---
title: Sanyo MBC-55x
categories:
- Computers
types:
- Home Computer
origins:
- Japan
years:
- '1982'
cpus:
- Intel 8088
params:
  name: MBC-55x
  image: /media/museum/photos/sanyo_mbc550_1.jpg
  company: /companies/sanyo
  company_name: Sanyo
  specs:
  - label: NAME
    value: MBC-55x
  - label: MANUFACTURER
    value: Sanyo
  - label: TYPE
    value: Home Computer
  - label: ORIGIN
    value: Japan
  - label: YEAR
    value: '1982'
  - label: END OF PRODUCTION
    value: '1988'
  - label: BUILT IN LANGUAGE
    value: Sanyo Basic
  - label: KEYBOARD
    value: QWERTY full-stroke keyboard with numeric keypad
  - label: CPU
    value: Intel 8088
  - label: SPEED
    value: 3.58 MHz
  - label: CO-PROCESSOR
    value: Optional Intel 8087 math coprocessor
  - label: RAM
    value: 128 KB or 256 KB depending models, includes 16 KB V-RAM
  - label: VRAM
    value: 48 KB(includes 16 KB of main RAM)
  - label: ROM
    value: 8 KB (IPL/CG)
  - label: TEXT MODES
    value: 40 x 25 / 80 x 25
  - label: GRAPHIC MODES
    value: 144 x 200 / 576 x 200 / 640 x 200
  - label: COLORS
    value: '8'
  - label: SOUND
    value: Buzzer, can only generate a single buzztone sound (fixed duration)
  - label: SIZE / WEIGHT
    value: |-
      main unit : 380(W)x112(H)x360(D) mm\
      keyboard : 442(W)x45(H)x174(D) mm
  - label: I/O PORTS
    value: Centronics printer port, RS-232c (optional), RGB (DIN-8) & composite vide outputs, joystick/paddle (optional), keyboard (DIN-5), external ? (optional)
  - label: BUILT IN MEDIA
    value: |-
      MBC-550 : 1 x 5''1/4 disk-drive (160k)\
      MBC-555 : 2 x 5''1/4 disk-drive (160k)\
      MBC-555-2 : 2 x 5''1/4 disk-drive (360k)
  - label: OS
    value: 'MS-DOS 2.11, optional: CP/M 86 & Concurrent CP/M-86'
  - label: POWER SUPPLY
    value: Built-in PSU
  - label: PERIPHERALS
    value: 128 KB RAM expansion
  - label: PRICE
    value: |-
      MBC-550: £800 - MBC-555 £1150 (U.K., 1984)\
      MBC-555-2 : 14200 FF (France, january 1986)\
      MBC-55 : 178000 yens (Japan, 83)\
      MBC-555-3 : 16590 FF (France, january 1986)
  tabs:
  - photos
  - adverts
  - links
  photos:
  - title: MONOCHROME VERSION
    subtitle: ''
    text: Like most Sanyo products, the MBC-550 has a perfect manufacturing quality and design. This is also true for the monitor and the peripherals. Sadly, the hardware designers didn't make it a true IBM PC compatible...
    image: /media/museum/photos/sanyo_55x_monoversion_1.jpg
  - title: BACK SIDE
    subtitle: ''
    text: Even the back of the machine has a perfect finish
    image: /media/museum/photos/sanyo_55x_back_1.jpg
  - title: INSIDE THE MBC-550
    subtitle: ''
    text: |-
      **(1)** This plastic housing can receive a second 5''1/4 disk drive or an hard disk.\
      **(2)** NEC 5.25" disk drive (single sided, single density, 160 Kb).\
      **(3)** Socket for the optional Intel 8087 mathematical coprocessor.\
      **(4)** Intel 8088 microprocessor.\
      **(5)** The mother board is originaly fitted with 128 kb RAM, but it's possible to add up to 256 Kb of additional RAM.\
      **(6)** MBC 550 uses a traditional power supply, with a transformer.\
      **(7)** A small loudspeaker for poor sound features.\
      **(8)** The video chip can use, if necessary, almost all the available RAM for graphic display.\
      **(9)** The 8255 interface chipset handle all the peripherals connected to the computer. It was found in every PC compatible systems.\
      **(10)** Parallel Centronics connectors for printers.
    image: /media/museum/photos/sanyo_55x_inside_1.jpg
  adverts:
  - title: MBC-550 FRENCH ADVERT
    subtitle: ''
    text: '''''The personal computer 550, an opened door upon you computing future'''''
    image: /media/museum/pubs/sanyo_mbc550_pub_porte-ouverte.jpg
  - title: FRENCH LEAFLET
    subtitle: ''
    text: Opening to the computers universe.
    image: /media/museum/pubs/sanyo_55x_frenchleaflet_1.jpg
  - title: UK ADVERT (JULY 1984)
    subtitle: ''
    text: ''
    image: /media/museum/pubs/sanyo-mbc55x_pub-uk-1984.jpg
  - title: DUTCH ADVERT (JANUARY 1988)
    subtitle: ''
    text: ''
    image: /media/museum/pubs/sanyo_mbc555_dutch-pub_1988.jpg
  links:
  - title: Sanyo PC Hacker's Special
    url: http://www.qsl.net/k6fv/sanyo.html
    text: dedicated page with interesting information
  - title: Test of the MBC-555 in Dutch
    url: https://archive.org/details/hcc-nieuwsbrief-100/page/38/mode/1up
    text: from HCC Nieuwsbrief-dutch magazine (january 1988)
  - title: Vintage PC pages
    url: http://www.seasip.info/VintagePC/sanyo.html
    text: dedicated page with accurate technical information
  comments:
  - author: philip yanov (Greenville, SC)
    date: Tuesday 2nd April 2002
    text: I used to sell these machines. We wrote software for carpet cleaning companies that ran on them. I think these machines lacked DMA or something. WHat I remember was that every time you accessed the floppy drive, the real time clock stopped and then restarted when access was over. The more you used the floppy drive, the further the real time clock was off. Since it took about a minute to format a floppy for example, the clock would be a minute slow when you were done.
  - author: Adam Marchaud (Ohio, USA)
    date: Sunday 26th July 2009
    text: |-
      I put a lot of time and money into tricking out my old 550. Not only was it fun, but I learned a lot.

