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CompactFlash Card Adapter Type II

An updated interface board has been developed which allows CompactFlash cards (Type I & II) or a IBM Microdrive™ to be used as a boot devices on a PC.  It takes advantage of the "true IDE" mode of a CompactFlash™ Card that allows it to operate as a true IDE hard disk drive.

The original CompactFlash Adapter (Type I) was developed in 1997 to fill a need for a rugged boot disk, that networkers (those people that put equipment in remote locations) could use to run NOS or some other network node software. Rugged power supplies and no moving parts were the two most mentioned criteria. How to store the software without a harddrive? Building an ISA bus card with a multitude of EPROM sockets was discussed. Later discussions considered flash memory and how to make a system think it was equivalent to a bootable disk drive. Advertisements and other references brought to our attention the fact that the CompactFlash™ cards for digital cameras were configured to look like a hard drive.

Reference material available at either the CompactFlash Association or San Disk web sites provided the information needed to make the card function in the IDE compatible mode.

A circuit board was laid out and manufactured and then populated and tested in a minimal 386 system. The Linux system was installed on an 8Mb card and was capable of supporting the TCP/IP stack with telnet, ftp and http server.

Why a Type II Adapter?
Shortly after the first few original Adapters were sold we started getting emails with suggestions on how to improve the product or "why didn't you do it this way"? As valid as all the comments were, none were compelling enough to trigger a new version, until this question: "Will it work with the IBM Microdrive™?" Some of these questions were coming from within IBM. We brushed up on the changing CFA specification and obtained some information from IBM regarding the implementation of DMA support.

We did a layout of a new board incorporating the changes needed for Type II cards and hopefully including all the suggestions made earlier. The Type II adapter has been tested with an IBM Microdrive™ in an IBM facility.

Kit Availability

The flash adapter board is supplied assembled. The adapter does not come with a Compact Flash Memory Card. See the Mini FAQ for additional information.
    Size: 2.6" x 3.065" x 0.5" (66mm x 77.8mm x 12.7mm)
    Mtg hole size and pattern: 0.14" (3.56mm) on a 2.3" x 2.7" (58.4mm x 68.6mm) grid
    Power requirements.
    • Voltage: +5 VDC via 3.5" floppy style power connector or the 44 conductor "2.5 in." IDE cable.
    • Current: None for the adapter, total depends on card inserted.
    IDE Interface: 40 pin 0.1" pitch IDE connector, optionally the purchaser may install a 44 pin 2mm pitch "laptop" IDE connector.
    CF socket: Type II socket with guides, no ejection button.

The price for the CompactFlash Card Adapter is:

  • $ 30 US for members of TAPR

  • $ 34 US for non-members

    + shipping/handling if applicable.
(Place Web Order)

To use the adapter, you need the following:

  • A CompactFlash™ card (size depends the OS and applications to be loaded)
  • A spare connector on your IDE ribbon cable
  • An unused power connector compatible with the common 3.5" floppy drive
  • A place to mount the card

    CompactFlash™ card:
    It is possible to operate with as little as 8Mb. Prices keep falling. Size requirements will depend on the OS (operating system). You can use any OS that will work with a standard HDD.

    IDE ribbon cable connector:

    If both the primary and slave connectors are already in use, you will need to add a secondary IDE controller. Typically your target system will not have any other HD, however your development host may already be full.

    Power connection:

    Fairly straightforward - be sure red wire is connected to pin 1. It IS possible to force the connector on backwards.

    Master/Slave selection:

    The board comes defaulted as a Master. If you want the Slave configuration, cut the trace on the board. If you want to be able to change back and forth frequently, you may solder in a two pin header.


    It is suggested that the adapter may be attached to any flat surface within the enclosure or case with double sided tape. (The heavy duty type such as used for hanging pictures etc.) Alternatively one could take a flat piece of sheet metal or thin plastic sheet and make a mounting plate to fit into a 5.25" or 3.5" drive bay.



Questions concerning the unit will be handled on the TAPR Linux Special Interest Group list. To subscribe, click here to reach the TAPR listserv web page.

