B500 & B500/B256
As mentioned on the page for the B128,
the CBM-II models were Commodore's last effort to
capture the business market with it's superior proprietary technology.
All the machines in this line are distinguished by the MOS 6509 processor,
Commodore BASIC 4.0 (like that found in the later
CBM/PET computers, the Commodore "SID" sound chip, IEEE-488 peripheral
compatibility, an RS232-C port, and 80 column text video capability. Shown here on the
right is the 128k B500 computer, considered a prototype CBM-II model in the U.S.
These machines are part of the "low profile" CBM-II series, called such because
they feature a single integrated unit with a full business keyboard,
numeric keypad, and 12 function keys.
The B256 is the 256K version of the B128/B500. Whereas the B128 only utilizes
the 64K in bank 1 for BASIC code, and bank 2 for variables, the B256 adds
banks 3 and 4 for variable storage as well. Seen here is a factory produced
B256 (256k) motherboard in a case whose sticker proclaims it as a B500 model
machine. Whether any machines were actually released with a "B256" model
number, or if all B256's are actually B500 model machines with 256k is
unknown. This issue is further confused by the fact that the box this
unit came in proclaims it to be a B256 proper, with no mention of "B500".
Statistics, features, and CBM B500/B256 resources:
Expandable to 256k internal, 704k external
B500 line Kernal
CBM Basic 4.0
MOS Technology 6545 CRTC
9" Monochrome display
80 columns, 25 rows.
MOS 6581 SID
3 voice stereo synthesizer/digital sound capabilities
Male edge-connector IEEE-488 port
Male edge-connector CBM Datasette port
Female RS232 port
Round DIN CBM Monitor port
Female edge-connector CBM-II/PET-II expansion port
1 RCA audio port
Power and reset switches
Full-sized 102 key QWERTY
19 key numeric keypad!
4 direction cursor-pad
Personal Note:The CBM-II line are personally very cool
to me. I used to sit and write little BASIC programs on these things, but they
fell out of favor as my collection grew, so now they are all boxed up. The B500s
both came from eBay