Why a Commodore 1526 can't print graphics—and the community ROM swap that fixes it

A workshop story about a 1980s firmware gap and the open-source preservation work that closed it.

The Commodore 1526 and MPS-802 dot-matrix printers shipped in 1985 without graphics-printing support in firmware—a quirk that left a whole generation of Commodore home computer software unable to drive them for image output. A community-preserved 1980s German firmware upgrade called Grafik ROM II fixes that, adding the specific commands era-typical software (The Print Shop and similar) emits when it asks the printer for graphics.

I sell this chip at chicagolandretrotech.com, pre-programmed and bench-tested. But the post isn't a product pitch. The chip is the natural artifact at the end of the story; the story itself—1980s commercial firmware, German technical documentation, an open-source dump by a Lemon64 contributor in 2011, and a community archive that's been quietly disappearing from the web—is the part worth reading.

The Commodore 1526 (and its MPS-802 sibling)

The Commodore 1526 is a 1985-era 9-needle dot-matrix printer—a workhorse of the Commodore 64 / Commodore 128 era, sold for word processing, listings, and basic text output. The MPS-802 is the same printer under a different badge: Commodore sold what was internally one product as the MPS-802 in some markets and as the 1526 in others, and the C64-Wiki page for the MPS-802 confirms the two are "identical except for the labels on the front and back." Anything below applies to both equally.

It's a serial-bus printer (the same 6-pin IEC connector that hangs disk drives off a C64), runs on a 6504 CPU, and prints in two modes its stock firmware supports natively: standard ASCII text and the Commodore-specific character set that PETSCII software emits. What it doesn't do out of the box is bitmap graphics—the kind era-typical software like The Print Shop, Newsroom, and various Commodore paint programs emit when they want to print an actual image.

At a glance

What the original ROM couldn't do

The printer hardware is mechanically capable of bitmap graphics. It's a 9-needle dot-matrix printer, after all, not far from the contemporary Epson units that drove the early-PC graphics-printing market. What the printer lacks is a firmware command set that translates host-side graphics requests into print-head actions.

Software like The Print Shop (Brøderbund, 1984) emits Epson-compatible graphics commands when asked to print a banner, sign, or calendar—a stream that says, in effect, "fire pin 1 here, pin 4 there, advance the paper this much." The stock MPS-802 / 1526 firmware doesn't speak that language. The chip looks at the incoming stream, doesn't recognize the graphics opcodes, and either ignores them or—worse—prints them as garbage text.

The fix isn't a hardware modification (the print head is fine). It's a firmware swap. Replace the ROM with one that understands the graphics command set, and the printer suddenly does what the software has been asking for all along.

The fix: marcelv's preservation of Grafik ROM II

Sometime in the late 1980s, a German vendor produced a commercial firmware upgrade called Grafik ROM II for the MPS-802 / 1526. The vendor's identity has been lost to time—Commodore's late-era European market had a vibrant accessories ecosystem, and many small firmware shops produced ROM upgrades that came packaged with a paper manual and a chip. Grafik ROM II was one of these. It adds support for 19 MPS-801 emulation commands plus 3 ESC/P commands for graphic printing, which is exactly what Print Shop and similar era-typical software emits. The original ROM authors get the credit for the firmware itself.

The reason this firmware exists in 2026 is the preservation work of Lemon64 user marcelv. In June 2011, marcelv posted in the Lemon64 forum that he had an MPS-802 with the Grafik ROM II already installed. Using an EPROM programmer, he dumped the ROM to a binary file. He translated the install procedure from the German paper manual into English and posted both. The community then preserved his dump—first at cbm8bit.com, later at pokefinder.org and other Commodore archives as hosts shifted around—but the file has gotten harder to find over time. A 2023 thread on Lemon64 has a user named Wizk83 asking where to locate the ROM because the original cbm8bit.com host had gone down and he couldn't track the file down through normal channels.

marcelv didn't write the firmware; the unknown German vendor did. What marcelv did is the work that keeps obscure 1980s firmware alive in 2026: dump it, document it, share it. That preservation is the reason this chip exists today.

How the upgrade works

The Grafik ROM II is an 8 KB firmware image that lives on a 2764-type EPROM (the M2764A is the standard part used today—same chip family, current-production speed grades). It replaces the original ROM at position U8 on the MPS-802 / 1526 main PCB, next to the 6504 CPU.

