The SmallZ80 is a small, single board system with a 20MHz Z80 CPU, 576K of RAM (512K Banked), an IDE interface, a Real Time Clock with battery backup, and a two serial ports that can provide LAN access for terminal and printer I/O.  The design is stable and ready for production. Still in the development stage, the Boot/Monitor ROM and CP/M operating system are up and running with a full complement of Z-System components and utilities.

A small expansion board is being tested that provides two 3.5" 1.44MB floppy drives and 2 serial ports.


The Stack180 is a new system, designed around the Zilog Z8S180-33 CPU.  The system is designed with a 'modular' approach, consisting of a three-board set.  The first board, the CPU, can operate alone, or in conjunction with the Dual GIDE.  The Dual GIDE requires the CPU board, and provides a mount point for the Mainboard, adding significant I/O capabilities to the system.

A fully-capable CP/M system requires the CPU and Dual GIDE.  Two versions of CP/M are available: B/P BIOS and StackOS.  Both OS models are based on the Z-System, with ZSDOS and ZCPR 3 providing the BDOS and CCP.

B/P BIOS includes a banked OS that includes advanced memory management and banking to provide a large TPA with a wealth of options that would otherwise result in a much smaller TPA.  Disk I/O is limited to the one of the two IDE adapters on the D-GIDE, providing a Master and Slave IDE configuration, as well as up to four floppy drives in nearly any configuration (3.5", 5.25", or 8".)

The StackOS is partially banked; the TPA is not as large as that provided by B/P BIOS, but it provides a wider range of hardware drivers and better compatibility with standard CP/M.  In addition to the IDE and Floppy drivers handled by B/P BIOS, you can also drive the second D-GIDE adapter as well as one or two 16-bit AT-Style adapters installed in one or two of the 16-bit AT slots.  Drivers for a ZIP-100 drive, RamDisk, and 64K Printer Buffer are included.

The Stack180 hardware design is complete; the software is still undergoing development.  At present, both OS models are boot-capable and fully operational.

Heath H89

The new Heathkit H89 Dual GIDE is in production.  The H89 page gives some specifics of the new adapter.



The P112 single board computer was designed by David Brooks and was last available in kit form in 1996.  In 2004, David Griffith made arrangements to issue new P112 kits.  Three 'Beta' kits were assembled and debugged in late 2005, and new software development efforts began.

The original operating system software is still available here.  It includes all source code for the ROM, BIOS, and a few utilities.

The new system software can be downloaded here.  Included is a fully-configured Z-System with ZSDOS, ZCPR3, all source code, and numerous Z-System utilities. The only configuration item still necessary is to define your terminal capabilities with a Z3TCAP file.  The downloaded file is an image of the system disk; DD.EXE is used to write the image to a formatted floppy (also available here.)

A new run of P112 kits (Jan 2013) is being produced by David Griffith.  Deliveries should start soon.  Our P112-GIDE kit is ready to ship.  We've also added a new adapter kit to our P112 offerings: the 4-Port LAN adapter.  It provides a hardware path for integrating your P112 into your LAN system.  The new crop of P112's will be delivered with the EEPROM already coded to allow the P112 to make use of a LAN-based terminal. 


The original GIDE (Generic IDE) interface was designed by Tilmann Reh of Germany.  This webpage contains the latest information.  The GIDE added 16-bit IDE disk I/O capability to a generic Z80-based computer.  The P112-specific version described here does the same thing, but is specifically designed to accommodate the expansion connector and mounting holes of the P112 and the Z80182 CPU.  It provides 16-bit I/O to your 'typical' IDE drive, along with the software necessary to format and partition the drive.  Also included is Hal Bower's B/P BIOS, a Banked and Portable BIOS that can make use of the entire 1MB address space of the P112.  With the current-version ROM and B/P BIOS, the GIDE is the primary P112 cold-boot device.

The P112-GIDE has also been tested satisfactorily with a 128MB Compact Flash-IDE adapter in place of a hard drive, and is maybe a little faster.  A 64MB Compact Flash module is recommended; larger is OK, but probably unnecessary.  A second CF adapter can also be used in a master-slave configuration.

A dual-GIDE adapter setup has been configured and tested.  The BIOS does not support a secondary adapter, but certain utilities do.  The CDZSWP program has been modified to allow reading/copying CDROM contents via the secondary adapter, and a BACKUP/RESTORE program is being written to copy/restore the primary Master to/from the secondary Master or Slave.  The primary Slave device can also be used for backup purposes.


P112-4 Port LAN

The 4-Port LAN adapter requires the P112-GIDE.  Once installed, you can immediately begin using your LAN-connected PC as the P112's terminal display.  The LAN adapter can connect to four LAN-based devices, including printers and other CP/M machines.  This photo shows the final prototype.


Production Status and What's New

UPDATE - 7 Oct 13:  P112 kits are being delivered now.  We're shipping P112-GIDE and 4-Port LAN kits regularly.  We should have several P112 kits on hand for assembly by the end of the week.  Another set of P112 software is posted for download, including Floppy and CF images as well as the EEPROM .BIN and .HEX files.

A new StackBP image has been posted.  Similar to the StackOS image pasted last month, the B/P image requires the use of Win32 Disk Imager to write the contents to a CF module (minimum 128MB.)

David Griffith is bringing out a new run of P112 kits.  We have P112-GIDE PCBs in stock and will ship when the P112 kits start shipping.  We offer a 'build and configure' service for those that don't want to deal with the assembly and testing of the P112 and GIDE.  Basically, you order the P112 kit from David, have it shipped here, and we'll perform the build and testing, then ship it to you.  We are also happy to provide the same service for our P112-GIDE kit.  See the P112 Services page.  We also have the new P112-4 Port LAN, described above.  The EEPROM used in the new run of P112 kits is already capable of using the 4-PORT LAN adapter for Terminal I/O.

The latest EEPROM code (2.04.01 of 09-09-12) and Stack180 User Manual (12 Sept 2012) are posted in Downloads.

The old (but still current) P112 Boot Disk image of 07Jul06 has been re-posted in the P112 Downloads.

A new Stack-180 EEPROM file is in the download area (Version 2.02.05 of 20 Feb 2012).

The latest User Manual (12 February 2012) is posted, and new system images for StackOS and StackBP.

A new StackOS image has been posted.  This is primarily for publishing the latest version of BACKUSB, now referred to as BACKUP. 

The Heathkit H89 Dual GIDE adapter is shipping.  See the H89 page.

The StackOS now supports LAN-based printer output, along with the LAN-based Terminal I/O.

The XPORT and LCD Display Adapter is available for ordering.  The adapter provides serial access to the XPORT for serial recovery, an 8-bit LED display, and a 24 character x 2 line LCD display unit.  The EEPROM and StackOS support updates for the LCD Display are posted.

A 2MB RAM expansion kit is now available.  The latest EEPROM can detect and test the RAM expansion; the StackOS BIOS contains a 1MB RamDisk driver for it.