      Wordstar as supplied was painfully slow, as it insisted on redrawing the screen completely with every scroll. A patch (which I think came from Soft Sector magazine) told it to use the BIOS screen writing routines, for a huge improvement.

      My 550 also came with a different word processor, Easy Writer, which I tried once and put away.

      The buzzer was not impossible to control, just limited. It was actually a speaker driven by a square wave generated by a programmable UART. Like Robert, I typed in somebody''s BASIC program, again probably from Soft Sector, or maybe from The Silver Box (the Computer Shopper Sanyo 550 column). The program would play something more or less recognizable as music through that speaker. Alas, it took so long to enter even a short piece of music that it wasn''t worth it except to prove it could be done.

      One of the few PC programs which would run as-is was Mark DeSmet''s C compiler. The editor even worked after I relinked the executable, using BIOS routines to replace the direct screen writes. With that compiler and its basic non-macro Intel assembler, I wrote my own modem program with vt220 emulation, chat scripts, and xmodem protocol.

      I wasn''t too interested in the $150-200 Sanyo video board CGA option and instead fitted a $30 Hercules monographics clone. Again using DeSmet''s Intel assembler, I wrote an MSDOS device driver to support it and its printer port, using the Sanyo''s original red and blue video areas in high memory for print spooling buffers. The device driver also added hotkey support so I could use Borland''s Sidekick. With that, I got a surprising number of supposedly incompatible PC programs to run on that machine. Eventually I patched the BIOS on the diskette to talk to the monographics card without the driver.

      I probably still have the source code for most of those drivers and patches, if anyone cares.

      Lots of folks piggybacked memory on the 550s to get 512k or 768k. I used a cleaner method that one of the hardware hackers in our local users'' group figured out. IIRC, we replaced the second 128k of memory with higher density chips for 512k, and tweaked the memory addressing to support the larger chips.

      For a while, I ran two 800K Teac drives using Michtron''s DS-DOS, for a total of 1.6mb online floppy storage.

