Gotek Floppy Emulator
With good floppy drives hard to come by, 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, REX and OS9. 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. We supply boot disk images for the GoTek, so you will need to have at least one GoTek in your system. GoTek drives are available from Amazon and sellers in China that have FlashFloppy firmware and an OLED display. You should obtain one of these drives rather than the ones with a three digit display. You have to flash the firmware in these drives and install an OLED display for these drives to be useful. Instead buy the one with a knob to select the image; it has an OLED display and the FlashFloppy firmware needed is already installed.
This is a GoTek with Flashfloppy Firmware and OLED. These units can be purchased on EBAY for under $50. Currently these units are not sold on AMAZON. The units for sale from AMAZON do not have the OLED and Flashfloppy Firmware.
You may use a real floppy drive with a GoTek should you have a need to read or write real diskettes.
VGA Video Display Card/XT keyboard
The PT68K5 supported a VGA card with the TSeng LABS ET4000 chip set. Not all VGA cards with a ET4000 chip set will work in the PT68K5. If you purchase an ET4000 video card, ensure it can be returned should it not work in the PT68K5. TSeng LABS ET4000 cards are hard to find; but should you be lucky enough to own/find one, you will still need an XT keyboard. A converter card is available to allow an AT or PS/2 keyboard to be plugged into the XT keyboard port of the PT68K5. This card plugs into the J9 connector on the PT68K5.
REX Operating System
In 2023 REX was updated to support modern hard drives. This change allows REX to have 256 16MB partitions. 16MB is the most that REX can address. REX can boot from either the main HD, the XT-IDE controller board or a floppy. REX, OS9 and SK*DOS can all use and boot from the same hard drive.
REX can be booted from the main system IDE or from the XT-IDE board.
SK*DOS Operating System
SK*DOS was never released for the PT68K5 but will be ported in the future for the PT68K5. SK*DOS will share the same 8GB space on the hard drive that REX uses. SK*DOS like REX only supports 16MB total hard drive space and can have 256 partitions. REX and SK*DOS uses the same format on the hard drive and REX and SK*DOS can read each others files. This is only useful for text files since a REX programs cannot be executed by SK*DOS.
In late 2024 SK*DOS was ported to the PT68K5. SK*DOS works like it does on the PT68K4. The PT68K4 version was modified to work on the PT68K5. VGA video boards are supported but the choice for a VGA board is the same as for OS9. VGA support requires a video board with a ET4000 chip as does OS9. SK*DOS shares the first 256 16MB partitions on the hard drive with REX. REX and SK*DOS are both bootable.
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 was 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 2021) 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 a 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 $5 for 32GB of storage space and are faster than hard drives of the 90's . The new hard disk drivers can coexist with the original drivers should you need to copy data from a old hard drive to a new one.
SD memory card to IDE converter cards cannot be used on the 16 bit internal IDE port on the PT68K5. They can be used on the XT IDE controller card.
Boot OS9, SK*DOS and REX on the same Hard Drive
As of 2025 you may boot OS9, SK*DOS and REX on the same hard drive. SK*DOS and REX will share 256 16MB partitions in the first 8GB of hard drive space. OS9 will start at 8GB and can occupy the rest of available space.
Minix
Minix is in the process of being ported to the PT68K5. Minix will boot using SK*DOS boot commands contained in HUMBUG. The Minix boot disk contains a special loader which is loaded as if it were SK*DOS. The loader then takes over and loads and starts Minix.
Manuals
Click Here for User Manual PT68K5 CD68X20 Users Manual
MONK5.pdf Monitor program for REX
REX.pdf REX Operating System Users Manual
PTBASIC.pdf BASIC User Manual - REX
OS9K5-2021.pdf OS9 Installation Information for PT68K5
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
EPROMS
PT68K5-rev6-os9.bin Copy to EPROM - U1
MONK5.V.5.06.BIN Copy to EPROM - U2
GoTek boot images
IMG.CFG Place this file on the USB stick to allow the images below to work.
OS9.68K5.VGA.Boot.28448.09.07.22.OSK.IMA OS9 Installation Disk - VGA terminal
OS9.68K5.RS232.Boot.28448.09.07.22.OSK.IMA OS9 Installation Disk - RS232 terminal
SD Card Images - Zipped
Unzip and use Image Writer to write to SD Card
OSK5-XTIDE-VGA-Partition0.zip OSK VGA boot from SD on XT-IDE board - Compressed with Express ZIP
OSK5-XTIDE-RS232-Partition0.zip OSK RS232 boot from SD on XT-IDE board - Compressed with Express ZIP
| PT68K5 | PT68K5 System Board,25MHZ 68020, 0K Memory - Very Limited availability | $599 |
| ET4000-K5 | ET4000 Video Card - Sold only with PT68K5 or recent PT68K5 purchases - Used - Extremely Limited Quantity | $149 |
| PT-XTIDE-K5 | IDE controller card, XT slot for PT68K5, Supports SK*DOS, REX and OS9 | $39 |
| 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 |
| K5-XT-AT | Plug in adapter board to convert on board XT Keyboard port to AT or PS/2 keyboard | $10 |
| Add On items - The items below are only sold at the time of purchase of a PT68K5 | ||
| MC68882 | 25MHZ Math Coprocessor for PT68K5 | $30 |
| 4MBx8/16 | 16 MB - Four 4MB 60ns 30 Pin SIMM (32MB Maximum) Sold only with PT68K5 board | $39 |
| 16MBx8/64 | 64MB - Four 16MB 60ns 30 Pin SIMM (128MB Maximum) Sold only with PT68K5 board | $69 |
| SSD HD | SSD 120GB Inland, Crucial, PNY or other major brand. SK*DOS, REX, OS9 | $59 |
| XT-IDE-REX | XT-IDE board, SD memory to IDE converter, cable, SD card with SK*DOS, REX, OS9 preloaded | $69 |
Click here for PT68K5 Brochure PT68K5 Historical Product Brochure
| OS9/68020 | Professional OS9 V2.4 for PT68K5, Includes K&R C, Editor, Assembler, Linker, BASIC and over 80 utilities | $499.00 |
| OS9/020U | 68020 Upgrade from PT68K2/4 OS9/68000 | $150 |
| OS9/Ultra | Ultra C for OS9 | |
| 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 | $25 |
| BASICSRC | Source Code for BASIC on 1.4MB Diskette | $20 |
| TETRIS | Game - Requires OS9 and ET4000 VGA | $10 |
| SCULPTOR | CloseOut - Version 1.14:6 (No support) | $50 |
| REXSRC | Source for REX Operating System | $10 |
Historical information on the CDS68020 and PT68K5
Early boards supported 2.88 MB floppy drives. The floppy controller chip, a SMC37C65+ was discontinued shortly after production of the CDS 68020 began. A few early boards had the SMC chip, but most shipped with a WD37C65 chip. The WD37C65 did not support 2.88MB drives. That is why there are references to 2.88MB drives in some of the literature. It was never fully edited out.