Panasonic JB-3000

Matsushita Electronics is a huge Japanese electronics company who used the brand names National, Panasonic, Sanyo and Technics in the past, and who are currently known as Panasonic. Advertised as the National mybrain3000, but officially the National Panasonic JB-3000**, (branded "Panasonic" only), it consists of the JB-3001 Logic Unit, JB-3038 8" Disk Drive, JB-3062 Display and other units that we don't have.-- "we" being Friend-in-Crime Jannie (who got these from Peter Job) and I who in a moment of weakness volunteered to foster them.

It's an MS-DOS but not PC-compatible* 8088 machine from the time when the 8088 was called the iAPX88/10. The date code on most of the chips is 1982. It started out with 8" disk drives, and you could also run CP/M-86.

There are a few of these machines in the hands of collectors, but they don't have much more than a few pictures online.

However, when Ericsson wanted to get into the computing market they badge-engineered the Step/One -- and Fredrik Öhrström has a lot of documentation for the Step/One available online.

* It will never run Flight Simulator.
** According to Fredrik Öhrström's documentation the mybrain3000 had a different character generator ROM, so maybe it was only the mybrain in the very early stages? Or (since the mybrain character generator contains Kanji where the JB-3001 contains graphics elements) Japan vs rest-of-world?

8" vs 5 1/4"

8" drives use 1024 byte sectors, which means MSDOS for such a system is... strange. Basically, IO.SYS differs from the IO.SYS for 5 1/4" drives (while MSDOS.SYS is the same) -- this means you can't mix 8" and 5 1/4" drives in one system, you have one or the other and that's it.

Of course this makes transferring software to an 8" system challenging.


The display controller is a Hitachi HD46505, a.k.a. Motorola MC6845, as used in Which does not give me a clue as to the modes available on this machine. Some of the above, maybe all of the above, who knows.


There are sockets for eight x 2764 (8k byte) EPROMs, two (#6, label "PROM-60" and #7, label "PROM-73") are fitted.

ROM #6 looks like it might be a character generator, but does include the string "The Panasonic Personal Computer". ROM #7 contains the string "ROM BIOS version 2.07 9-11-1982".

Each ROM socket has two jumpers, marked "P" (for 8K EPROM) and "M" (for 8K Mask ROM).

Rom disassembly

Using 8086tiny and debug, here's what I have so far.


Standard RAM is two banks of 8 (no parity) x 4164 for 128k. A daughtercard holds another 128k.


The keyboard controller looks similar to the standard PC keyboard but it's not the same. Comms is uni-directional, both signal lines (assuming a clock and a data for now) are outputs from the 7416 hex buffer.

Also, the 8748 (with Mitsubishi Electric sticker) should have enough pins to scan the matrix, why add a 74159? Early days. Keyboard 8748 dump, disassembly.

The connection between the main unit and the keyboard consists of +5V and GND, as well as two uni-directional signal lines. But the PCB has a five-pin connector. And the connector on the JB-3001 side is a DIN-6 (presumably because the one video connector is a DIN-5).

The 8" floppy drives

The drives are very nice JA-751 units, with a door lock solenoid and a head load solenoid and specifications on Bitsavers.

The JA-751 does seem to need the TG43 signal.

	                Drive   PC
 2 Low Current (TG43)       <-- Lower write current when low
 4 Motor On            -->
 6 MFM Mode                 <-- 1 = FM, 0 = MFM
 8 VFO D               -->
10 Double-Sided        --> Media is double-sided
12 Disk Change         --> When disk has changed, until Ready again
14 Side Select              <-- High for side 0 Low for side 1
16 In Use                   <-- Turn LED on
18 Head Load                <-- Low to load the head, lock the door, light the LED
20 Index               --> Once per rev
22 Ready               --> 0 when Disk in and up to speed
24 VFO Sync                 <-- 0 allows read
26 DS1                      <-- Select which drive
28 DS2                      <--
30 DS3                      <--
32 DS4                      <--
34 DIR                      <-- Low = in
36 Step                     <-- Step on trailing edge
38 Write Data               <-- Data to write
40 Write Gate               <-- Low enable write
42 T00                 --> 0 on track 0
44 Write Protect       --> 0 if write protected
46 Raw Data            --> 
48 Rd Data             --> From VFO
50 Window              --> From VFO	


The floppy controller is on a separate PCB, and uses a Fujitsu MB8876A (basically a WD1791) FDC.

From MAME myb3k_fdc.cpp:

    FDC4710 - 5.25" FDD4730
     - 1-2 x SSDD 40 tracks, 8 sectors/track, 512 bytes/sector 160KB

    FDC4711 - 5.25" FDD4731/FDD4732 (FDD4732 has external power needed for drive 3-4)
     - 1-4 x DSDD 80 tracks, 8 sectors/track, 512 bytes/sector 720KB

    FDC4712 - 8" FDD4733
     - 1-4 x DSDD 154 tracks, 8 sector/track, 1024 bytes/sector 1232KB

This page last modified 2024-01-14