      Later I fitted a hard disk kit which used a surplus SASI (Shugart''s SASI, not SCSI) controller and a custom board which plugged onto the Sanyo expansion bus and spoke SASI. I eventually put a 40mb Winchester drive on that box. I had to patch the HD kit''s driver for that enormous (!) disc, and replace Sanyo''s feeble linear power supply with a surplus switching supply to provide enough current. (A more common upgrade was fitting larger diodes to Sanyo''s linear supply.) As someone pointed out the Sanyo had no DMA, but since HD transfers were much faster than floppy transfers, at least the HD made PIO a little more tolerable.

      I also added a clock speed doubler, a little "turbo board" which plugged between the CPU and its socket. With a NEC V20 replacing the 8088, that machine could almost hold its own against 8mHz PC clones.

      I kept that little silver box going and useful up until about 1990, when I got my first 80386 machine.

      Lots of great memories. I wish I still had the little guy, but I donated it to Amvets in a cleaning fit one day. I don''t want to know what they did with it.
  - author: Steven Koehler
    date: Monday 25th August 2008
    text: |-
      The floppy drives in these models were from Teac. Interestingly, the drive lights always stayed on when the door was closed. They did not go out even if the drive was not currently being accessed.

      Regarding the video issue: a lot of "IBM PC" software at the time accesed the address of the video cards directly - B800:0000 for color and B000:0000 for monochrome, since the Sanyo had no video card at this address the video output was never seen. I believe Sanyo offered a CGA card that was present at this address for direct memory writing.

      A-OK company wrote a OS for the system as well, called A-OK DOS.

      My MBC-555 would reset by itself if the dishwasher started - I always wondered why, maybe it had to do with the type of power supply.

      The IBM PC/XT at the time had 10 function keys. Notice the Sanyo had half that amount. To get the higher function keys you would need to do these strange shift combinations.
  - author: Mark Raftogianis (USA)
    date: Thursday 16th November 2006
    text: I bought a Sanyo MBC-555-1 iin 1983, primarily due to its low price and color capabilities. It came bundled with WordStar, CalcStar, and DataStar. BASIC was easy to program for graphics. My Sanyo had MSDOS v.1. I bought it from Priority One computers in Los Angeles; they had a big sale at the Los Angeles Convention Center. The Sanyo rep said they were creating an upgrade kit to convert from DOS 1 to DOS 2. Well, that upgrade kit never came. When I talked to Priority One they said they had numerous complaints about Sanyo's support and eventually severed ties with them. After 20 years I still refuse to buy Sanyo products! I eventually bought an IBM close to replace it. I donated the Sanyo to Goodwill.
  - author: Warren Watts (Columbus, OH)
    date: Thursday 30th March 2006
    text: |-
      I purchased an MBC-555-2 via mail order in 1985. I remember spending hours sifting through the Computer Shopper to find the absolute best deal I could.\
      I had an early version of Borland Turbo Pascal that I used on the machine. I remember writing a Pascal version of "Animals" that ran on the Sanyo.\
      During the time I owned the computer, the price of RAM dropped dramatically and I purchased the individual RAM chips necessary to max out the computer's memory. It took quite a few chips as I recall, and I remember painstakingly placing all the RAM on the motherboard.\
      In 1987, I traded it to my boss for an original 128K Apple Mac. He had a small software company, and used the Sanyo for several years afterward to copy and create distribution disks for his products.
  - author: John Domingues (United States)
    date: Friday 7th January 2022
    text: I designed a self refreshing memory board for this computer. Full details were published in Sanyo MB magazine. I still have a copy of this magazine.
  - author: Alain David (Belgium)
    date: Monday 14th December 2020
    text: In 1988 these were still being offered in the Netherlands Sanyo 555/2 2FDD-360DD MS DOS 2.11 256kb RAM BW monitor and Wordstar, Calcstar and Mailmerge incl. 999 Guilders (about 350-400$ or 250-300£ I guess) https://archive.org/details/hcc-nieuwsbrief-100/page/8/mode/1up The same magazine did a reprint of his test of the MBC555 priced at 4995 Guilders (1000$ or 1200£) in 1984 in issue 100 of 1988 https://archive.org/details/hcc-nieuwsbrief-100/page/38/mode/1up
  - author: Alain David (Belgium)
    date: Sunday 29th November 2020
    text: An advert in personal computer world July 1984 states 749£ for the 550 and less than 1000£ (presumably 999£) for the 555. https://archive.org/details/PersonalComputerWorld1984-07/page/153/mode/1up
  - author: Paul Miller (USA)
    date: Sunday 23rd April 2017
    text: |-
      I had an Atari 400 before this by the 550 was my first "real" computer. Like many others here I learned a lot about computers with it. I spent a ton of time on a bulletin board dedicated to the 550 in Michigan (Michigan Software I think?) over a 300 baud modem.

