Re: 264/TED/Plus4 Story

Hi!,


On 2011-08-29 17:11, Gerrit Heitsch wrote:
>> Yes. From the machine:
>>
>> 318030-01
> 
> Thank you. I try to assemble a list of all chips with a MOS/CSG logo
> made for the VC20 and up.
> 
> ...
> If this is the (compared to other MOS ICs) rather flat case with the
> angled sides and grey lettering, then, as far as I know,  it was made,
> or at least packaged by GI (General Instrument) in Taiwan.

To keep the story short: I took a Plus/4, a modified rom card and two
Hungarian Kernal roms (the 318030-01 and an Eprom) today, and made dumps
of the chips at last. The ultimate result is that there were in fact two
different Hungarian 264 Kernals around. The mask rom and the other
version - taken from a 1986 Plus/4 -, much unlike I suspected, don't
carry the same content.

I've passed the dumps on to Bo Zimmerman, and he already acknowledged
them so I'm sure they'll appear on zimmers.net's file area pretty soon;
yet I also copied all the stuff to a "site" (a Linux box beside the
desk, that is...) so that if people want, they can have a look at the
files. The link is http://coroners.no-ip.hu/stuff/p4kernal . (The
machine isn't up all the time, but it'd always get back online in some
hours at the worst case).

318030-01 is based on 318004-04, replacing some graphical characters only.

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've made a quick-and-dirty diff routine in plus4emu so that differences
could be spotted. diff.png shows the original charset, 318030-01, and
the later eprom version (in that order from top to bottom). Red: char of
original set and dump 1 don't match. Cyan: char of original set and dump
2 don't match. Yellow: char of dump 1 and dump 2 don't match (...a
special case appears: dump 2 only modifies characters that were not
modified in dump 1).

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.

> Yes, the Kernal ROM (and the TED for other PAL variants in south america
> (*)) is the only location specific IC in the 264 series. They also made
> the 318004-04 until late 1984 and only then switched to the bug fixed
> 318004-05. You can sometimes find a C16 with all ICs from 1984 except
> the 318004-05 with a 1986 datecode.
> 
> (*) There is a picture of a 8365 up on plus4world.com. There is also
> supposed to be a 8366, but I haven't seen it yet.
> 
> In my C16s I have replaced the ROMs with properly programmed 27C128.
> Saves about 100mA in power, together with using a better power supply
> that keeps the system a few watts cooler without any irreversible
> changes. The original ROMs have been kept of course.

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.

Neither I have ever seen a PAL-M (Brazilian) TED.

It's interesting how things "converge" to similar solutions, given
similar-ish initial conditions. I've never really used Eproms but
created a small flash board with a cmos priority encoder + a 128k flash
chip sometime ago. It never made it past the prototype stage and it
still looks very hacky, but well, it too, reduces current consumption of
the machine by a reasonable percent. (...You can also find a photo of
that hack - it's in fact a flash + PAL/NTSC switch hack together - at
http://coroners.no-ip.hu/stuff/ ).


Levente

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