The cartridge that came with the ESQ1 from the factory in the '80's was either an EEPROM or ROM type. The EEPROM was reprogrammable (2864 or 28C64) and one could load either a single program (patch) or a whole 40 page bank at one time from the ESQ1 or SQ80. The ROM version (2764 or 27C64) was factory programmed and couldn't be changed.
This is the schematic of the stock EEPROM cartridge
Below are the card edge pin connections
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
| A0 | A2 | A1 | A3 | D0 | A4 | D1 | A5 | D2 | A6 | D3 | A7 | D4 | A8 | D5 |
| 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 |
| A9 | D6 | A10 | D7 | A11 | /OE | A12 | N/C | /CPRES | N/C | Vcc | GND | WR | GND | /CE |