      There was a 550-specific magazine at the time that I poured over every month. Someone published some assembler in there to control the speaker to make tones. I wrote a synthesizer/sequencer (callled Sanyo Synthesizer) using that and had it published in the same magazine, when I was in 7th grade. Someone also published some code to do smooth-scrolling and I used that to make a simple game with a space ship where you fly through some caves, and had that pubished as well.

      The graphics were much better than the standard IBM PC and I wrote a lot of programs with colorful graphics and animation, spending a lot of time working out pictures on graph paper and turning them into bytes.
  - author: willy tarreau (france)
    date: Sunday 2nd August 2015
    text: I used to have an MBC-550 when I was a kid, from 10 to 16 (1984 to 1990). I learned a lot on it. Initially it was shipped with DOS 1.25, which didn''t even support directories. That probably explains why even today there are 4500 files in my home dir! After I accidently destroyed the boot disk, I received a DOS 2.11 floppy as a replacement, and could start to retrieve some MS-DOS 3.20 programs from the school, "crack" them to ignore the wrong DOS version, allowing me to run the wonderful DEBUG utility for the first time. That allowed me to start to write ASM. This machine was provided with a fairly complete manual including the whole schematics. I could write a PC-compatible BIOS that would boot MS-DOS 5.0 and run Tetris. However by then I didn''t understand how to write using the floppy controller (there was no internet to get datasheets), so disk writing was disabled, and tetris scores could not be saved. I could not use Turbo Pascal 3.0 either due to this lack of writing capability.
      For this reason I programmed this BIOS as well as a copy of the original on a 27128 EPROM with a switch on pin A13 so that I could decide what BIOS to boot from. I really had great moments with this machine, and its graphics were quite cool for that time.
  - author: Brian Empey, P.Eng. (Canada)
    date: Wednesday 18th February 2015
    text: |-
      Quirks :: to get the unit below $1000 retail, Sanyo cut a lot of corners. Someone mentioned that it was lacking a DMA controller. That is correct (I have full schematics of the motherboard, and all the original manuals with my MBC-550). In order to read or write from/to the floppy drive, it had to go into a tight SW loop, ignoring all else. Due to the limited memory, WordStar would buffer documents, and swap/load data from the floppy while scrolling or while you entered a lot of text. Users quickly learned that when typing in WordStar, once you heard the loud "Clank" of the disk heads actuating, its time to stop typing, because every character that you type will be lost while its accessing the drive.\
      I created a computer animation for a 4th year arts class at UBC on my MBC-550 with custom code that I wrote in BASIC. The animation was filmed with a borrowed 16mm camera with a single-step mode and a shutter release cable.\
      It was so slow rendering each frame that I had to add a "BEEP" at the end of the rendering to wake me up to capture that frame and hit the space bar to start rendering the next frame.\
      I generated about a 1/2 minute of 24 FPS film, but I recall it taking over 24 hours to do so.\
      Oh, the graphics buffers were very bizarre.\
      The chip''s BIOS was in a unique SANYO windowed EPROM chip that also housed the RED and BLUE video buffers. It only supported 640x200 graphics (16,000 bytes each, so 32k SRAM for RED and BLUE) housed in the same physical chip as the BIOS PROM. It had an RGB output, and a monochrome composite output that only showed the GREEN video. But the GREEN came from the main DRAM memory. So, in theory, you could do monochrome animations by pre-rendering frames into RAM and then re-mapping the video controller for where it should fetch the green pixels. Pretty cool! But I wasn''t ambitious enough to do that.
  - author: Gerry Brophy (canada)
    date: Monday 23rd July 2012
    text: |-
      I have an active Sanyo mbc 550 / 555 computer and I''m creating an archive of software for it.

      http://www.eriscreations.com/sanyo/index.html

      Please let me know if you have any software to contribute so I can add it and of course check it out myself. I have mnay more disks that I am slowly adding to my archive.

