From Germany:

https://www.forum64.de/index.php?thread ... pu-ersatz/

Interesting, and a thorough ground-up effort by the look of it, decapping chips, photographing, drawing polygons, simulating, and using the original schematics from Donald Hanson. The present state seems to be a (presently oversized) carrier board with an FPGA on it, and a phase accurate model of the 6502.

There is a hope, I think, that once the project is finished, the sources will be made available.

From the nearby thread MOS 6509 look-alikes?:



(Where we see that Jim Brain's 6509 solution is working, is small, and is open-source - hurrah! It won't suit the forum64 purpose precisely, because all the undocumented behaviour of Commodore's various chips are important over there. Also, that's just the 6509 whereas this is capable, or intended to be capable, of being 8 various 6502ish chips.)

You know, it's just now striking me that that's essentially the exact same scheme for extended memory addressing as the PDP-8 used.

That's an interesting observation commodorejohn. I am not very familiar with the 6509 and its memory management extensions, but it does not surprise me that it resembles the mechanism used on a low-cost minicomputer: the PDP8.

Since I've been involved on this and other vintage computer forums, it has become obvious to me that many of the innovations seen in microprocessors are derived from developments in mainframes and minicomputers of the 60s and 70s. There are certainly innovations in modern processors that stand on their own. However, it is certainly very thought provoking to study vintage processors and find their solutions, in some form, being applied in modern processors.

Our "technological grandfathers" may not be so backward and stupid after all.

_________________
Michael A.

I’m not a bit surprised. If you look back at obsolete technology, our clever "technological grandfathers" tried to do as much as possible with what was then (compared to now) very limited resources. Every transistor cost a relatively large amount of money, so designers, if they could, where possible, would get maximum use out of each one.

In my workplace, we have various electronic systems dating from the late 1960’s through to current “tried and tested” technology (we don’t do state of the art, as these are critical systems where reliability is very important).

The 1960’s designers where possible use transistors for two functions!

So I am sure that a lot of the principles and design ideas that engineers came up with in the past would have been very well thought out.

So it’s not surprising that some of these ideas have been taken up by designers of later technology. Where the costs are much lower.

Mark

Our ancestors sure had some nice ideas, but sometimes the technology which had been available back then wasn't up to it.

Back in 1958, computer pioneer Konrad Zuse had filed patent DE1190413, ‘Lighting device photoelectrically-controlled by backlight’.

He envisaged multiple light sources which are deactivated by photoelectric cells if these cells detect other cars in their vicinity.
But with the technology of the 50s, it wasn't possible to manufacture something like that working in a reliable way.

The patent went buried in the German Patent Office’s archives...
...until the adaptive multibeam LED headlights were introduced by the car industry.

;---

Hmm... scary thing is, that when looking down at the top of his mechanical Z1 computer (1938) from high above, it somehow resembles a chip layout.

Looks like old Zuse had "liked" 80x86 PCs about as much as we do nowaday:

The board is much smaller now! Just a bit more than a regular DIL40 package:

- -

Looking good!

Yes... and this should also give a replacement for GoDIL40... keeping fingers crossed
that there won't be too many quirks in the prototype(s)!

That would be very welcome - I take it those are active level shifters? (So the mapping of the 40 pins to ins and outs will be specific to 6502, but the electrical compatibility and speed will be better than passive shifters??)

These are passive level shifters - like it is on the GoDIL board. Power supply can be configured via solder bridges.

The 1st prototypes had active level-shifters...

it was quite tedious to sort out which pins were inputs, outputs or possibly both depending on the CPU type:



Therefore I decided to go the KISS route too! (Passive level-shifters, weak pull-ups in order to not
interfere with tricky bus designs too much. Due to the solder pads on the upper side of the PCB
these pull-ups can be modified with another resistor in parallel).

The JTAG Connector (Cable made by Tag-connect) is a bit different/more complicated than usual:

The connector allows (apart from flashing of course) to supply power to the board
without configuring the power pins and it also has a few additional
I/O pins (meant for an UART with hardware handshake).

That means: There will be a special adapter board to connect USB-Blaster, 5Volt and
possibly with RS232-USB interfacing (FTDI or CP2102) included.

Ah right - which gives the advantage of fitting into a Z80 or 6809 socket instead, with a suitable design loaded on the FPGA.

Yes... and due to the smaller PCB size this should be no problem in most cases.
In order to keep the visual experience more appealing (i.e. more similar to the chip to be replaced)
the final boards will be produced in matte black color. But that's certainly only important to me!?

I didn't want to wait until weekend... and made some first tests
via boundary scan with one of the pre-series-prototypes:



I'm glad that everything's fine so far! That means: I can now port
the code from the first prototype to the new ones.


Here you can see the board in one of the targets: