Am I seeing 192K RAM on this Z-120 correctly?

[SouthernComputers]

Disassembling my Z-120 today, I saw it has a 85-2653-1 5Mhz model main board. From what I understand, this should have 192K total in the three memory banks. I know a later 8Mhz board model had 768K on it.

These are TMS4164-20NLJ chip, which are listed as 64kbit / 8KB chips if I read things right. Is it possible to replace these with 256kbit / 32KB chips on this 5Mhz board? And if so, does anyone know the chip number I would get? Something like TMS4256-20NL?

 

[hmb]

Disassembling my Z-120 today, I saw it has a 85-2653-1 5Mhz model main board. From what I understand, this should have 192K total in the three memory banks. I know a later 8Mhz board model had 768K on it.

These are TMS4164-20NLJ chip, which are listed as 64kbit / 8KB chips if I read things right. Is it possible to replace these with 256kbit / 32KB chips on this 5Mhz board? And if so, does anyone know the chip number I would get? Something like TMS4256-20NL?

Upgrading RAM on the original Z-120 main board involves more than just replacing the 64K RAM chips with 256K RAM chips. A kit containing the additional parts required (not including the RAM chips) was sold by a company called "FBE Research" called the ZMF-100" - it was sold back in the day to simplify the process. Contact the Z100LifeLine for information on availability and cost:

For Sale

This site is about the Heath or Zenith H/Z-100 series computer and its users.

z100lifeline.swvagts.com

An alternative would be to simply upgrade the entire mainboard to the newer 768K version - available from Z100Lifeline or alternatively https://www.retrotechnology.com/herbs_stuff/s_zenith_sales.html#z100

 

[SouthernComputers]

I appreciate your expertise. Will be looking into the upgrade kit.