      I have a Sanyo mbc 555 w 2 disk drives, colour monitor, joystick, IBM Video Board and a bunch of disks.

      Gerry Brophy\
      gerry@eriscreations.com\
      www.eriscreations.com
  - author: chris (europe)
    date: Monday 5th March 2012
    text: That was my first computer, I was 14 years old, my dad didnnt want a computer for games like commodore 64, it was really awesome, I spent hours to program with Basic
  - author: Jerry Hubbell (Locust Grove, VA, USA)
    date: Friday 21st October 2011
    text: I bought an MBC-555 in February 1984 I believe (when they were first released) and used it to learn programming. I actually developed the program "SolarSim" sold by MichTron and remember how neat it was that they decided to publish it and I still have the SoftSector magazine where the ad for SolarSim was placed. I still have my machine but it hasn''t been booted for over 10 years. If anyone has a copy of SolarSim, I would appreciate hearing from you as I lost my boxed copy I got from MichTron when it was first published.
  - author: Alan W. (USA)
    date: Saturday 3rd September 2011
    text: I have a 555 from my grandpa, who used Calcstar to keep track of stocks. Once in a while, I turn it on. It''s a lot more fun to write BASIC programs on actual hardware, not on some emulator. The computer turns 31 this year, and still runs flawlessly.
  - author: David Siebert
    date: Thursday 1st September 2011
    text: One minor correction, there was no MS-DOS version of Excel. The microsoft spreadsheet was called Multiplan. The store that I worked for carried one but I do not think it ever sold. People wanted PC compatibles and even if your computer was better than the IBM PC no one wanted it. Machines like the Z100 and the Tandy-2000 just sell. The 550 while inexpensive just wasn''t popular at our store.
  - author: Paul Smith (UK)
    date: Saturday 16th April 2011
    text: I ran a user group for the MBC55x back in the late 1980''s from my flat in Bath, UK. It was called "SMUF" for the Sanyo MBC User Forum, and I produced regular disk magazines for a while.... I still have some of them in my lock-up, buried amongst the other aging retro computer gear. I guess it taught me MSDOS and assembler pretty well, and I learned a lot - probably now all forgotten too! Great times....
  - author: Tim Buterbaugh (USA)
    date: Saturday 12th March 2011
    text: |-
      The MBC-550 (or 555) had a design flaw in its serial card. The company I worked for designed a replacement board which we sold to a company named Scottsdale Systems. They sold the improved systems under the name "Sanyo Silver Fox."

      I remember that the test of IBM compatibility in those days was to run "Flight Simulator." I can''t remember if these machines passed that test or not . . .
  - author: James Prew (Albuquerque New Mexico, Usa)
    date: Friday 23rd July 2010
    text: Wow. My First Computer, had the 555 2(360k floppy setup) and used to publish a newsletter with it back in 99. I still have the Dos 1.25 boot disk and WordStar, CalcStar, and ReportStar v3.0 and 4.0 software bundles. It''s amazing that anyone still remembers this.
  - author: Joe Dellea
    date: Monday 25th August 2008
    text: 'Among the quirks to the machine: the power supply was not a regular switching power supply. It was a transformer. Quiet machine. The keyborad lacked the "alt" key. There was a very handy reset button on the left edge of the keyboard. When you push the power button, you definately had the feeling that Sanyo had borrowed some parts from their stereo division!'
  - author: David Botkin (USA)
    date: Monday 25th August 2008
    text: |-
      I owned & used an MBC-555-2 from 1984 until about 1992. It was the first MS-DOS compatible computer that retailed for under US$1000. It was also quite possibly the only (somewhat) IBM-compatible system that was actually SLOWER than an IBM PC (the PC clocked at 4.77 MHz, while the Sanyo clocked at 3.6, giving it a Norton SI rating of 0.8). The 55x motherbaord included a socket for an 8087 math coprocessor, which helped with spreadsheet applications.

