Product Overview
Mostek MK3870/20 Single-Chip 8-Bit Microcontroller, 40-Pin Plastic DIP, 1983 Date Code
Condition
Unused new old stock, photographed face up on the black conductive foam it has been stored in. The top of the package reads MOSTEK (c) 8303 over MK3870/20, MK14492N, PHILIPPINES, and JF524900, and every line is crisp and fully legible. Both rows of pins are straight, in line, and bright, with no solder, flux, or board residue and no clipped or splayed leads. The plastic body shows no cracks, chips, or scratches through the marking. One piece in stock, and the photo is of that piece.
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Product Overview
The MK3870 was Mostek's single-chip answer to the multi-chip F8 microcomputer set: processor, mask-programmed on-chip ROM, scratchpad RAM, parallel I/O, and a timer folded into one 40-pin plastic DIP at a time when that job usually took a board full of parts. Devices from this family ran appliance controls, automotive modules, arcade and consumer hardware, and industrial timers through the late 1970s and into the 1980s. This one is marked MK3870/20, and the suffix is how the versions in the family are told apart. The third marking line, MK14492N, is the kind of secondary number Mostek used to identify a customer's mask-programmed ROM pattern. We have not read the ROM, so the program inside is not confirmed - verify it against your application before use. The 8303 date code puts assembly in 1983, and the package is marked PHILIPPINES with lot marking JF524900.
Key Features
- Manufacturer: Mostek
- Part number as marked: MK3870/20
- Secondary marking: MK14492N
- Lot marking: JF524900
- Device type: single-chip 8-bit microcontroller
- Package: 40-pin plastic dual inline package (DIP), through hole
- Date code: 8303 (1983)
- Country of assembly as marked: Philippines
- Condition: unused new old stock, markings and pins as photographed
- ROM contents: mask programmed at the factory and not read here - not confirmed, verify before use
- Electrical ratings and pinout: not confirmed - verify against the Mostek data sheet before use
- Quantity available: one piece, the exact unit photographed
Applications
- Arcade and pinball board restorers hunting a period-correct 3870 in the original plastic DIP for a control board that will not take a modern substitute
- Vintage computing collectors assembling an F8-era reference set who want a dated, clearly marked Mostek example rather than a sanded mystery chip
- Service technicians keeping 1980s appliance, automotive, or industrial timer hardware running where the single-chip controller is the whole board's brain
- Engineers and instructors studying mask-ROM microcomputers who want a real device on the bench for a read fixture or a teaching example
Frequently Asked Questions
What program is in the ROM?
Not confirmed. The MK3870 holds its program in mask ROM set at the wafer stage, so this device carries whatever pattern the original customer ordered under the MK14492N number. We have not read or dumped it. Buy it for the marked device, not for a specific firmware.
Has this one been powered up or tested?
No. It is sold as the unused, clearly marked part shown in the photo, with the markings and the pin condition as the visible evidence. Electrical performance is not confirmed - check the Mostek data sheet for pinout and supply requirements before you socket it.
Does the /20 suffix matter if my documentation just says MK3870?
It can. The 3870 was sold in several suffixed versions and the suffix is how you tell them apart. This package is marked MK3870/20 and that is the only version claim we make. If your board notes call out a different suffix, compare the two against the data sheet before ordering.
Why buy this one photographed chip instead of chasing a surplus lot or an auction pallet of 3870s?
Because this is a stock of one, and the whole of what you are buying is already on the table. With a mask-ROM device the markings carry most of the information, and all five lines on this chip are legible in the photo before you spend anything: MK3870/20, MK14492N, the 8303 date code, the Philippines assembly line, and the JF524900 lot. A lot or a pallet of 3870s is usually a mix of suffixes and ROM patterns with a share of desoldered pulls, and the sorting happens after it lands and after you have already paid for the duds. This is not a bin to draw a count from and it is not a stock photo standing in for whatever ships - it is the single piece pictured, unused, with straight bright pins, listed on its own. Shipping is $8 flat rate and free once your order passes $28, and orders leave our Idaho warehouse the same or next business day.
Somewhere in 1983 a customer ordered a ROM pattern, Mostek pressed it into the mask, and this chip has waited in foam ever since without once being asked to run it. If you are keeping an F8-era board alive or building a shelf of single-chip history, the first instruction cycle is yours to start.
