
>> (see photos) ie. it had to be programmed after the spring of 1986.
> 
> I try to remember the difference between the -04 and -05. It was an easy
> to reproduce bug and back then I was pretty annoyed when I found out
> that my first C16 had the -04.
> 
> It's not the well known math crash that can be triggered with
> 
>  ?5+"A"+-5
> 
> this one still works with -05.

Ah, I never programmed in Basic much, so that I could stumble upon these
bugs in practice.

I did meet the infamous "28 ff" bug, though (which is IMHO present in
all revisions).

>> As to how and why these (new) differences in the character set?
>> Honestly, I don't know (...I have no idea about especially the few
>> graphical characters that have been modified). Also, someone's yet to
>> find a Plus/4 with the first and a C16 with the second version; I could
>> never encounter either of those combinations yet.
> 
> Maybe the Plus/4 was imported later when all the C16 were already sold
> and they decided to finally fix the bug from -04? On the other hand, the
> first -05 PAL kernals are from the end of 1984.

Yes, that sounds reasonable. Still not sure why they also had to modify
some more characters though.

>> Well, I think I know the technical details of the PAL-N machine fairly
>> well (see http://coroners.no-ip.hu/dc16 and
>> http://coroners.no-ip.hu/c2rgb for details). Unfortunately, speaking of
>> its story, that'd not be the case (...beyond things that one can read
>> around the net), which is a pity.
> 
> I'd be interested in that story as well. I mean making new TEDs just to
> export the 264 systems to south america? Ok, they only modified the
> existing TED slightly, but it's still a whole new production run
> including testing.

Yes, yes, yes. Definitely.

> Back then I got a cheap EPROMmer that had 2 sockets and could do certain
> things on its own (like copy). Which made it very easy to migrate the
> ROMs to CMOS EPROMs. Otherwise it's very slow. It still works though.

That's a stage I, well, seem to have missed. I did have a primitive
eprom burner, but only ever had problems with Eproms in general.

> Interesting... But why make a C16 switchable between PAL and NTSC? Is
> there something only an NTSC system can do? Or is it the 60Hz you wanted?

I haven't had an NTSC machine, well, until some years ago (when I bought
one for reference). Even before that, I modified a C16 so that it'd work
in NTSC permanently (...one of the few times I ever used Eproms), it was
just slightly incomfortable to use. I was very interested how the NTSC
mode in this model really works in practice (...not especially the
implementation itself, but practical questions; say, how much the colors
of PAL and NTSC palette match each other, how does the color resolution
of the two modes look like (PAL is theoretically better in the
horizontal direction, but in the vertical direction, NTSC should win),
and similar questions that I couldn't answer, until I could see them all
myself). Also, today, the scene is much more "global" than it was back
in the times. Back then, nobody ever created titles that had to be
PAL-fixed, let alone NTSC-fixed, because technically advanced titles for
NTSC-land (together with an American Plus/4 scene, and together with the
need for such titles), as I perceived, were virtually non-existent (much
unlike the contemporary American C64 software industry and scene).
Today, programs are shared via the Web, and whilst the number of 264
enthusiasts should be relatively small, they're from all over the World,
including the US and Canada. Today, I'd say, there's some challenge to
keep NTSC compatibility, as much as it's possible, when/while
programming new stuff. ...Generally, I prefer the real machine over
emulators; and it also looked fun to make a hack that provides both PAL
and NTSC option on the same machine (so that both my and other people's
stuff, if there's some, can be tested on the real iron, without much fuss).

> You have the 74LS257 socketed but the RAMs are soldered?

Heh... this mainboard has actually seen a lot. The set of rams are
actually the fourth set in this place. The muxes were probably replaced
at another occassion when the thing failed. ...Neither of those fixes
were actually performed by me - they all go back to the "old times", ie.
1992 and before.

> I also put heatsinks on CPU, TED and PLA to hopefully extend their lives.

I haven't found heatsinks, yet, that would fit perfectly. ...Anyway, the
CPU, as you can see, is from the previously mentioned (I believe:
stable) 1990 series (...wasn't my fix either: got that one when the
thing failed for the last time, still back in 1992). I don't remember
TEDs and PLAs dying "on me" so far (...well, unless stressed, ie. the
TED) anyway.


Levente

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