Software Installation

Once you have the hardware mounted, IDE and power cables attached, it is time to load the OS. We'll use DOS installation as an example. You can use one of two methods. One is to hook up the adapter as a slave drive (requires a trace cut on the latest board revision) on a operating computer. The other is to use your target system with floppy drive attached. You will need to set the master/slave jumper on the adapter to correspond to its position within the system. If you load the software on a host system and then move the adapter to a target system, don't forget to change the jumper setting (most likely install it) to correspond to the new configuration.

First you must set the CMOS to recognize the new 'HD'. Most modern BIOS'es will autodetect the number of cylinders, heads, and sectors per track (CHS)of your CompactFlashTM memory card. If your BIOS won't autodetect, you may have difficulty finding out what the CHS configuration of your card is. You may be able to get this information from your vendor, but the quickest way would probably be to temporarily install the adapter and card in a system that has a newer BIOS.

The following table are CompactFlash Drive CMOS Setup Parameters. These are some CHS parameters known to exist for various CompactFlash Cards. Your mileage many vary. Please advise if you run into any new values we can enter into the table.

Capacity Sectors/Card Heads Sectors/Track Cylinders
2 MB 3,936 2 16 123
4 MB 7,872 2 32 123
6 MB 11,776 2 32 184
8 MB 15,680 2 32 245
10 MB 20,480 2 32 320
15 MB 29,312 2 32 458
20 MB 39,168 2 32 612
24 MB 46,976 2 32 734
30 MB 58,752 6 32 306
40 MB 78,336 4 32 612
48 MB 93,952 4 32 734

Assuming a target system with a floppy, you would simply put the boot diskette in the A: drive and boot the system. If you use a later version of DOS (6 or later?) running setup will handle all of the following steps.

  • Run FDISK to create a DOS partition and make it bootable
  • Run FORMAT C: (or other drive letter if applicable)
  • Run SYS C: (or other drive letter if applicable)
  • Copy other DOS command files and utilities needed to the 'HD'
The other OS installations have similar steps.

It has been reported that sometimes there are problems having two IDE devices on the same cable as the TAPR CF Adapter. We think this is isolated to certain versions of Linux. A look at ide.c source codes shows that there is an attempt to identify any CF cards in the system (to what purpose ?) and if found make the assumption that there will only be one device on that IDE cable. A common solution is to disconnect the other hardrives completely when wanting to try and boot off the FlashCard. If your target system needs two devices on the IDE cable, then you'll have to make changes in ide.c, rebuild the module and the kernel.

N. B.
We have seen reports of Linux fdisk making CompactFlash™ unuseable when run on a CF card connected directly with an adapter such as the TAPR CFA. This information dates to pre 2.x.x versions of the kernel. We've seen no details concerning version of fdisk or brand/size of CF card involved. We can only report that we've not had a problem here or received such a report from any purchasers of the TAPR CFA.

Mini FAQ

  • What is it? A small circuit board which has a socket to accept a Compact Flash&trade memory card. It also has an IDE drive connector and power connector.

  • What does it do? It allows one to build a diskless PC system. The Compact Flash card provides 100% hard drive emulation.

  • How do I use it? You plug in power and IDE cables from your PC and plug in a Compact Flash card. Initialize the Compact Flash card and install the operating system just as you would a regular hard drive.

  • What operating systems may I use? Both Linux and DOS 6.22 have been tested. The only theoretical limitation is the Compact Flash card capacity. E. g. Windows 95 wouldn't fit on a 8Mb Compact Flash card.

  • Where do you get the Compact Flash card? At any store that carries digital cameras or digital camera accessories.

  • Where do you get the flash adapter? See the TAPR order page.

Other Links

Please advise us of changes.

The CompactFlash Association web has some good information as well as links to sites of manufacturers who make the cards and related products.

Linux has been used in the preliminary testing of the concept. It will probably remain the OS of primary interest for the this project. We were unaware of the work being done by the Linux Router Project at the time we started on ours. However, one may find their web site to be an interesting reference. Recently we have become aware of the FREESCO project, which may have potential. It is a floppy based system, but there is a utility to transfer the floppy system to a HD. It lacks AX.25 support in its present version.

CompactFlash Card

The TAPR Adapter uses CompactFlash Cards. There are several manufacturers of the memory. The one used in the prototype testing was a Hitachi HB2860008C2.

The photo (right) is of the San Disk CompactFlash card.

Prices continue to drop, so shop around.


CompactFlash is a trademark of the SanDisk Corporation.
Microdrive is a trademark of IBM.
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