Sothius' Home of Ancient Microcomputers - Commodore 128D-CR (ASSY 250477)

Commodore 128D-CR

Commodore 128D CR (52 KBytes)

The C128D-CR with its built-in CBM 1571CR and a CBM 1084 monitor. Monitors like the 1084 provided input for the C128's RGBI- and VIDEO-signals (the latter via FBAS), so that you could use both 40- and 80 column modes with only one monitor
(picture copyright by M.A.Grundke)

Specifications

Name Commodore 128D-CR ('cost reduced', see misc)

Codenames 'PC128' or '128PC' (in first announcements and adverts)

Made by Commodore Business Machines (CBM)

Released 1988
the first C128 was introduced on CES 1985 in Las Vegas
the first 128D-version appeared in early 1986

Serial-No. HB1 012840

Board-info
COMMODORE C128DCR PCB ASSY NO. 250477
GX-211 VO 8701 94V-O
FAB. NO.
355116 REV.1 (lower board-side)
GX-211 VO
94V-0 (lower board-side)
also see the board overviews

CPUs MOS 8502R0 (6510 code-compatible, HMOS-2 process)
Zilog Z80B (8080 code-compatible)
additional MOS 6502AD (NMOS) for the integrated 1571CR
according to Bil Herd, the C128's chief hardware designer, the Z80 wasn't planned in early development. But after problems with C64 carts' power consumption (especially with the CP/M cartridge), he decided to simply (?) add it to the machine's board, solving other problems as well (e.g. some C64 carts crashed the C128 at startup, because MMU was initialized in 128-mode. So the Z80 was used to initialize the MMU correctly...) Thus, 'by accident', the C128 became CP/M compatible

Speed
8502 (128-mode): 1.97 MHz (PAL)/ 2.02 MHz (NTSC)
8502 (64-mode): 985.248 KHz (PAL)/ 1.0227 MHz (NTSC)
Z80 (CP/M-mode): 4 MHz

RAM MOS 8722R2 MMU
128 KB RAM:
4 pcs. OKI M41464-15 (64Kx4 SRAM)
RAM is divided into two banks, each 64 KB in size. Bankswitching is provided by the MMU (the 8502's address space is only 64 KB)
64 KB DVDC video-RAM:
2 pcs. OKI M41464-15 (64Kx4 SRAM)

one Samsung KM6816AL-15 (2Kx8 SRAM) used as VIC-II 'color-RAM'
another KM6816AL-15 used as buffer for the built-in 1571CR
expandable to 640 KB (via CBM 1750 RAM-expansion)

ROM/ Native OS
C318022-02 Commodore BASIC V7 (128-mode, 32Kx8)
C318077-01 (32Kx8) containing
Commodore BASIC V2 (64-mode, 8K)
CBM C64 KERNAL Rev. 3 (64-mode, 8K)
CBM 128 KERNAL (128-mode, 8K)
C128 screen-editor (128-mode, 4K)
Z80 BIOS (CP/M-mode, 4K)

C315079-01 ASCII/ DIN character-generator ROM (8Kx8)
C318047-01 (CBM DOS 3.1, 1571CR's firmware, 32Kx8)
there's also an empty function-ROM socket (for 23256-type, 32Kx8 EPROM), allowing the addition of software. Although I've never heard of C128's with additional software, Commodore made use of function ROMs in the PET-series (e.g. some came with 'Execudesk' in ROM, which is a business software), and the Plus/4 (3-plus-1)

