Pictures and history of the Chaos Computer – “The computer described on these pages was started in 1977 with the gift of a Signetics 2650 microprocessor by Mullard. Attempts during the previous year to order an Intel 8008 and a 2650 from Farnell had all proved impossible, and this 2650 processor was finally obtained after my father drafted me a letter which I sent to the Managing Director of Mullard. The 2650 was an 8 bit processor with 32Kbyte address range and 256 I/O locations. It has 7 general purpose registers and an on-chip return address stack for subroutines with 8 entries. It was not possible to make data access to this stack or flush it to memory. “ – Link.
The Chaos computer