The PT68K2 will boot into the HUMBUG monitor on power-up. From the HUMBUG monitor you may either boot SK*DOS or start the MONK monitor (REX operating system) or OS9 boot menu. Each monitor has commands to select the other monitors. SK*DOS, REX and OS9 all share the same SD card. SK*DOS and REX use a near identical disk format and share the first 256 partitions on the SD card. SK*DOS and REX can read and transfer files between partitions but executable files are not interchangeable. A SK*DOS program will not work in REX or vice versa. OS9 occupies the space after the partitions reserved for SK*DOS and REX to the end of the SD card.
GoTek Floppy Emulator
With good floppy drives becoming difficult to find, to say nothing of blank diskettes, an alternative is needed. A GoTek drive with Flashfloppy Firmware update is capable of reading and writing disk formats as used by SK*DOS and REX. The GoTek uses USB memory sticks to store images of floppy disks and can hold thousands of disk images on a single USB stick. The images can be emailed as well as downloaded over the internet.
A GoTek allows users to download DSK image files from the internet, and there is a PC utility program to convert these image files to .IMA format used by the GoTek unit. Originally GoTeks had to have their firmware reflashed with Flashfloppy firmware, and it was necessary to add an OLED screen in order to tell which image you selected and to see error messages. It is no longer necessary to buy a GoTek and immediately modify it. Fortunately you can purchase ready to use GoTeks. GoTeks are now available with FlashFloppy firmware and OLED displays; in addition, they use a rotary knob to select images. This is a big improvement over the up and down push buttons on the original units.
This is a GoTek with Flashfloppy firmware and OLED. These units can be purchased on EBAY for around $55. Recently there is a single seller on AMAZON but at greatly higher cost. Most of the GoTek units for sale on AMAZON do not have the OLED and Flashfloppy firmware and should be avoided since they need to be modified.
You may use a real floppy drive with a GoTek should you have a need to read or write real diskettes.
SK*DOS
The Humbug Monitor will support RS232, Monochrome, CGA and some ET4000 based VGA boards. You will end up using a 16 bit card with one of the connectors not plugged into a connector. With the optional HD floppy controller all disk sizes between 320K and 1.4MB are supported. Hard disk support is by the PT-XT-IDE
Minix
Minix can be downloaded from the FLEX users group FTP site. Minix is booted from the HUMBUG monitor.
REX
Rex will support RS232, CGA, EGA and VGA. The list of EGA and VGA cards supported has been lost. All CGA cards should work but only VGA cards containing a ET4000 chip will work and not all cards containing a ET4000 will work. Rex will support floppies from 320K to 1.4MB. 1.2MB/1.4MB requires the use of the FD-3765 HD floppy controller. Hard disk support is the PT-XT-IDE controller.
OS9
OS9 hard disk drivers have been updated to support modern IDE drives. The original hard disk drivers don't work reliably with today's hard drives. The set parameters command doesn't seem to work well with drives that were made in the last 20 years, The IDE drivers were updated to support LBA mode of today's IDE drives. Older IDE drives that do not support LBA modes cannot be used.
A new (updated in 2024) OS9 Boot ROM is supplied. This ROM supports booting OS9 from modern drives and different partitions. This includes mechanical HD's, SSD, SD memory cards and compact flash memory. While we suggest 4MB partition sizes, partition size can be up to 8GB. This is possible because IDE drives use 512 byte sector sizes. Devices that use a 256 byte sector size will support 4GB partition size. The ROM update also allows booting from an XT IDE controller card. It is assumed that the XT IDE controller would be connected to an SD to IDE converter card and use SD memory cards. This is intended to provide for an easy and cheap backup of an SSD hard drive on the 16 bit internal IDE port. SD memory cards are readily available for about $10 for 32GB of storage space and are faster than hard drives of the 90's .
Hard Disk support for IDE drives for REX, SK*DOS and OS9
The PT-XTIDE controller card supports REX and SK*DOS and OS9.
Revised Boot EPROM
The Boot EPROMS were revised in December of 2024 to allow HUMBUG, MONK and OS9 to be located in the same EPROM. Prior to the update you had the choice of HUMBUG or MONK with the ability to jump to the OS9 boot menu. Now HUMBUG, MONK and OS9 are all contained in a pair of EPROMs. VGA support was added for HUMBUG. On power-up the system will start in HUMBUG, from HUMBUG you can jump to MONK or the OS9 boot menu.
Downloads
Click here for PT68K2 Brochure PT68K2 Historical Product Brochure - The address and telephone number are not valid.
