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S > SANYO  > MBC-55x   


Sanyo
MBC-55x

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 (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.

_________________

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

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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.

          
Tuesday 2nd April 2002
philip yanov (Greenville, SC)

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.

          
Sunday 26th July 2009
Adam Marchaud (Ohio, USA)

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.

          
Monday 25th August 2008
Steven Koehler

 

NAME  MBC-55x
MANUFACTURER  Sanyo
TYPE  Home Computer
ORIGIN  Japan
YEAR  1982
END OF PRODUCTION  1988
BUILT IN LANGUAGE  Sanyo Basic
KEYBOARD  QWERTY full-stroke keyboard with numeric keypad
CPU  Intel 8088
SPEED  3.58 MHz
CO-PROCESSOR  Optional Intel 8087 math coprocessor
RAM  128 KB or 256 KB depending models, includes 16 KB V-RAM
VRAM  48 KB(includes 16 KB of main RAM)
ROM  8 KB (IPL/CG)
TEXT MODES  40 x 25 / 80 x 25
GRAPHIC MODES  144 x 200 / 576 x 200 / 640 x 400 (or 640 x 200 ?)
COLORS  8
SOUND  Buzzer, can only generate a single buzztone sound (fixed duration)
SIZE / WEIGHT  main unit : 380(W)x112(H)x360(D) mm
keyboard : 442(W)x45(H)x174(D) mm
I/O PORTS  Centronics printer port, RS-232c (optional), RGB (DIN-8) & composite vide outputs, joystick/paddle (optional), keyboard (DIN-5), external ? (optional)
BUILT IN MEDIA  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)
OS  MS-DOS 2.11, optional: CP/M 86 & Concurrent CP/M-86
POWER SUPPLY  Built-in PSU
PERIPHERALS  128 KB RAM expansion
PRICE  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)


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