
The MOnSter 6502: transistor-scale replica of classic MOS 6502 microprocessor - ingve
https://monster6502.com/
======
jacquesm
I can't get enough of that project, it's brilliant in picking the one target
that is still feasible and yet so complex that it illustrates the magic that
makes an integrated circuit useful: the _only_ reason you are using a CPU is
because it is integrated. A non-integrated CPU would be prohibitively
expensive and terribly slow, even with today's surface mounted devices.

~~~
leoc
Modern CPUs, sure. Apparently the original microprocessors were actually
faster when implemented with discrete components though:
[https://en.wikipedia.org/wiki/Datapoint_2200](https://en.wikipedia.org/wiki/Datapoint_2200)

~~~
hathawsh
Wow, as that Wikipedia article explains, the 8008 was effectively developed
through a prototyping process involving 100 TTL chips. Also, it sounds like
CTC (Computer Terminal Corporation) invented the circuit and later gave Intel
full rights to turn it into a chip and improve upon it. Intel was simply a
contractor who knew when to do some work for free in exchange for IP rights.
Did Intel have any idea how successful their strategy would turn out? Amazing!

~~~
zerohp
Prototyping using TTL chips to validate the logic design was still common
throughout the 1970s. 100 TTL chips is pretty small.

The Motorola 68000 team published several papers that are still available
through IEEE that describe the design process. They built a prototype from TTL
chips which allowed them to rapidly iterate the microcode, nanocode, and
programmed logic arrays without having to wait for samples to come back from
manufacturing.

~~~
jacquesm
That must have been several boards at least, even at TTL scale integration and
using components like adders and decoders as the building blocks.

~~~
jandrese
There is a FAQ on the page that explains that a 68k built in the same way
would require a board 1.7m square.

~~~
jacquesm
Which is not practical for board size, so it most likely would have been some
kind of backplane with plug-in boards for the various main sections of the
CPU.

------
bprater
From their FAQs:

>> How big would a modern CPU be at this scale?

>> The Apple A8X, found in the iPad Air 2, contains about 3 billion
transistors. (This is comparable to the number of transistors in modern
desktop computer CPUs as well.) At the scale of the MOnSter 6502, that would
take about 885,000 square feet (over 20 acres or 8 hectares) — an area about
940 ft (286 m) square.

~~~
Sohcahtoa82
At that scale, I imagine the speed of electricity is a significant issue
limiting clock speed.

It would take light about 956 nanoseconds to travel the 940 feet across that
theoretical CPU. Assuming that was the limiting factor in your clock speed,
that would cap it at 1.05 Mhz.

Obviously, it's going to be far more complex than that, but I'd be really
surprised if they could get the clock any faster than that.

~~~
loser777
You would be murdered by the capacitance of the discrete components before
even seeing MHz on the horizon. (The author cites gate capacitance here as
limiting _this_ "small" CPU to 60 KHz)

~~~
IWeldMelons
You can use BJT's. They have quite low capacitances.3pf for a typical
transistor.

------
aavotins
I wish projects like this caught on and became an art trend, as in digital
artists would create pieces like this and put them for sale. I love the idea
of smart "paintings" that illustrate the technical detail and inner workings
of a CPU, running a simple program, source code of which is printed out and
put inside the frame. Perfect addition to a geek nest, as I detest the name
"man cave".

edit: elaborated on art trend

------
jefffoster
Love projects like this!

If you're ever in Cambridge (UK), pop along to the Computing History Museum
and see "Mega Processor"
([http://www.megaprocessor.com/](http://www.megaprocessor.com/)).

------
lisper
Previously on HN:

[https://news.ycombinator.com/item?id=11703596](https://news.ycombinator.com/item?id=11703596)

~~~
dang
Also
[https://news.ycombinator.com/item?id=14386413](https://news.ycombinator.com/item?id=14386413).

------
kazinator
> _The MOnSter 6502 is relatively slow compared to the original, thanks to the
> much larger capacitance of the design._

Though that is all true and good, decent speeds are possible with discrete
designs. A decade before the 6502, discrete component mainframes hit clock
speed like 35 Mhz.

Those used BJT's; that's the main difference. Low impedance inputs exhibiting
low parasitic capacitance.

------
jmull
So beautiful.

I wonder if it could be done in a similar way but run full speed? From the
FAQ:

> Does it run at the full speed of an original 6502 chip? > > No. The MOnSter
> 6502 is relatively slow compared to the original, thanks to the much larger
> capacitance of the design. The maximum reliable clock rate is around 60 kHz.
> The primary limit to the clock speed is the gate capacitance of the MOSFETs
> that we are using, which is much larger than the capacitance of the MOSFETs
> on an original 6502 die.

