Hi and Merry Christmas,
The Gottlieb SYSTEM 1 board has been originally designed to use a P5101L-3 RAM as Z22. This chip was made by Intel.
The inscriptions on the circuits can be misleading, but we manage to decode them quite easily:
- the prefix (letters before the numbers) indicate the manufacturer (PCD for Philips, MWS for Intersil, MCM for Motorola, I or P (or nothing) for Intel.
- the suffix (letters after the numbers) indicates the sub-type (version), and the type of package.
A "P" in the suffix indicate a plastic package, a "D" indicate a ceramic package.
On Intersil, the "A" indicate an improved version (TTL compatible). The "L" was used by Intel, to indicate a version with improved retention performances (low current). But this is only specific to Intel, some other manufacturer (like Intersil) use the 51L01 designation. The model 5101L-3 has a special feature using the E2 pin to turn it into "sleep" mode, reducing the current consumption. This feature has been installed on the GTB SYSTEM 1 (section using the SCL4081).
So it is recommended to use a true 5101L RAM (or a model having the "sleep" function, selected by E2 pin).
If you found a 5101P, it's quite sure that it's a basic 5101, not a 5101L.