C128 modes
128 mode is the native mode at startup. It offers the great BASIC 7.0, a machine language monitor, 40/ 80 column operation, serial burst mode for CBM 1570/ 1571 drives and, of course, 128 KB RAM
64 mode, activated by the command GO 64 in BASIC 7.0:
MMU reconfigures the memory map to that of a C64 (i.e. disable the 2nd memory bank, disable C128 BASIC/ KERNAL and enable C64 BASIC/ KERNAL)
the CPU slows down to C64-speed (/2)

a CBM 1570/ 1571/ 1571CR, if present, enters 1541-mode
CP/M Plus mode is activated at startup, should a CP/M Plus 3.0 system disk be found:
MMU reconfigures the memory map (i.e. disable C128/ C64 ROMs, activate Z80 BIOS)
Z80 CPU takes over, 8502 is disabled
an attached CBM 1570/ 1571 switches to MFM mode
the standard CP/M boot procedure takes place (i.e. load CP/M BIOS, BDOS and system parameters, run console command processor)
according to COMPUTE!'s gazette, issue 24/ 1985, Commodore's CP/M Plus can fully access the C128's capabilities, such as SID sound, VIC graphics and sprites

Keyboard/ Layout 92 keys/ combined DIN and ASCII layout
the german version keyboard contains both ASCII and DIN-characters (i.e. both 'QWERTY' and 'QWERTZ'). To toggle the layout, there is an ASCII/ DIN function key
as mentioned in the video C128 20th "HI,ALL" by Bil Herd and Dave Haynie, the 128-series keyboard layout was inspired by the VT100 terminals, which were very common these days
also see the keyboard closeup

Graphics MOS 8566R3 VIC-IIE ('Video Interface Controller') for 40 col.mode
MOS 8568 DVDC ('Digital Video Display Controller') for 80 col.mode
MOS 8701 clock generator
Maximum resolutions:
640x200/ 640x400 (i) monochrome (16K DVDC-RAM)
736x354/ 736x708 (i) monochrome (64K DVDC-RAM)
all C128D-CR (and the prototype C128-CR) came with 64K DVDC RAM, whereas the older C128/ C128D had only 16K. However, older machines can easily be upgraded by replacing the RAMs
plus all C64 modes of resolution (created by VIC-IIE)
Max.Colors: 16 ('multi-color' @ 160x200 pixels)
Text: 40x25/ 80x25/ 80x30/ 80x50 with graphical characters
VIC-II can create up to 256 movable display objects ('sprites'), 8 per line, and max. 21x24 pixels each
this MOS 8566 is the VIC-IIE's PAL-B version; the NTSC-M version was called 8564, the PAL-N version 8569. The DVDC was not bound to any video standards

Sound MOS 8580R5 SID ('Sound Interface Device')
3 independant voices, each with 9 octave range (0.1Hz-4KHz in 0.059Hz steps)
4 waveforms (sawtooth, triangle, variable pulse & noise)
programmable ADSR (attack, delay, sustain, release) envelope generator
programmable filter, independantly selectable for each voice (low pass, high pass, Band pass, notch outputs)
master volume control

Media MOS 5710 floppy-controller
Motorola MC2871A read/ write amplifier
integrated CBM 1571CR diskdrive
standard Audio-cassettes (via CBM VC-1530 'Datasette')
5.25" disks, 170 KBytes/ disk (GCR-format)
5.25" disks, 336 KBytes/disk ('double density', MFM-format); used for the C128's CP/M mode

all external CBM serial drives like CBM 1541, CBM 1541C, CBM 1541-II, CBM 1570 can be connected
since device 8 is already occupied by the integrated 1571CR, external drives have to be configured to another address
note that CBM 1570 and CBM 1571 diskdrives support the C128's burst mode for serial high-speed communication

other drives via IEE488-interface (like SFD 1001, CBM 2031 etc)
later: 3.5" disks (CBM 1581), 800 KBytes/disk
later: harddisks up to 30 MBytes

