ACC Microelectronics KT-204
| Bus type | ISA |
|---|---|
| Bus width | 8-bit |
| Bus speed | 8 MHz |
| Manufacturer | ACC Microelectronics |
| Chipset | MCS3201FN |
| Compatible with | PC Floppy |
| Connectors | None |
| Requires -5VDC? | No |
| Requires -12VDC? | Yes |
| Config method | Jumpers |
| Floppy Controller | |
| Floppy buses | 2 |
| Drives per bus | 2 |
| Secondary? | Yes |
| ROM type | 28-pin JEDEC |
| Driver | N/A |
The KT-204 is an 8-bit floppy controller capable of supporting up to four 1.44MB drives. It includes a boot ROM, allowing the system to boot from a floppy disk even when the BIOS does not support doing so (e.g. booting from 1.44MB disks on an XT.)
Jumpers
| Drive/size | SW1 | |
|---|---|---|
| Drive 0 | 1 | 2 |
| Drive 1 | 3 | 4 |
| Drive 2 | 5 | 6 |
| Drive 3 | 7 | 8 |
| 360 K | on | on |
| 720 K | on | off |
| 1.2 M | off | on |
| 1.44 M | off | off |
| J1 | Purpose |
|---|---|
| open | Primary FDC controller (base I/O at 0x3F0) |
| closed | Secondary FDC controller (base I/O at 0x370) |
The boot ROM is always at segment CA00 regardless of the jumper setting.
Internal connectors
- CN1
- First floppy bus (drives 0 and 1)
- CN2
- Second floppy bus (drives 2 and 3)
Additional photos
Underside
Jumper settings
BIOS
During POST, a banner similar to the following is displayed:
ACC Microelectronics Advanced FDC Firmware v1.0c
The ROM appears at CA00:0000 to CA00:07FF regardless of the J1 setting.
The card's BIOS only appears to support the controller at the primary address (0x3F0). When set to the secondary address (0x370) the POST freezes unless there is another primary floppy controller present. Booting off the secondary controller does not seem to be possible. This was tested with BIOS v1.0c on a card with no physical jumper installed at J1, so it is possible this BIOS had secondary support removed.
Notes
The card seems to run floppy drives slightly slower than others (possibly due to the custom BIOS.) It also struggles reading some marginal floppies that other newer cards appear to be able to read without problem, using the same physical drive.
Related links
- retroarchive.org ROMs - acc-105b.rom (ACC Microelectronics FDC ROM v105B) is a ROM for this card. The signature at the end of the file states v1.0b so it is unclear where the "5" comes from.
