Boxed MOS 6502 CPU

Back in 1975, you could order a boxed 6502 CPU directly from MOS in Norristown, PA. Here are some high-res photos of such a box and its contents.

This is the box the 6502 and its documentation was shipped in. It measures 30cm × 25cm × 4.5 cm.

On the top, there is an 8.5″ × 5.5″ sticker saying

MOS MICROCOMPUTERS
MOS TECHNOLOGY, INC.
VALLEY FORGE CORPORATE CENTER • 950 RITTENHOUSE ROAD • NORRISTOWN, PA. 19401

The open box reveals documentation at the bottom, and the chip at the top right. There is a spot for another chip at the top left that is empty.

The height of the box is just perfect for the two books.

The two books, the “Hardware Manual” and the “Programming Manual” are 178 and 254 pages, respectively.

The “MCS6500 MICROCOMPUTER FAMILY HARDWARE MANUAL” (Publication Number 6500-10) from August 1975 is available from archive.org. It came with a one-page erratum about the set-overflow pin only being available on the 6502, not the 6501.

These manuals were printed at a time where MOS was offering two 6500-family CPUs: The 6501, which was pin-compatible with the Motorola 6800, and the 6502 with an on-chip clock oscillator. After a lawsuit with Motorola, the 6501 was dropped in March 1976.

The “MCS6500 MICROCOMPUTER FAMILY PROGRAMMING MANUAL” (Publication Number 6500-50) from August 1975 doesn’t seem to be archived anywhere, but the January 1976 version (6500-50A) is available at 6502.org, and the Synertek version is identical except for the title page. This version does document the “ROR” instruction, which did not work correctly in the first mask revision.

The 6502 CPU is in a plasic tray in the cardboard.

The CPU is the ceramic “MCS” version.

The markings say “MOS MCS 6502”, and the date code is 4175, which is week 41 of 1975. This chip has the original mask with the ROR bug. The only computers this would work correctly in are the Apple I and the KIM-11.

At the bottom, it says “19-155”, and there is a black dot.

The invoice came in this custom envelope with the MOS address and logo printed on. It also carries a MOS stamp next to the Norristown postal stamp dated October 31, 1975.

The invoice is number 2194 and dated October 29, 1975. It seems MOS invoices came pre-printed with the five products MOS was selling:

  • MCS 6501 (20.00 USD)
  • MCS 6502 (25.00 USD)
  • Hardware Manual (5.00 USD)
  • Programming Manual (5.00 USD)
  • Cross Assembler Manual (4.00 USD)

As this was before March 1976, the 6501 was still available.

This invoice is about one 6502 and the hardware and programming manuals, and totals to 35 USD.

The 48 page “MCS6500 MICROCOMPUTER FAMILY CROSS ASSEMBLER MANUAL” was not part of this order, but it is available from retro.hansotten.nl2.

Inside the box, there was a packing list: a carbon copy of the invoice.


  1. All Apple I computers and some KIM-1 boards shipped with the original 6502, so all software had to work around the faulty ROR instruction.

  2. The cross-assembler ran on the “G.E. Timesharing” system and on the “NCSS system”. This is the assembler that defined the syntax of all Commodore 8 bit source code: .PAGE, .SKIP, etc.

3 thoughts on “Boxed MOS 6502 CPU”

  1. I find it interesting that the cross assembler even allowed comments after the opcode without separating semicolon, just with space as separator!

  2. I thought the blueprints as preserved by Donald Hanson showed that the 6501 and 6502 were single-mask variants, not bond-out options?
    See [650X Schematic Notes – VisualChips – Visual 6502]

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