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640K Ought to be Enough for Anyone 
Monday, January 12, 2015, 11:00 PM
Posted by Administrator
For most DOS software, this might be true.
I am referring to that "quote", because a few days ago, I upgraded my Schneider (Amstrad) PC 1512 to 640KB RAM. And yes, for this machine, it is enough to run most of the programs of an exciting decade.

But where does this "out to be enough" sentence come from ?

Most of the "googled" internet hits says Bill Gates said this.
At least there is one source of a similar sentence he said:
In Infoworld magazine from April 29th, 1985 (Vol.7 Issue 17), you can read at page 5:

When we set the upper limit of PC-DOS at 640K, we thought nobody would ever need that much memory.

William Gates, Chairman of Microsoft

You can read the whole article here (click on picture):

But some already further investigated some more possible sources, so it's difficult to say "Bill Gates" said this. Go on reading at

At least, this all is (interesting) history.

P.S.: I have seen a negative feedback (below 3) for this entry. Please give me a note why with "add comment", thank you in advance.
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Pioneer hardware with a (meanwhile) rare CPU: Cosmac Elf (1976) ... and his successors 
Sunday, January 4, 2015, 11:00 PM
Posted by Administrator
This is really cool:
The "ancient" CMOS CPU from RCA, the 1802, can be still found in SBC projects like the "1802 Cosmicos" and the "COSMAC Elf 2000" !

Why is a SBC so interesting with the RCA 1802 ?
Because the CPU is also used in many satellites and (former) rockets (it was also manufactured as a radiation resistant variation), and it was one of the first 8 Bit CPUs available, too.
Some of the first video consoles used the RCA 1802, too.
In 1976, it was the fastest (3.58Mhz) running CPU, unfortunately no bigger computer manufacturing company used it for their models.
The CPU was also used in a rare homecomputer named "COMX35", but that's the only one of his kind I know.
The first SBC, the Cosmac Elf, was published in August 1976 in "Popular Electronics".

You can take a look at the articles also >here< and >here<.
You should also visit


Hans Otten has his own page about his 1802 Cosmicos SBC:
Infos about the "COSMAC Elf 2000" can be found here:

But you don't need real hardware to try to program a RCA 1802.
There is a really good emulator:
Another emulator can be found here:

Take a look at for a first impression about the CPU.
Then look at the instruction list at

Picture was taken from wikipedia.
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Merry Christmas to all blog readers 
Wednesday, December 24, 2014, 03:00 PM
Posted by Administrator
I wish you a merry christmas and a happy new year !
Thank you for reading my humble vintage computer blogs, some already for years.

The shown animated GIF is taken from the "Sierra Electronic Christmas Card 1986" and runs with MS-DOS 3.2 and above, also on my old Amstrad (Schneider) PC 1512.

You can download the AGI or SCI version here:

There are much more animations (be amazed, even Santa will show up), not only a fireside.

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RAM Upgrade Amstrad (Schneider) PC1512 from 512KB to 640KB 
Monday, December 22, 2014, 12:30 AM
Posted by Administrator
Almost all Amstrad/Schneider PC1512 web pages disappeared meanwhile.
I tell you that, because I looked for hints about upgrading my PC1512 from 512KB to 640KB RAM. After all, that wasn't too difficult, although it's NOT enough just to insert 16 pieces of 4164-120 Dynamic RAM chips (64KBx1 per chip). You have to set a jumper too, unfortunately this wasn't documented in the manual nor on a web page I found.
There are really A LOT OF SCREWS to be removed, until you can take a look at the mainboard:

The smaller red rectangle shows the jumper position. The jumper was hidden by the metal plate/radio shield which covers the mainboard. You have to remove the shield also to see the jumper :-(
This costs at least 2 hours of disassembling and reassembling, but success is sweet:

Wikipedia is wrong with the description of the RAM upgrade.
There is written "it could be upgraded to 640K of RAM with an expansion pack commonly known as a 'top hat'". there is no such "expansion pack". You need only 16 DRAM chips each with 64KBit memory. Nothing else.

P.P.S.: There is a tech manual online, and if you know the words you have to look for, you will find also the hint for the above mentioned jumper, see "related Link".
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Repairing a Macintosh IIci power supply - NIGHTMARE !!! 
Sunday, November 16, 2014, 07:05 PM
Posted by Administrator
A few days ago I got a working Macintosh IIci, which I want to use for Apple's UNIX (A/UX) experiments. After turning it on, it ran for about 5 minutes, then a creepy sizzle sound occurs and it began to stink like hell.
I immediately switched the Mac off and tried to look what happened.
I located the strongest smell from the power supply, so I tried to remove the power supply cube.
First annoying problem: I didn't know how to remove it, there were no screws.
After I used Google, I found this picture:

There is a kind of a pillar with a tab you have to pull (away from the power suppy), then it will be possible to pull it out.
But this was not the only problem. Getting both sandwich-alike arranged pcbs out of the cage is really hard. There are three screws inside the case, but there is a molex-alike plug also which was tightened like hell. And you have to remove the fan and a small metal box with the AC plug also btw.

The power supply PCB finally showed the bad guy ...

... it was a blown capacitor (0.047 uF):

After replacing it, the NIGHTMARE began.
I tried 2 hours to reassemble it, but the screws didn't hold it again, and the small AC plug metal box didn't fit in the bracket/clips, also because you have to use also one of the screws which hold the lower PCB:

Also, connecting the fan power has to be done in the right order, BEFORE reassembling the AC plug !

I was really pissed off, the designer (ASTEC) of the power supply must be a real idiot.
It is really NOT designed to be fixed.

Last but not least, the Macintosh IIci worked again, see the screen:

The related link points to Al Brower's Mac IIci pages.
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