      Still, I loved that machine. While the mixed text-and-graphics video made it incompatible with many programs intended for the IBM (Lotus 1-2-3 being the benchmark at the time), WordStar worked just fine, as did Microsoft Excel (the original MS-DOS version) and also Borland's Turbo Pascal compiler. If your consideration was more for file interchangeability (it ran MS-DOS 2.1) than for software compatibility, the Sanyo was a solid, workhorse system at a very reasonable price.
  - author: Richard N. ("Dick") Cote (Mt. Pleasant, SC)
    date: Sunday 23rd December 2007
    text: |-
      Dear Friends: My Sanyo 550, purchased in 1984, was God's gift to a working writer. It came with WordStar, and I wrote seven books using the Sanyo and WordStar version 3.3. It was great fun -- really! -- learning DOS (not optional in 1984!), writing primitive DOS programs, and memorizing all those WordStar commands. My colleague and I, the Rev. George David Exoo, a Unitarian minister and an extraordinary writer, both knew that we would be toast if we didn't know a computer expert when we bought our first computers. And neither of us knew one or how to find one. So we both got identical Sanyo 550s with the same monitor and printer (total price, as I recall: about $1,500 for the package -- so that when something went screwy, we at least had each other to brainstorm with -- and that usually worked. For a writer, back in '84, getting a machine that would remember what you typed, let you change it anytime, and actually print it on paper was like having Christmas every day. And then -- lo and behold -- WordStar learned how to make footnotes that traveled with the text if you moved it! It still makes my heart beat faster when I remember the thrill of seeing THAT!

      Now, 23 years later, I cringe every day knowing that one of my PCs is going to crash, lock up, or refuse to do what it did yesterday. My Sanyo never failed me, and after I gave it to a friend after four years, he used it for two more and then his friend used it another for two more. I'd love to have it back! I'd have it bronzed -- like baby shoes -- and use it as a pedestal to display the books I wrote "way back then." With warmest wishes -- Dick Cote' / dickcote@earthlink.net
  - author: Blake Patterson (Alexandria, VA (USA))
    date: Sunday 24th July 2005
    text: 'Does anyone have a screenshot of the Sanyo version of the game from MichTron called Time Bandit? The Sanyo version took unique advantage of the Sanyo''s higher # of on-screen colors vs. the PC of the day. Thanks.'
  - author: Richard Yien (New York)
    date: Tuesday 3rd August 2004
    text: This was a good little machine... got it around 1983 and used it for WordStar, dBase, and BASIC programming. I remember buying it at Crazy Eddie or some place like it and thinking that it was a great deal for a PC compatible - then being disappointed after discovering that it wasn't really totally compatible. Had it hooked up to a Juki letter-quality printer...
  - author: Omar Egan (El Salvador)
    date: Monday 19th May 2003
    text: We used these machines for our business back in 1985... we later moved to more powerfull PC clones. I still have two of the machines in my attic, and recently cleaned them out only to find, to my amazement, that they still work! Does anyone know if there a users group alive anywhere? It would be great to find people who are still doing usefull things with these machines!
  - author: Robert Lingenfelter (tx)
    date: Wednesday 11th December 2002
    text: I had a 550 and learned alot about computers from it. Subscribed to the mag. I was able to learn some C programing (MIX C compiler), followed an article to get the speaker to play notes instead of that awful "honk!", and even soldered on extra ram chips to expand the memory to a whopping 512K! I kinda still wish I had it to play with. I wonder if anyone got MINIX to run on it?
  - author: Tim Robert (Earth)
    date: Wednesday 10th April 2002
    text: The reset button was near the top of the left side of the keyboard, to the left of the F1 key. When deep in thought about some programming issue, I often found myself idly fingering that button. I had to get out of that habit... My parents inherited my SBC-550 and used it well into the 1990s.
  oc_id: 473
  source:
    url: https://web.archive.org/web/20230417004107/http://www.old-computers.com/museum/computer.asp?c=473
    date: '2023-04-17'
---

