Hi,
I first apologize not being able to write a quite long post in German.

I will soon add a Delta-1 to my collection ("ordered" it as a birthday gift) and wanted to dig into the authorship mystery.

As it is now easy to browse ROM data files dumped for emulation purpose, I compared the Delta ROM with some candidates, all F8-3850 or F8-3870 based:
- Novag CC MK I, 1978, 2Kb ROM, 256b RAM (D. Goodrich)
- Boris, 1978, 2.5Kb ROM, 256b RAM (D. Lindsay)
- Boris Diplomat, 1979, 2.5Kb ROM, 256b RAM (D. Lindsay)
- Novag Pocket Chess/Chess Traveller, 1980, 2Kb ROM, 64b RAM (M. Johnson)
- Novag Delta-1, 1980, 4Kb ROM, 312b RAM (to be identified)

Of course I could not perform such a comparison with 6502 based devices, such as CC MK II or MK III. Anyway Mike Johnson is present with the Pocket Chess; and Peter Jennings indeed lacking.

But let's step forward with the ones that can be compared on a byte to byte basis:
- I could find no similarities between Delta-1 code and CC MK I nor Pocket Chess
- on the other hand, I found significant identical blocks of bytes between Delta-1 and whichever Boris/Boris Diplomat. And comparing Boris/BorisD to each other, I found roughly the same amount of similarities.

Let's get a bit more accurate: I considered identical blocks showing at least 8 consecutive very same bytes (same positions of course); longer blocks being as well added to the count if all bytes but very few were same, and same position in the block. The few non corresponding bytes were of course removed from the count.

Example: s = same byte; - = different byte
----ssssssss--- value +8 (minimum block)
---ss-ssssssss-sss--- value +13 (extended block & >minimum)
---ssssss--s---sssss--- no value, so 0 (minimum not reached)

Consecutive 00 or FF were not considered.

I so found :
- 800 bytes in identical blocks comparing Delta-1 to Boris
- 808 bytes in identical blocks comparing Delta-1 to Boris Diplomat
- 871 bytes in identical blocks comparing Boris to Boris Diplomat.

Total bytes ROM count being 2006 for BorisD, 2831 for Boris, and 4096 for Delta-1:
- the Delta-1 shares 20% of its code with any of both Boris
- Boris shares 28% of its code with Delta-1, and 31% with Boris Diplomat
- The most impressive ratio is the one based on the smallest Boris Diplomat, sharing 40% of its code with the Delta-1, and 43% with the Boris.

That is common DNA, isn't it?

But a question remains pending: why is the Delta-1 so weak? (despite larger ROM, larger RAM, faster clock and later birth...)

Viele Grüße
Eric