Input/ Output 2x MOS 6526A CIA ('Complex Interface Adaptor')
MOS 8721R3 PLA ('Programmable Logic Array')
R65C22P2 CIA (for the integrated 1571CR)
UM6522A VIA ('Versatile Interface Adaptor' for the 1571CR)
MOS 251828-01 PLA (for the 1571CR)
25 pin SUB-D keyboard
2x 9 pin joystick/ mouse/ paddles/ lightpen
44 pin female edge conn. cartridge interface
6 pin DIN CBM serial IEC-bus (printer or up to 5 diskdrives)
12 pin male edge conn. CBM cassetteport
24 pin male edge conn. 'user-port' (8 bit, programmable I/O, e.g. for modems, centronics-adaptors)
multiple video outputs:
8 pin DIN-41524 audio/video (40 column mode)
9 pin SUB-D RGBI-port (80 column mode)
RF TV-out
standard input plug for powercord
the C128D/ C128D-CR have two reset-buttons: one for the machine itself, the other for the integrated 1571CR

Miscellaneous
The C128-series was intended to be the C64's successor, after the 264-series had failed so miserably. And indeed, CBM avoided many mistakes they did with the 264s: the C128 was (almost fully) C64-compatible, came with a comfortable keyboard by default (in Germany even with DIN-layout) and 80 column mode. The C128D, introduced shortly afterwards, was the professional version with detached keyboard and integrated CBM 1571
Two versions of the C128D do exist:
the first, 'plastic case' C128D has an internal fan, only 16 KBytes VDC-RAM and a carrying-handle. The integrated 1571 is a standard drive, so there's an additional board with its controller logic
the second, cost-reduced C128D-CR (like this one) has a stable metal case, neither fan nor handle but 64 KBytes VDC-RAM instead, enabling higher resolutions (which were rarely used, by the way). The integrated drive is a 1571CR, with its controller logic integrated on the C128D-CR's board. The reason for using a metal case is not quite clear, maybe it was due to stricter EM regulations in some countries?

Some interesting C128-prototypes did exist, e.g. a C128D with built-in 3.5" drive and one-button mouse, a C256 (with 256 KB RAM), machines with integrated harddisks and even some standard (flat) C128 with integrated 3.5" drives, looking quite interesting. However, none of these made it into production - not even samples seem to exist... One machine, however, existed in production quality: the C128-CR, which was a 'flat' C128 based on the C128D-CR's cost-reduced board (including 64K DVDC RAM)
The diskdrives CBM 1570 (single-head) and CBM 1571 (dual-head) were created especially for the C128-series and could handle CP/M disks (via MFM-decoding), required for CP/M-mode

GEOS by Berkeley Softworks was also ported to the C128 (and they called it, surprisingly, GEOS128). Supporting the VDC high-resolution mode, RAM expansions and mouse, it brought a professional graphical user-interfaces to the 8-bit desktop

If you want to know who the C128 development team was, try entering SYS 32800,123,45,6 in 128-mode (or see the pic below)

SYS 32800,123,45,6 screenshot (15 KBytes)

The Commodore 128-series' developers, appearing when the undocumented system-call SYS 32800,123,45,6 is invoked. Have a closer look at the Herdware :-)

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Sothius' Home - Museum - Commodore - Commodore 128D-CR - additional pictures