The complication—why this isn't a drop-in swap—is that the original ROM and the replacement EPROM aren't directly pin-compatible. Commodore designed the PCB to accept either chip type and provided four jumpers (J1, J2, J3, J4) that reconfigure the socket's connections depending on which chip is installed. The factory configuration matches whatever Commodore originally shipped in U8. For the M2764A EPROM, the jumpers need to be: J3 and J4 closed, J1 and J2 open.

The full install procedure, transcribed from marcelv's post:

1. Open the printer (4 screws on the bottom), remove the print ribbon and knob, lift the upper case.
2. Remove the PCB cover (2 screws).
3. Locate U8, next to the 6504 CPU. Remove the existing ROM. If it's a mask ROM (not an EPROM), the jumpers need changing.
4. Install the new M2764A EPROM at U8.
5. Set jumpers: J3 and J4 closed, J1 and J2 open.

The original ROM is socketed in some units and soldered directly in others. If yours is soldered, you'll need standard through-hole desoldering technique to remove it (and ideally install a socket so future swaps are easier). The jumpers are also small solder-bridge or wire-link points depending on production revision—standard workshop desoldering work.

How I burn and bench-test these

Every chip that ships from the CRT workshop goes through a four-step workflow that combines the binary audit-trail methodology from the Cross-Validation series with a system-level functional test on a real printer.

1. Burn on the EMP-20 with the standard 2 → 1 → 3 → N keystroke sequence: blank check, program with the intelligent algorithm, verify at the 5.00V operating voltage (not the 6.25V programming voltage), then device checksum.
2. Read back the chip into the programmer buffer, save to disk as a .bin file.
3. Binary-compare the readback against marcelv's source file using DOS fc /b. Expected output: No differences.
4. Install and self-test in a real printer. Each chip is labeled with a unique tracking number (small green dot sticker), installed in a working bench MPS-802 with the jumpers set, and run through the printer's built-in self-test. The self-test exercises both the standard character set and the graphics command set the upgrade adds—the Grafik ROM II doing real work on real hardware before the chip leaves the workshop. A section of that actual printout, matched to the chip's tracking number, ships in the same envelope as the chip.

That fourth step is what most chip resellers don't do. It's what catches the corner case the fc /b audit trail can't: bit-perfect data that still doesn't behave on real hardware for some reason—a marginal cell that passes verify and fails at operating temperature, a socket-contact intermittent, a printer-side incompatibility that only shows up under actual print load. The binary compare confirms the bits are right; the printer self-test confirms the bits do what they're supposed to.

Each chip gets a tracking number that matches a printout from its self-test. The buyer gets both.

The printout that ships with your chip is the physical evidence that the specific unit you're installing already printed once on a working MPS-802. If anyone ever questions whether the chip works—including you, six months later—you have the receipt.

Is this upgrade for you?

This upgrade is best for owners of a Commodore 1526 or MPS-802 who want to print graphics from era-typical software and are comfortable with basic through-hole desoldering on vintage hardware. The chip handles the firmware side cleanly; the install is the part that determines fit.

This upgrade is for you if: you own a Commodore 1526 or MPS-802, you want to print graphics from era-typical Commodore software (The Print Shop, Newsroom, paint programs that emit Epson-compatible graphics commands), and you're comfortable with basic through-hole desoldering on 40-year-old hardware.

This upgrade is probably not for you if: the existing U8 ROM in your printer is soldered directly to the board (not socketed) and you've never desoldered through-hole components before. The chip itself drops into a socket—no chip-level soldering required—but the original ROM and the four jumpers require workshop-grade desoldering technique. If you're not sure, find a friend who solders, or look for a local retro-repair shop that handles vintage hardware.

The install is well within reach of anyone who's done basic vintage repair work. It's not within reach for someone whose first soldering job would be this printer. The chips themselves are 40 years old, the boards are 40 years old, and patience matters more than tooling for this kind of work.

Does this work with the new Commodore 64 (the C64 Ultimate)?

The short answer is: yes, in principle, and the new Commodore 64 makes the MPS-802 / 1526 more interesting, not less.

The Commodore 64 Ultimate is the official 2026-era Commodore 64—an FPGA-based recreation built and sold by the company that holds the Commodore brand today. It's not software emulation; it's a gate-level reproduction of the original 6510, the SID, and the rest of the C64 chipset on AMD Xilinx FPGA hardware. The marketing claim is "99.9% compatible with 10,000+ retro games and peripherals," and reviews from early 2026 confirm that Commodore 1571 drives, VIC-1520 plotters, and similar IEC-bus peripherals work cleanly out of the box. Firmware version 1.1.0 (March 2026) added expanded printer support, both real and emulated.