68000 Hardware Manual.pdf This manual is a combination of the Radio Electronics Articles and a course taught by Peter Stark using the PT68K2.
EPROMS, PAL
This EPROM set contains HUMBUG, MONK and OS9. You need two 27C512 EPROMs.
U20 Can be used in the PT68K4 (U27)
U27 Can be used in the PT68K4 (U26)
Minix Boot is supported in the HUMBUG monitor
Manuals
SK*DOS
Humbug_68K_1987.pdf Humbug Users Manual
SK_DOS_68K_Users_Manual_1988.pdf SK*DOS Users manual
68000 Hardware Manual.pdf This manual is a combination of the Radio Electronics Articles and a course taught by Peter Stark using the PT68K2.
REX
MONK5.pdf Monitor program for REX
REX.pdf REX Operating System Users Manual
PTBASIC.pdf BASIC User Manual - REX
OS9
OS9 - 68K V2.4 Users Manual.pdf
OS9 - 68K V2.4 Technical Manual.pdf
OS9 - 68K V2.4 Technical IO.pdf
OS9 - C V3.2 Release Notes.pdf
Software
SD Card Image - Zipped
UnZip the image and copy the image to a SD card. One program that will copy from a file to SD is Win32DiskImager. It can be obtained here - https://win32diskimager.org/ . The format of the SD card is not compatible with a PC. The file contains a raw image that is written to the SD card starting with LSN 0. The resultant SD card does not have a PC compatible file structure. You cannot examine the SD card using file manager on your PC. Your PC may even prompt you to format the SD after imaging the SD. Don't format it. The SD is ready for use in your PT68K2/4 system.
When inserting an unformatted SD or one that has been imaged before your PC will ask it you want to FORMAT the SD. Don't FORMAT, ignore all the warnings and start Win32DiskImager.
The image contains bootable copies of SK*DOS, REX and OS9 and must be used with the updated EPROMs listed above.
GoTek Images - Historical Copies from the 80's - Does not support the PT-XT-IDE Controller
Click here for PT68K2.Boot.SKDOS.IMA GoTek image file for SK*DOS - boots on 1772 Floppy controller
PT68K2/3765.Boot.SKDOS.IMA GoTek image file for SK*DOS - boots on 3765 Floppy controller
On Board WD1772 floppy controller
Recently the WD1772 floppy controller chip has become difficult to find and is very expensive when you can find them. Assembled boards ship without the WD1772 installed and include the FD-3765 high density floppy controller card.
| PT68K2-10 | PT68K2 System Board 10 MHz - Assembled with 1MB 100ns memory, No WD1772 installed, included FD-3765 | $399 |
| PT68K2-12 | PT68K2 System Board 12.5 MHz - Assembled with 1MB 100ns memory, No WD1772 installed, includes FD-3765 | $450 |
| PT68K2-Bare | PT68K2 Board - Bare | $59 |
| PT-XTIDE-K2 | IDE controller card, XT slot for PT68K2, Works with SK*DOS, REX or OS9 | $39 |
| PT-XTIDE-K2-32GB | IDE Controller with SD memory to IDE adapter,32GB card, SK*DOS, REX and OS9 Preloaded | $59 |
| WD1772 Chip | Chip is difficult to find - Expect prices to be from $50-$100 - email for availability and price | |
| K5-RS232/VGA/KBD | Use a VGA monitor and PS/2 keyboard on one of the RS232 Ports | $33 |
| K5-RS232/VGA/USB | Use a VGA monitor and USB keyboard on one of the RS232 Ports | $33 |
| FD-3765 | High Density floppy controller ,Plugs in XT slot uses 3765 controller chip | $30 |
| OS9/68020 | Professional OS9 V2.4 for PT68K5, Includes K&R C, Editor, Assembler, Linker, BASIC and over 80 utilities | $299.00 |
| SK*DOS | SK*DOS Operating system | $99 |
| REX | REX Operating system, supports VGA - Free - sold for $10 to cover copying manuals and disks | $10 |
| CLIBV3.2 | C Graphics Library for K&R V3.2 (Includes Source) | $50 |
| CLIB-ULTRA | C Graphics Library for Ultra C (Includes Source) | $50 |
| BASIC | BASIC for REX Operating System | $10 |
| BASICSRC | Source Code for BASIC on 1.4MB Diskette | $20 |
| SCULPTOR | CloseOut - Version 1.14:6 (No support) | $50 |
| REXSRC | Source for REX Operating System | $10 |