I think I'm imagining most of an entire motherboard of something similar to
the C64 or Apple ][ implemented this way, wall mounted along with a display
and controls, with a classic software library.

~~~
ChuckMcM
This is one of the key things that integrated circuits bought you, when moving
from discrete to integrated circuits you could switch the transistors faster
because they needed either less current (TTL) or less charge (NMOS/CMOS) to
switch. Or conversely, the same charge could switch them faster.

So if you look at the highest performance discrete computers of their time,
things like the CRAY the CDC machines, etc. You'll see that they consumed
larger and larger currents to achieve the switching rates they needed to
achieve and increasingly exotic cooling systems (with the Cray's flourinert
systems being pretty damn awesome).

I find it fascinating to walk from the ENIAC to the 704 to the B5500s, and
PDP-8's and 11's, to microprocessors to systems on chips. Each step in
integration let you make things smaller and run them faster. It wasn't until
Moore's law broke down in 2004[1] and the world became multi-core that this
really stopped happening.

[1]
[https://ieeexplore.ieee.org/document/1430623/](https://ieeexplore.ieee.org/document/1430623/)

~~~
pkaye
Yes the earlier Cray computers used ECL logic where the transistors were never
in saturation so fast switching time but more current dissipated.

------
lbriner
So a "modern" CPU to the same scale would be around 20 acres. Hmm, I'll start
saving up now.

~~~
ygra
And probably not faster either, considering that the thing runs at 60 kHz due
to its size.

~~~
TylerE
A 20 acre square is about 925ft to a side.

Speed of light is really starting to matter. That's about a nanosecond just
for signal to propogate, and that's assuming a straight wire with no
intermediate components.

~~~
caymanjim
The speed of light often seems so fast as to be infinite, or at least hard to
comprehend, in daily life. I was surprised the first time I calculated the
minimum possible round trip time from New York to San Francisco, as the crow
flies: it's just under 28ms not counting any overhead whatsoever from
switching, electronics, etc. It amazes me that an actual network ping is only
about double that, considering all the overhead of switching, and that light
doesn't travel at full speed in fiber optic cables.

~~~
abricot
No kidding, high speed traders are spending big bucks on getting an advantage
over fiber networks by using microwave links spanning continents[1]

[1]: [https://arstechnica.com/information-
technology/2016/11/priva...](https://arstechnica.com/information-
technology/2016/11/private-microwave-networks-financial-hft/)

~~~
caymanjim
I worked on an algorithmic trade platform for an options broker/market maker.
We bought rack space next to the ISE exchange's racks, which comes at a
premium over rack space ACROSS THE ROOM.

------
colanderman
> 630 located on 164 quad transistor array chips

Eh. That's kinda cheating.

(I'm joking of course… this is impressive. Apparently they had to use the
chips because discrete 4-terminal NMOS transistors are no longer
manufactured!)

------
bogomipz
The post has a question:

>"Is it truly a "discrete 6502?"

I read the answer but didn't understand the answer given. Can someone
elaborate on this? Wasn't the original 6502 an "integrated" chip? When I think
about a "discrete" CPU I think of something like an older main frame where the
different functional units of the CPU might be spread over a few different
circuit boards with busses connecting those boards. Is my understanding of a
"discrete" CPU incorrect?

~~~
pwg
The context here revolves around the definition of the word "discrete" and the
fact that they are using "discrete" in terms of "transistors" as in "discrete
transistors".

When used in that manner, "discrete transistors" generally means that each
individual transistor is on/in one single package. The item pictured here:
[https://www.sparkfun.com/products/retired/12852](https://www.sparkfun.com/products/retired/12852)
is a "discrete transistor" (the plastic package contains one single
transistor, the three leads connect directly to the collector, emitter, and
base).

Now, in the case of this design, they explain that they are unable to purchase
actual discrete transistor packages because no one makes the appropriate
MOSFET transistors as single transistor to a package items anymore. So they
had to use four transistor packages instead of single transistor packages. So
under a _strict_ definition of "discrete" they did not use "discrete
transistors". They then provide their rationale for why one could view this as
still discrete in a less strict usage. It is then up to you to decide if you
accept their rationale.

~~~
bogomipz
I indeed missed the context here. Thank you for the clarification and
excellent explanation. Sparkfun looks like a great resource. Cheers

------
throwaway456321
beautiful, looks like a work of art !