The C64 Ultimate has the same 6-pin IEC serial port that hangs an MPS-802 / 1526 off an original C64. Connect a Grafik ROM II–upgraded printer to a new Commodore 64 and the same software (The Print Shop, Newsroom, paint programs) should drive it the same way it drives a real 1985 C64—because from the IEC bus's perspective, it's the same protocol.

One nuance worth knowing: the C64 Ultimate also ships with a built-in virtual printer that emulates a Commodore MPS-1230 and saves print output as PNG files to a USB drive instead of paper. The virtual printer is the convenient path. It's there for users who want to capture Print Shop output without tracking down 40-year-old continuous-feed paper and a working ribbon cartridge. If you don't want a physical printer at all, the C64 Ultimate covers that case without one.

But if you do want the physical printer—the tactile experience of dot-matrix pins hammering through ribbon onto paper, the sound, the feed-roller noise, the artifacts of 1985-era output—the IEC port is there for that too. And in that case, a Grafik ROM II–equipped MPS-802 or 1526 gives you the most complete version of that experience: real-printer output of the same software that drove a real C64 forty years ago, on the same hardware family, with the firmware that the German vendors of the era intended.

Honest caveat: I haven't personally tested the C64 Ultimate driving an MPS-802 over IEC. The compatibility claim is the manufacturer's, and the IEC protocol hasn't changed since 1983, so the path should work as advertised. If you've actually run this combination, drop me a note—I'd love to add the bench data to this post.

Where to get one

The chip is available at chicagolandretrotech.com: Commodore Printer Graphics EPROM for MPS-802 / 1526. One M2764A EPROM, programmed with marcelv's dump of the Grafik ROM II, full audit-trail and printer-tested before shipping per the workflow above—each chip ships with a section of its actual self-test printout, matched to the chip's tracking number.

If you'd rather burn your own, marcelv's original Lemon64 thread is the place to start: lemon64.com/forum/viewtopic.php?t=36718. The ROM file circulates through the various Commodore community archives (pokefinder.org currently, formerly cbm8bit.com). You'll need an EPROM programmer that handles 2764-series chips—the Cross-Validation series covers most of the modern options.

The reason to buy a pre-programmed chip versus burning your own is the same reason any small piece of retro hardware ships from a workshop instead of from a chip distributor: pre-tested, ready to install, and you have someone to email if it doesn't work in your unit.

Frequently asked

Does this fit my printer? Yes if your printer is a Commodore 1526 or MPS-802. The two are functionally identical units that Commodore sold under different badges. Anything else (the MPS-801, MPS-803, MPS-1230, and so on) is a different product line and not what this ROM targets.

Is this hard to install? The chip itself drops into a socket—no chip-level soldering. The original ROM needs to be desoldered if it's not already socketed, and four jumpers on the board (J1 / J2 / J3 / J4) need to be reconfigured so the socket accommodates the EPROM (J3 and J4 closed, J1 and J2 open). If you're comfortable with basic through-hole desoldering on 40-year-old hardware, this is a 30-minute job. If you've never desoldered before, this isn't the project to learn on—find a friend who solders, or a local retro-repair shop.

Can I burn my own chip from marcelv's dump? Yes. marcelv's original Lemon64 thread documents everything you need: the ROM file circulates through Commodore community archives (pokefinder.org is the current reliable host), and any EPROM programmer that handles 2764-family chips will burn it. The pre-programmed chip from CRT is for people who'd rather skip the burn-and-bench-test step and get a unit that's already been through the audit-trail workflow.

Will this work with the new Commodore 64 Ultimate? In principle yes—the C64 Ultimate has the same 6-pin IEC serial port the MPS-802 / 1526 plugs into, and the IEC protocol hasn't changed since 1983. The manufacturer claims 99.9% peripheral compatibility, and reviews from early 2026 confirm that other Commodore-era peripherals (1571 drives, VIC-1520 plotters) work cleanly. I haven't personally bench-tested this specific combination. If you've run it, ping me and I'll add the data to the post.

A small contribution to the long preservation chain that keeps 1980s Commodore printers running in 2026. The Grafik ROM II was written by an unknown German vendor a generation ago; it survives now because Lemon64 user marcelv dumped, documented, and shared the firmware in 2011. The chip you can buy from me is the same dump on a fresh M2764A, bench-tested at the CRT workshop.

I'm Jeffrey Mays. Bench Notes is where I write up the actual workshop work—burns, builds, repairs, the occasional unreproducible gremlin, and the occasional preservation story. Subscribe to catch the next bench session.