The aim of these pages is to give a clear and simple set of illustrated instructions on how to upgrade your Z88 to the version 4 ROM and to 128/512Kb of internal RAM. It uses a series of photographs of my issue 4, Z88 taken with an Olympus C900 camera.
Before You start!
You should collect together all the following components before starting work:
- A medium cross-point screw driver.
- A soldering iron and a good quality, large solder sucker.
- Your new ROM, home blown, if you, or a friend have access to an EPROM blower, using the ROM image from here.
- The 512Kb pseudo-static RAM chip, (HM658512LP) usually recommended for this upgrade, is now very difficult to obtain. Fortunately, reading the Z88 hardware specification on the Z88 Forever! site and now also availabe here, as a text file, clearly states that Static RAM is not only usable, but better, as it has a much lower current consumption. I started out going for the 128K upgrade, as this works well with the original ROM, so I purchased a KM681000CLP-5L from Radio Spares (RS) on line store ( a PDF file of it's technical specification, ie a RS data Sheet is available here ). This is a CMOS, low power, 1Mb chip, organised as 128kx8 in a 32 pin DIL package, @ £2.55 plus VAT and delivery, www.rswww.com . I would recommend the 128K upgrade over the 512 to anyone who is unsure of their soldering skills, as it does not require any modification of the main board, other than the removal of one chip.
- A low profile, 32 pin DIL socket (Maplin , FZ65V, 0.79p)