~~~
jacquesm
I think that by most definitions it is a work of art. It is not practically
useful, it is beautiful to look at (at least, to me it is), it is unique (for
now) and it took a labor of love to be brought into this world.

~~~
aswanson
I think it would be useful to visualize how an assembly instruction works, to
teach how it is executed in hardware.

~~~
jacquesm
I think the various 'soft' versions of the 6502 would serve that purpose
better, but yes, you could use it as a teaching aid.

------
jedimastert
What's the device he's plugging the chip into, with the vga and ps/2 output
ports?

~~~
CamperBob2
Looks like a modern replica of a KIM-1 or another early single-board trainer.
Something like that would be useful for testing, since the replica CPU won't
work if you just drop it into an Apple II or other 8-bit consumer PC.

------
jhallenworld
I'm surprised the clock generator scaled. Is the clock circuit the same as on
the 6502?

------
gnulinux
I love and miss this sort of actual hacker news. I wish we had more of these
here in HN.

------
utopcell
Crucial questions about the project remain unanswered:

Does it suffer from Spectre attacks ?

~~~
InclinedPlane
Definitively not. The MOS 6502 lacks speculative execution functionality, it
also lacks any sort of instruction or data cache whatsoever.

------
twic
I remember reading about someone making a working version of some very small
ARM core in conductive ink on a T-shirt. However, i can't find any description
of this on the web. Did i dream this?

~~~
jecel
You might be thinking of the ARM printed on plastic as thin film electronics:
[http://armdevices.net/2017/05/21/0-01-flexible-plastic-
arm-p...](http://armdevices.net/2017/05/21/0-01-flexible-plastic-arm-
processor-by-pragmatic/)

~~~
twic
It wasn't that, but that is brilliant!

------
rbanffy
I wonder how much would it cost to make them in a factory. How long does it
take a robot to place 5K components on a board and send it through the oven?

~~~
bacon_waffle
Cost of placing a component like the FETs here, would be roughly $0.04, plus
say $0.01 for the part. The PCB would be something like $50, maybe a bit more
to get the nice looking ENIG finish. There would be a bit of extra money
required for the power supply, connectors, handling, solder stencil, etc.

seeedstudio.com does online quotes, but you'll need design files.

~~~
rbanffy
So, it should be about US$250 for the discrete components, plus $50 for the
board.

I'd totally pay $300~400 for one.

------
matheusmoreira
What a beautiful board. I love how you can see the processor working. I'm sad
that they have no plans to make other processors as well.

~~~
userbinator
It may inspire others, however; and even if it's not a different processor
(I'd love to see a Z80 version) there's still plenty of room to shrink this
one and yet remain discrete --- looking at
[https://cdn.evilmadscientist.com/sites/6502/images/A1_4.jpg](https://cdn.evilmadscientist.com/sites/6502/images/A1_4.jpg)
you can see there are huge areas of empty space between the transistors and
LEDs, and that package is not as small as SMD transistors come. Halving each
dimension (1/4 the area) should be possible in a revised design, reducing PCB
costs and making it more palm-sized. Alternatively, the same size of board can
hold 4x the transistors, meaning a Z80 would fit comfortably.

~~~
matheusmoreira
Is there a way to set the processor's clock? It'd be nice if the user could
slow it down make it easier to observe and understand the state changes. Maybe
even support breaking execution in order to read the state.

A Z80 or 68k would be way cool!

~~~
ChickeNES
You can do that with [http://visual6502.org/](http://visual6502.org/) today!
:)

------
QuadrupleA
Very cool! It's actually simpler / smaller than I expected. Even back then I
imagined CPUs having a lot more transistors.

------
VectorLock
I'd love to have a giant wall hanging reproduction of a Tamagotchi running on
this. Would definitely pay good money for it.

------
ngvrnd
It's said that no work of art is finished, only abandoned in frustration. Is
this work of art ongoing, I wonder?

------
dep_b
Very nice for educational purposes I imagine. Or just hang it on your wall
running your favorite code!

------
gesman
+100!

It will inspire kids / young people to learn and create things beyond what's
possible today.

------
jhallenworld
Selling them will be interesting.. it will need something like a KIM-1 front
panel.

------
apple4ever
That is just so COOL.

I love the LEDs illustrating what is going on internally.

------
elfchief
Now if only they'd sell me one. :/

~~~
lowlevel
Yeah... so much want... sigh.

------
postalrat
Cool. Let me know when it is available (if ever).

~~~
apetresc
The article links to a mailing list specifically for that.

~~~
postalrat
I know. I've been on it for quite some time.

~~~
AlexCoventry
What's cool about it? It's totally bizarre to me that someone would spend two
years on a project like this.

------
leowoo91
2019: big visible CPUs trend maybe?

