Re: 264 kernals, bugs, ntsc hack, etc.

From: Gerrit Heitsch <>
Date: Wed, 31 Aug 2011 20:08:03 +0200
Message-ID: <>
On 08/31/2011 07:36 PM, Hársfalvi Levente wrote:
> Hi!,
> I did meet the infamous "28 ff" bug, though (which is IMHO present in
> all revisions).

Oh? Never heard of that one. Can you describe it?

>> 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.

So far I only once had problems with an EPROM, this one found in an 
Oceanic OC-168 drive (1541-II clone), after about 20 years it started 
losing data. Easily fixed thanks to ebay, picked up a real 1541-II ROM 
(wiht MOS logo).

> 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).

I also prefer the real hardware if I can get my hands on it. Ok, that 
means the system itself. Current power supplies are better than the old 
ones and the SD2IEC instead of a real floppy drive is also nice now and 
then. Still have my share of 1541(-II)s in working order though.

>> I also put heatsinks on CPU, TED and PLA to hopefully extend their lives.
> I haven't found heatsinks, yet, that would fit perfectly.

To give you can idea, go to and search for 'V 5619' 
(Search field, upper left corner). I used the one for 28pin on the CPU 
and the one for 40 pin on TED. A _small_ drop of heatsink compound in 
the middle, place on chip, move a bit to spread the compound around. 
Then just a drop of generic adhesive (not epoxy) on each end of the 
heatsink so it connects the exposed part of the chip with the end of the 
heatsink. Let dry for a few days. Done.

This way the heatsink can be removed without damage if necessary. So far 
not one has fallen off by itself.

(Remember to mark pin 1 if you use a 40pin heatsink on a 40pin chip)

> ...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).

Another indication that the first attempts of MOS at HMOS-II were not 
quite up to par... Of course that doesn't mean that all CPUs and TEDs 
from 1984 will fail early, probably most of them that will have already.

Somewhere in my archive should be a 7501R1 which worked the last time I 
tried it.

> I don't remember
> TEDs and PLAs dying "on me" so far (...well, unless stressed, ie. the
> TED) anyway.

There is a replacement for the PLA available now, which means that the 
ones you have won't fail.


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Received on 2011-08-31 19:00:18

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