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Choosing a memory chip that works with the Z88 is important. Manufactures and the availability of chips change. See Memory Chips for the most 'up-to-date' results.
RAM chips
There are 3 types of RAM chips that may be used either Internally or Externally.
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There are some RAM chips that according to the application or data sheets should work, but don't. They are only found by trying them and the reason why they don't work will remain unknown.
PCB Footprint Converters
To aid construction, these converters may be used to allow the new surface mount devices to be used as larger devices. Let's face it, DIL or DIP packages are a lot easier to handle and solder. These converters may be used to 'bridge that gap.' Here are some examples:-
Internal or External?
Changing the RAM or the ROM inside the Z88 is a time consuming and skilled operation. Unless the user has good soldering experience, changing chips in a 25-30 year electronic device can lead to killing the Z88 altogether. Let's look at the advantages when a successful conversion has been achieved first.
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Leaving the Z88 alone and using the external cards have quite unexpected advantages (apart from being a lot easier). The first thing the Z88 does when given a HARD RESET is to go to Slot 1 to see if there is a copy of OZ to run from there. If that happens, the program will not access the internal ROM thus putting in into standby mode.
External RAM (fitted in the card slot)
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Memory prices have fallen since then so this is more attractive now to go for the largest card available.
1M RAM
Picture | Device | Operating | Standby |
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CYPRESS SEMICONDUCTOR - CY62158ELL-45ZSXI - SRAM, 8MBIT, PARALLEL, 45NS, 44TSOP This memory chip is being used in the Rakewell's Flash/RAM card successfully. TESTED OK Datasheet | 1.8 mA | 2uA | |
BSI (BRILLIANCE SEMICONDUCTOR) - BS62LV8001EIP55 - IC, SRAM 8M, 1024KX8, 2.4-5.5V, SMD This memory chip has been used in the Rakewell's Flash/RAM card successfully. TESTED OK This part is no longer manufactured. Datasheet | 10mA | 3.5uA | |
ALLIANCE MEMORY - AS6C8008-55ZIN - SRAM, 8MB, 2.7-5.5V, 1024KX8, TSOP44 TESTED FAILS |
LYONTEK - LY62W10248ML-55LLI - SRAM, 8M, 1MX8, 2.7-5.5V, 44TSOPII This memory chip is a 'drop-in' replacement for the BSI chip (see below). TESTED FAILS when loading a file in PipeDream. |
512K RAM
512Kb Cartridge for Z88 | |
ALLIANCE MEMORY - AS6C4008-55SIN - SRAM, 4MB, 2.7V-5.5V, 512KX8, SOP32 Note: This has not been tested. It will probably fail. |
Internal RAM (fitted on the Motherboard)
The internal 32K of RAM is not large enough. Upgrading this to 128K or 512K internally is possible, but the original 'built-in' OZ operating system did not use this correctly.
Cambridge Computer commissioned OZ 4.0 ROM and were planning to use this with the new User Guide v3 but only the User Guide was changed. The new ROM was made available to users through the Z88 User Group.
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Note: On this motherboard the RAM socket is a 24 pin which is big enough for 32K. Later versions had a 28 pin fitted.
512K RAM
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Z88 32kb to 512kb Memory Upgrade
Original Article by Don Walterman
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Wide internally your Z88 to 512Kbytes
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Picture | Device | Operating | Standby |
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32K RAM Standard in Z88 NEC 42832 32k x 8 Pseudo Static RAM 150 mS Datasheet | 1 W 200mA | 2.8 mW | |
HITACHI HM658512LP-12 4Mb PSRAM HM658512 (250mW active) TESTED OK by Benny This part is no longer manufactured. | 75mA |
2mA | |
CYPRESS-SEMICONDUCTOR-CY62148ELL-55SXI-IC-SRAM-4MBIT-512KX8-5V SOIC32 |
20mA |
3.5uA | |
TESTED OK by Patters . Datasheet. | 30mA | 4uA | |
ALLIANCE MEMORY - AS6C4008-55SIN - SRAM, 4MB, 2.7V-5.5V, 512KX8, SOP32 This has not been tested yet. | 30mA | 4uA |
128K RAM
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Picture | Device | Operating | Standby |
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ALLIANCE MEMORY - AS6C1008-55PCN - SRAM, 1MB, 2.7V-5.5V, 128KX8, PDIP32 This has not been tested yet | 10mA | 1uA |
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