Turbo-10 (FC-4012) IBM XT Clone Motherboard
This Turbo-10 IBM XT clone motherboard was part of my first homebrew PC build back in the ’80s. I sourced the case and components from various electronics suppliers—this was well before the days of next-day shipping—so the build came together gradually over about a month. I paired it with a 5¼” floppy drive, powered it up, and to my amazement… it worked!
At the time, it felt like a major achievement. I remember being both impressed and a little let down when comparing it to my Commodore 64: productivity was far superior on the XT, but games just didn’t have the same magic. Initially, I ran it with a monochrome monitor and the classic PC internal speaker, which made the whole experience very “business-like.”
Main Chips:
- NEC D70108C-1 – V20 CPU: 16-bit high-performance CMOS microprocessor, pin-compatible with the Intel 8088 but faster and with some enhanced instructions.
- Intel D8253C-2 – Programmable Interval Timer
- Intel D8259AC-2 – Programmable Interrupt Controller
- Intel D8237AC-5 – Programmable DMA Controller
- PAL-71 – Handles address generation and bus cycle control
- Sockets – One for an optional 8087 math coprocessor, and another for a 2764 EPROM (currently populated) and a socket for a 27256 EPROM unpopulated.
There’s also a single surface-mount IC, curiously the only SMT component on the board. I haven’t been able to identify it yet.
Memory Configuration:
This board has a somewhat unusual memory setup, and I can’t recall exactly how it was mapped. It appears to have 128 KB of RAM with parity support, though the total raw chip capacity is higher. Judging by the 1990 date codes on the chips, I likely upgraded the memory at some point after the initial build.
- 1 × V53C104P – 256K x 4-bit Fast Page Mode CMOS DRAM
- 5 × HY51C100LS – 256K x 4-bit CMOS DRAM
The RAM layout is non-standard for an 8-bit system, so if anyone has insight into how this configuration was intended to work, I’d love to know more.
All the support logic chips on the board are standard TTL.
Final Thoughts:
The NEC V20 was a later upgrade I made—it’s fully pin-compatible with the Intel 8088, but with improved speed and extra instructions. At least I’m fairly certain the original CPU was swapped out for the V20 at some point.
As much as I’d love to power this board up again, I no longer have the manual, and the connectors and jumpers are unmarked, leaving their individual functions a guessing game. My online searches haven’t turned up any documentation so far.
The only markings I can find are:
- Board Part Number: FC-4012
- Sticker 1: “Turbo-10” with a “WJ” or “JW” logo
- Sticker 2: “80 DATA” and the phrase “We Develope [SIC codes] Technology”
If anyone out there has information, a manual, or even just memories of this board, I’d be very grateful for any clarifications or corrections!
