/* Imported from Wayback Machine
   Original URL : https://retrobrewcomputers.org/doku.php?id=boards:isa:xt-fdc:start
   Snapshot date: 2025-12-08
   Generator    : wayback-archiver
*/

==== Table of Contents ====

[[#isa_xt-fdc|ISA XT-FDC]]

[[#introduction|Introduction]]

[[#hardware_documentation|Hardware Documentation]]

[[#build_information|Build Information]]

[[#vintage_computer_forum_links|Vintage Computer Forum Links]]

[[#bios_links_files|BIOS Links & Files]]

[[#parts_list|Parts List]]

[[#jumper_settings|Jumper Settings]]

[[#alternate_controller_chips|Alternate Controller Chips]]

[[#known_problems_issues|Known Problems/Issues]]

[[#builder_s_notes_comments|Builder's Notes/Comments]]

[[#photo_gallery|Photo Gallery]]

[[#file_list|File List]]

====== ISA XT-FDC ======

{{https://retrobrewcomputers.org/lib/exe/fetch.php?w=640&tok=dff41d&media=boards:isa:xt-fdc:xt-fdc-components.png?640}}

===== Introduction =====

The XT-FDC is an 8 bit ISA board based on the National Semiconductor PC8477B floppy disk drive controller chip, a chip that supports up to four floppy disk drives. It supports up to four floppy drives internally with an optional external connector for two of those.

Hardware functionality included is:

Basic FDC.

Configurable IO ports, interrupts, and DMA.

Optional boot ROM.

Optional ROM drive. **(As of May 2013: No supporting software - none currently planned).**

Optional connector for external floppy drive (self-powered).

Optional use of a DP8473V controller chip in socket U2 instead of a PC8477B controller chip in socket U16.

Optional use of an 82077AA controller chip in socket U16 instead of a PC8477B. **(See 'Known Problems/Issues' section below.)**

Optional connector for 8“ drive (no guarantee of suitability).

This board was a project on the Vintage Computer Forum, and a large amount of useful information can be found in forum threads there. See the links in the “Build Information” section below to relevant threads on this forum.

===== Hardware Documentation =====

Current Version: XT-FDC Rev 01

[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:printing_xt-fdc-brd.pdf|Board: printing_xt-fdc-brd.pdf]]

[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:printing_xt-fdc-sch.pdf|Schematic: printing_xt-fdc-sch.pdf]]

Manufacturing Files: {{[[lib:images:smileys:fixme.gif|FIXME}}]] Files were not on old wiki {{[[lib:images:smileys:fixme.gif|FIXME}}]]

[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:isa_xt-fdc-001.zip|KiCAD Files: isa_xt-fdc-001.zip]]

===== Build Information =====

==== Vintage Computer Forum Links ====

Note - the Vintage Computer Forums moved to a new URL in February 2016. All links below point to the new URL.

[[http://www.vcfed.org/forum/showthread.php?32476-XT-FDC-Rev1|VCF XT-FDC Rev 1 "Wiki" Page]]

[[http://www.vcfed.org/forum/showthread.php?32466-XT-FDC-project-level-of-interest|VCF XT-FDC Main Thread]]

[[http://www.vcfed.org/forum/showthread.php?44247-Sergey-s-8-Bit-FDC-and-Serial-Port-board|VCF Thread w/BIOS feedback]]

==== BIOS Links & Files ====

The BIOS for the XT-FDC has been written by Sergey Malinov. The latest version may be found [[http://www.malinov.com/Home/sergeys-projects/isa-fdc-and-uart|here]] in case the files below are out of date. (Note that the linked page is for a different hardware board than the XT-FDC; the BIOS works with both boards).

[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:floppy_bios-2.2.bin|XT-FDC BIOS 2.2 - Binary]]

[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:floppy_bios-2.2.tar.gz|XT-FDC BIOS 2.2 - Source]]

==== Parts List ====

[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:xt-fdc.lst|Parts List]]

==== Jumper Settings ====

The diagrams below document the jumper settings for the XT-FDC board. Click for larger images. Diagrams courtesy of http://www.minuszerodegrees.net/

**Basic FDC:**\\
[[https://retrobrewcomputers.org/lib/exe/fetch.php?cache=recache&tok=59ddfe&media=http%3A%2F%2Fwww.minuszerodegrees.net%2Fxtfdc%2FXT-FDC%2520-%2520jumper%2520configuration%2520-%2520FDC%2520configuration.jpg|{{https://retrobrewcomputers.org/lib/exe/fetch.php?w=300&cache=recache&tok=d8d809&media=http%3A%2F%2Fwww.minuszerodegrees.net%2Fxtfdc%2FXT-FDC%2520-%2520jumper%2520configuration%2520-%2520FDC%2520configuration.jpg?300|www.minuszerodegrees.net_xtfdc_xt-fdc_20-_20jumper_20configuration_20-_20fdc_20configuration.jpg}}]]

**Boot ROM:**\\
[[https://retrobrewcomputers.org/lib/exe/fetch.php?cache=recache&tok=49843e&media=http%3A%2F%2Fwww.minuszerodegrees.net%2Fxtfdc%2FXT-FDC%2520-%2520jumper%2520configuration%2520-%2520boot%2520ROM.jpg|{{https://retrobrewcomputers.org/lib/exe/fetch.php?w=300&cache=recache&tok=59de88&media=http%3A%2F%2Fwww.minuszerodegrees.net%2Fxtfdc%2FXT-FDC%2520-%2520jumper%2520configuration%2520-%2520boot%2520ROM.jpg?300|www.minuszerodegrees.net_xtfdc_xt-fdc_20-_20jumper_20configuration_20-_20boot_20rom.jpg}}]]

