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.

Two small expansion boards are available that provide either two 1.44MB Floppy drives or USB connections; a LAN connection is available on both adapters.

NEW!!!  The SmallZ80 has a new CPU: the SmallZ-180 adapter.  It replaces the Z80 CPU with a Z8S180 CPU, running a 22.1148MHz clock in DoubleSpeed, operating the CPU at 44.2368MHz.  It carries 1MB of RAM and a 32K EEPROM. Taking orders now! (The original SmallZ80 is required as a base for the new CPU.)


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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.

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Heath H89

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


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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. 

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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.


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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.


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Production Status and What's New

10 July 2023: New BETA EEPROM and CF for SmallZ180.

4 Mar 2021: Updates for the EEPROM and CF images (both Z80 & Z180) are posted.

21 Feb 2021: Updates are posted for the SmallZ80 & Z180 EEPROM, Compact Flash images for Z80 & Z180, and an updated user Manual.  See the SmallZ80 Downloads page.

27 Dec 2020:  We're taking orders on the Z180 Upgrade.  The IO Map upgrade is required.

7 Nov 2020: The SmallZ80 I/O map upgrade is posted in the Download area.  It provides a complete CF image and the binary files for EEPROM, SMZ-Gide-2, and the system I/O Map Decoder.  The SmallZ-180 testing is complete; software is in development.

5 Aug 2019: Many updates for the SmallZ80: New CF-IDE image, new EEPROM files, and new User Manual!

11 Mar 2019:  SmallZ80 services/prices updated.

6 Mar 2019:  New SmallZ80 v2 CF and EEPROM downloads are posted.  One of our customers has posted a 6-minute introductory video of the SmallZ80 in action.  See it on YouTube here.

17 Dec 2018:  Updated SmallZ80 User Manual posted.

9 Dec 2018:  Kits are shipping now!  New images posted on SmallZ80 Photos.  New SmallZ80 User Manual, CF image, and Distribution EEPROM v1.00 posted in Downloads.

15 Nov 2018:  New User Manual and EEPROM image posted.  PCB design is final; PCBs will be ordered on Thursday, 22 Nov.  We're taking orders now see the Services and Prices page.  The format review of the pre-production unit is posted here

14 Nov 2018: New SmallZ80 User Manual, Disk Image, and EEPROM source code posted in preparation or ordering production PCBs.  New information post on the Update Log.  Kit & assembly prices are now posted here.

10 Oct 2018:  New SmallZ80 User Manual posted today.

9 Oct 2018:  The SmallZ80 is nearly ready for production.  The final PCB design is ready and should be in production in the next 2-3 weeks.


Old Stuff:  Our P112 offerings of  D-GIDE and XPORT LAN Adapters are still on-hand.  The H89 D-GIDE + RAM is still available.  The original Stack180 is out of production, but the new V2 system is ramping up.  The 'Mini' version of the system is available now in prototype PCB format.