The Sanyo MBC-550 was the first of the legitimate "clones" of the IBM Personal Computer. While others (notably the Taiwanese) were duplicating the circuitry and Read-Only Memories (ROMs) of the IBM PC, Sanyo Business Systems designed their own circuitry and wrote their own Basic Input/Output System (BIOS), part of which was in ROM and part was on disk. The character set was also in ROM. In Japan, this computer was the MBC-55. It came with a kanji character set and the CP/M-86 operating system. Sanyo had Microsoft write a special version of their disk operating system (MS-DOS) and command interpreter (COMMAND.COM). They had MicroPro write special versions of WordStar, CalcStar, and EasyWriter which they bundled with the MBC-550, making it a very attractive package, not only for their intended market, business; but also for the computer hobbyist.

The Sanyo 55x was the first MS-DOS compatible computer that retailed for under US$1000. It was also quite possibly the only (somewhat) IBM-compatible system that was actually slower than an [IBM PC](/museum/ibm-pc-model-5150/) (the PC clocked at 4.77 MHz, while the Sanyo clocked at 3.6, giving it a Norton SI rating of 0.8).

It came with 5.25" floppy drives sized from 160 KB to 800 KB. One thing the machine had that was odd was a floppy controller for 4 floppy drives, you simply chained them and adjusted the DSx jumper on the drives. The drives were labeled ABCD and if a hard drive was added it became E even if you only had 2 floppy drives as the BIOS reserved A-D for floppy drives. The floppy drives in these models were from Teac. Interestingly, the drive lights always stayed on when the door was closed. They did not go out even if the drive was not currently being accessed.

They were manufactured & sold from about 1983 to about 1988. The different models are:\
\- MBC-550 : 1 x 5.25" disk-drive (160 KB)\
\- MBC-555 : 2 x 5.25" disk-drive (160 KB)\
\- MBC-555-2 : 2 x 5.25" disk-drive (360 KB)\
\- MBC-555-3 : 2 x 5.25" disk-drive (720 KB)

The default graphics were easy to use: three straight 640x400 bitplanes, R, G, and B. There was no text mode, so stock IBM PC apps that bypassed the video BIOS did not work. The main add-on card was a Sanyo CGA color card, that transformed the original Sanyo into about a 90% PC IBM compatible computer. The CGA board was EXPENSIVE and one version added memory to 640 KB as well.

While the mixed text-and-graphics video made it incompatible with many programs intended for the IBM (Lotus 1-2-3 being the benchmark at the time), WordStar worked just fine, as did Microsoft Excel (the original MS-DOS version) and also Borland's Turbo Pascal compiler. If your consideration was more for file interchangeability (it ran MS-DOS 2.1) than for software compatibility, the Sanyo was a solid, workhorse system at a very reasonable price.

A lot of "IBM PC" software at the time accessed the address of the video cards directly - B800:0000 for color and B000:0000 for monochrome, since the Sanyo had no video card at this address the video output was never seen. Sanyo offered the CGA card that was present at this address for direct memory writing.

There was a pinout on the motherboard for a ribbon cable that would accept a 5 MB hard disk. The 55x motherbaord also included a socket for an 8087 math coprocessor, which helped with spreadsheet applications.

Soft Sector magazine and all the BBS systems specific such as First Sanyo Opus and the Sanyo supporting clubs kept these working and many many mods from power supply fixes to memory addons (768 KB was possible) to serial board mods, hard drive addons, etc came out of these.

The MS-DOS had to be specific to this machine as well, you couldnt boot the generic versions. There were a few aftermarket DOS's that gave extra abilities to include 800 KB from 720 KB floppy drives. A few people even professed to adding 3.5" drives. A-OK company wrote a OS for the system as well, called A-OK DOS.

Among the quirks to the machine: the power supply was not a regular switching power supply. It was a transformer. Also the keyboard had no ALT key - made it nuts to operate software made for IBM specific machines! The IBM PC/XT at the time had 10 function keys while the Sanyo had half that amount. To get the higher function keys you would need to do these strange shift combinations.

When you push the power button, you definately had the feeling that Sanyo had borrowed some parts from their stereo division!

This systems was also proposed when you got a course through NRI.

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**Contributors:** Russ Blakeman, David Botkin, Joe Dellea, Steven Koehler, Victor Frank