|  C16 Prototype | This C16 prototype board has been sold on eBay in date 2017 May the 14th (€1110,00). The seller has specified in the description that the CPU 8501 socketed in it, is a replacement for a 7501 gold. It's still hard to suppose if the original CPU was broken and then removed by him, or if he simply knew about that.
Bil Herd has confirmed in this thread the authenticity of the prototype:
The C16 prototype you saw is real, Okobo-san (manager of Tokyo office engineers) sent me a telex warning it was coming (His words were Gomen nasai B-san), they briefly examined the cost savings of making a single sided board with limited solder-mask, etc., vs the cost of dual sided and smaller. MY gut is that the jumper insertion (0 Ohm resistors) was too problematic, or the square area of the PCB, even single sided, didn't justify the offset in other costs. I had to grin like a madman when I first saw this unit (The one on eBay probably has my fingerprints on it including my now missing finger) as this kind of cost savings out-of-the-silly-box thinking was the heart of CBM's mass production mentality. Apple was selling for $1,799 and we were trying single sided PCB's and custom ICs... Woot!.
(...)
My memory is that the 116 and 264 were done but the C116 was being ignored and the 264 had become the Plus-4. Tokyo stepped in and made the C16 which is really the C116 design. Their first swing at the C16 was the single sided, and then production dual sided that you see.
I suspect that this was Sam Tramiel instructing the Tokyo office to produce this initially as a cost reduction though I think that he and Okubo were gone before production, but it's tough recalling timelines so many years later. The C16 was literally a purchasing and specification task as the C116 and chips were done, and Tokyo as really good t managing vendors and custom assemblies like we got from Mitsumi who made the keyboard, modulator and several connectors.
I think we in the US office were surprised that the C16 actually did have some legs, and the housing was pennies vs the C116 which would have had to shoot a few million before the plastic was as cheap.
JamesC has followed up with further investigation:
I did a little Googling, and found the FCC approval date for the C16:
https://fccid.io/BR98YV-16 (scroll down to Grants, then click the EAS tab)
The C16's FCC registration was requested on 22 June 1984, and granted on 26 July 1984. This tells me that the production (dual-sided) motherboard was completed, CBM tested, and outside RF verification acquired by mid-June 1984. Since the prototype chips are all dated late February into March 1984, and the ROMs have stickers indicating March burn dates, I feel it safe to say that the prototype board was made about the same time (early March 1984).
It's also interesting to note that the prototype board has mini-DIN connectors for the Datasette and joysticks, just like the Plus/4 (and FCC-approved 264).
After being sold, the C16 prototype has resurfaced in this thread on Forum64.de written by the user Pentagon, whose friend has bought the prototype and asked to keep secret his name due to privacy demanding.
The prototype has come with a case, although it has never been taken in a photo while the auction was running, and this case is clearly a C64 one, repainted and visibly hand-woven, where all the vents and the breaches to adapt it to the sockets have been cut by hand too. From the inside, what remains of the C64 cartridge port can be spotted. Even the keys on the keyboard have clearly been made by hand, where the keys have been carved in the plastics and some of them only have been painted by hand.
Examining the back of the board with a magnifying glass, the handmade soldering of the whole board can be easily noted, with tons of bridges anywhere, making it surely unsuitable as a marketable serial product.
The buyer has placed back a 7501 (quite rare too in these days) instead of the 8501 the seller used to replace the original CPU which was faulty due to a broken pin.
The C16 prototype has been turned on to be tested with Finders Keepers for a short time, 'cause it actually has worked flawlessly, but showing high temperatures after a while. What really appeared to be absolutely different is the TED sound, described as "heavier and very good". Once dumped and analyzed, the two ICs relative to TED seems to be absolutely the same as the C318006-01 Basic ROM and the C318004-04 Kernal ROM. Somebody has pointed out that the difference in the quality of sound is a straight consequence of the particular electronics onthe board, and also due to the implementation of a TED 7360R7, father of the well known MOS 7360/8360 officially marketed in the final product.
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