| Processor | CMOS Z80 running at 3.2768 Mhz. |
| Circuitry | Most complex jobs are done by the BLINK gate array chip. |
| Memory | The Z88 can address up to 4M of memory. This is achieved by dividing the 64K address space of the Z80 processor into 4 x 16K segments. Each segment can then be assigned to any of 256 x 16K banks, thus allowing a total of 4M. The first 64 banks are assigned to internal memory and the three card slots at the front of the machine are assigned 64 banks each. |
| RAM | 32K internal, expandable by addition of external RAM cards. 512K RAM may be soldered as internal RAM replacing the 32K standard (requires also retracking of circuitry). Current available are 128K, 512K and 1MB RAM cards. |
| ROM | 128K internal (some Z88 portables have pre-fabricated ROM chips, most others use a 128K EPROM), but also bootable by inserting Eprom or Flash Card with OZ image in slot 1. ROM by definition contains the operating system (OZ), built in applications and hooks for external applications to be integrated into the system. The underlying hardware allows the internal ROM to be expanded to 512K. However, modification of the motherboard is needed to add the extra address lines, since only 128K is addressed. |
Screen | 640x64 pixels, usually divided into 104x8 6 pixel wide characters and 16x64 pixels of status information at the far right of the screen. |
Serial Port | RS232 port, configured as DTE, for connecting a printer or communicating with other devices. Tx, Rx, CTS, DCD and RTS can be independently set and read, both software and hardware handshaking are supported. The serial port runs at the following baud rates: 75, 300, 600, 1200, 2400, 9600, 19200, 38400. |
Power supply | Internal batteries (4xAA, alkaline) or external 6.5V DC supply. Note NiCad's are not suitable, losing their charge too quickly at the end of their life, thus putting data at risk. Also even if the Z88 is running off the power supply, batteries should be installed. This safeguards against power failure etc, which may cause data to be lost in a machine with no batteries. |
EPROM/Flash Cards | Slot 3 contains circuitry for programming EPROM cards. This circuitry unfortunately means that RAM cards in slot 3 consume much more power than in slots 1 and 2. It is recommended that slot 3 is, therefore, not used for RAM. Note also that when the machine is powered up from cold (eg. for the first time) there is a small chance that an EPROM in slot 3 will be written to and corrupted. Therefore, it is advisable to remove EPROMs if the Z88 has had no power and you are about to apply it. 32K, 128K and 256K EPROM Cards are available. Rakewell supplies 1Mb Flash cards that may be updated in all slots (including erasing/formatting). Intel 28F generation Flash cards may be programmed and formatted in slot 3 only. AMD 29F generation flash cards may be formatted and programmed in all slots (including slot 0). |
Software | OZ operating system. Index (application coordinator), Filer (RAM filing system), Panel (for system settings), PrinterEd (for printer settings), Imp Export (for communication with other machines), Terminal (VT 52 compatible), Alarm, Clock, Calendar and Calculator. Also three fully blown applications: PipeDream (wordprocessor and spreadsheet), Diary and BASIC (a version of BBC BASICZ80). V4.5 OZ is added with EazyLink (remote file management from other computers), XY-modem protocol in Imp/Export and FlashStore (file backup/management on Flash/Eprom File Cards). |
Expansion | Three card slots at the front of the machine for RAM or EPROM/FLASH Cards. Expansion connector available for OEM applications, but is normally sealed. |
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| Awake | Z80 clock running and display on. |
| Snooze | Z80 clock stopped and display on, ie. waiting for keyboard activity. |
| Doze | Z80 clock running and display off, ie. programming EPROM .and Flash cards |
| Coma | Z80 clock stopped and display off, ie. machine shut down. |
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| :RAM.n | File device in slot n, 0=internal, -=virtual (all RAM available). Read and write. |
| :INP.0 | Standard input device, usually the keyboard, but can be redirected. Read only. |
| :OUT.0 | Standard output device, usually the screen, but can be redirected. Write only. |
| :SCR.0 | The screen. Write only. |
| :COM.0 | The serial port. Read and write. |
| :PRT.0 | The printer. Data sent to this device is processed by the printer filter whose settings are defined by the PrinterEd application. Write only. |
| :NUL.0 | This device does nothing, but can be useful when you want to send something nowhere, or get nothing from anywhere. Data sent is thrown away, reading returns an End of File message. Read and Write. |
| :ROM.n | Associated with application in slot n, 0=internal. This device can be read using the DOR routines described later, but cannot be used as a conventional device. :ROM.0 device is not available when OZ is running in slot 1 (in effect overriding slot 0 applications). |
| :APP.- | Virtual slot associated with application installed in RAM (OZ 4.5 and newer). |
Streams and Filters
A stream is simply a communication channel associated with a handle. Various system calls can take input or send output to a stream. For example the system routine to convert binary to ASCII decimal numbers can direct its output to the standard output stream rather than store the result in a buffer in memory and then output the contents of that buffer as a string. A filter is a general way of performing simple transformations on character sequences. Text can be sent to a filter and then pulled out again, having been processed according to the set of transformations associated with the filter. Some system routines take a filter as their input, requiring the application to have already sent text to the filter, and others as output, requiring the filter to be read after the routine is complete.
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V4.0 of the OZ operating system automatically recognises the machine as expanded if the Z88 has been upgraded with 128K or more of internal (slot 0) RAM (replacing the original 32K RAM chip). However this requires soldering work on the motherboard. The V4.2 and newer releases of the OZ operatiing system also sets the expanded machine state if 128K or more RAM is inserted in slot 2.
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