**ROM Drive:**\\
[[https://retrobrewcomputers.org/lib/exe/fetch.php?cache=recache&tok=55fb5a&media=http%3A%2F%2Fwww.minuszerodegrees.net%2Fxtfdc%2FXT-FDC%2520-%2520jumper%2520configuration%2520-%2520ROM%2520drive.jpg|{{https://retrobrewcomputers.org/lib/exe/fetch.php?w=300&cache=recache&tok=3f60e2&media=http%3A%2F%2Fwww.minuszerodegrees.net%2Fxtfdc%2FXT-FDC%2520-%2520jumper%2520configuration%2520-%2520ROM%2520drive.jpg?300|www.minuszerodegrees.net_xtfdc_xt-fdc_20-_20jumper_20configuration_20-_20rom_20drive.jpg}}]]

**DP8473V in socket U2:**\\
[[https://retrobrewcomputers.org/lib/exe/fetch.php?cache=recache&tok=e1c804&media=http%3A%2F%2Fwww.minuszerodegrees.net%2Fxtfdc%2FXT-FDC%2520-%2520jumper%2520configuration%2520-%2520DP8473V%2520in%2520socket%2520U2.jpg|{{https://retrobrewcomputers.org/lib/exe/fetch.php?w=300&cache=recache&tok=835cfb&media=http%3A%2F%2Fwww.minuszerodegrees.net%2Fxtfdc%2FXT-FDC%2520-%2520jumper%2520configuration%2520-%2520DP8473V%2520in%2520socket%2520U2.jpg?300|www.minuszerodegrees.net_xtfdc_xt-fdc_20-_20jumper_20configuration_20-_20dp8473v_20in_20socket_20u2.jpg}}]]

==== Alternate Controller Chips ====

The primary intent is for a National Semiconductor PC8477B floppy disk drive controller chip to be used in socket U16. There are two other options:

**Intel 82077AA** - in socket U16, an 82077AA is used in place of the PC8477B. Note that the -5 version of the chip (i.e. 82077AA-5) does not support 2.88M drives. **At May 2013, only one tester has the 82077AA working in the XT-FDC. See the 'Known Problems/Issues' section below for more information.** The use of an 82077AA has two unique requirements:

Capacitor C23 in place.

Jumper JP10 on.

**National Semiconductor DP8473V** - nothing in socket U16, and a DP8473V in socket U2

==== Known Problems/Issues ====

**82077AA chip** - May 2013: It was anticpated that an 82077AA chip would work in socket U16. It works in modem7's second-revision prototype board, but not in the second-revision boards of nestor nor Kiwisek. For now, just be aware that there is a risk of the XT-FDC not working if an 82077AA is used.

**360K Drives** - Some 360K drives generate a signal on pin 34. For 360K drives that do, that will be a READY signal. A READY signal will be a problem for the XT-FDC. If you intend to connect a 360K drive to the XT-FDC that generates a signal on pin 34, then disconnect pin 34. Some drives have a jumper that can be removed to achieve that (e.g. the JU-455-7 has an 'RY' jumper). For information, that requirement is not unique to the XT-FDC board. The IBM 5162 and 5170 computers have the same requirement. Note: 1.2M drives will be expected to generate a DISK CHANGED signal on pin 34.

**“ROM” Errors** - the following problem was fixed in version 2.2 of Sergey's BIOS:

On the IBM 5150 (later model), the following errors will be seen on computer power on: F660 ROM, F860 ROM, FA60 ROM, FC60 ROM

On the IBM 5155 and IBM 5160, the following errors will be seen on computer power on: F6600 ROM, F8600 ROM, FA600 ROM, FC600 ROM

===== Builder's Notes/Comments =====

Please use this space to add any notes/comments on this board that don't fit into the above sections. (Periodically, these comments may be re-arranged to be better incorporated into a new revision of the wiki page.) Please sign your comments using the wiki “Insert Signature” feature!

===== Photo Gallery =====

===== File List =====

Filename

Filesize
Last modified
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:28c64.pdf|28c64.pdf]]
660.2 KiB
2016/02/28 13:37
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:am29f040.pdf|am29f040.pdf]]
241.2 KiB
2016/02/28 13:37
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:dp8473.pdf|dp8473.pdf]]
354.4 KiB
2016/02/28 13:37
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:floppy_bios-2.2.bin|floppy_bios-2.2.bin]]
8.0 KiB
2016/02/28 14:23
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:floppy_bios-2.2.tar.gz|floppy_bios-2.2.tar.gz]]
100.4 KiB
2016/02/28 14:23
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:isa_xt-fdc-001.zip|isa_xt-fdc-001.zip]]
128.1 KiB
2016/02/28 13:37
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:pc8477b.pdf|pc8477b.pdf]]
573.6 KiB
2016/02/28 13:37
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:printing_xt-fdc-brd.pdf|printing_xt-fdc-brd.pdf]]
981.6 KiB
2016/02/28 13:37
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:printing_xt-fdc-sch.pdf|printing_xt-fdc-sch.pdf]]
277.1 KiB
2016/02/28 13:37
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:xt-fdc-components.png|xt-fdc-components.png]]
86.2 KiB
2016/02/28 13:39
[[https://retrobrewcomputers.org/lib/exe/fetch.php?media=boards:isa:xt-fdc:xt-fdc.lst|xt-fdc.lst]]
6.9 KiB
2016/02/28 13:37