Name	Commodore 128D-CR ('cost reduced', see misc)
Codenames	'PC128' or '128PC' (in first announcements and adverts)
Made by	Commodore Business Machines (CBM)
Released	1988 the first C128 was introduced on CES 1985 in Las Vegas the first 128D-version appeared in early 1986
Serial-No.	HB1 012840
Board-info	COMMODORE C128DCR PCB ASSY NO. 250477 GX-211 VO 8701 94V-O FAB. NO. 355116 REV.1 (lower board-side) GX-211 VO 94V-0 (lower board-side) also see the board overviews
CPUs	MOS 8502R0 (6510 code-compatible, HMOS-2 process) Zilog Z80B (8080 code-compatible) additional MOS 6502AD (NMOS) for the integrated 1571CR according to Bil Herd, the C128's chief hardware designer, the Z80 wasn't planned in early development. But after problems with C64 carts' power consumption (especially with the CP/M cartridge), he decided to simply (?) add it to the machine's board, solving other problems as well (e.g. some C64 carts crashed the C128 at startup, because MMU was initialized in 128-mode. So the Z80 was used to initialize the MMU correctly...) Thus, 'by accident', the C128 became CP/M compatible
Speed	8502 (128-mode): 1.97 MHz (PAL)/ 2.02 MHz (NTSC) 8502 (64-mode): 985.248 KHz (PAL)/ 1.0227 MHz (NTSC) Z80 (CP/M-mode): 4 MHz
RAM	MOS 8722R2 MMU 128 KB RAM: 4 pcs. OKI M41464-15 (64Kx4 SRAM) RAM is divided into two banks, each 64 KB in size. Bankswitching is provided by the MMU (the 8502's address space is only 64 KB) 64 KB DVDC video-RAM: 2 pcs. OKI M41464-15 (64Kx4 SRAM) one Samsung KM6816AL-15 (2Kx8 SRAM) used as VIC-II 'color-RAM' another KM6816AL-15 used as buffer for the built-in 1571CR expandable to 640 KB (via CBM 1750 RAM-expansion)
ROM/ Native OS	C318022-02 Commodore BASIC V7 (128-mode, 32Kx8) C318077-01 (32Kx8) containing Commodore BASIC V2 (64-mode, 8K) CBM C64 KERNAL Rev. 3 (64-mode, 8K) CBM 128 KERNAL (128-mode, 8K) C128 screen-editor (128-mode, 4K) Z80 BIOS (CP/M-mode, 4K) C315079-01 ASCII/ DIN character-generator ROM (8Kx8) C318047-01 (CBM DOS 3.1, 1571CR's firmware, 32Kx8) there's also an empty function-ROM socket (for 23256-type, 32Kx8 EPROM), allowing the addition of software. Although I've never heard of C128's with additional software, Commodore made use of function ROMs in the PET-series (e.g. some came with 'Execudesk' in ROM, which is a business software), and the Plus/4 (3-plus-1)
C128 modes	128 mode is the native mode at startup. It offers the great BASIC 7.0, a machine language monitor, 40/ 80 column operation, serial burst mode for CBM 1570/ 1571 drives and, of course, 128 KB RAM 64 mode, activated by the command GO 64 in BASIC 7.0: MMU reconfigures the memory map to that of a C64 (i.e. disable the 2nd memory bank, disable C128 BASIC/ KERNAL and enable C64 BASIC/ KERNAL) the CPU slows down to C64-speed (/2) a CBM 1570/ 1571/ 1571CR, if present, enters 1541-mode CP/M Plus mode is activated at startup, should a CP/M Plus 3.0 system disk be found: MMU reconfigures the memory map (i.e. disable C128/ C64 ROMs, activate Z80 BIOS) Z80 CPU takes over, 8502 is disabled an attached CBM 1570/ 1571 switches to MFM mode the standard CP/M boot procedure takes place (i.e. load CP/M BIOS, BDOS and system parameters, run console command processor) according to COMPUTE!'s gazette, issue 24/ 1985, Commodore's CP/M Plus can fully access the C128's capabilities, such as SID sound, VIC graphics and sprites
Keyboard/ Layout	92 keys/ combined DIN and ASCII layout the german version keyboard contains both ASCII and DIN-characters (i.e. both 'QWERTY' and 'QWERTZ'). To toggle the layout, there is an ASCII/ DIN function key as mentioned in the video C128 20th "HI,ALL" by Bil Herd and Dave Haynie, the 128-series keyboard layout was inspired by the VT100 terminals, which were very common these days also see the keyboard closeup
Graphics	MOS 8566R3 VIC-IIE ('Video Interface Controller') for 40 col.mode MOS 8568 DVDC ('Digital Video Display Controller') for 80 col.mode MOS 8701 clock generator Maximum resolutions: 640x200/ 640x400 (i) monochrome (16K DVDC-RAM) 736x354/ 736x708 (i) monochrome (64K DVDC-RAM) all C128D-CR (and the prototype C128-CR) came with 64K DVDC RAM, whereas the older C128/ C128D had only 16K. However, older machines can easily be upgraded by replacing the RAMs plus all C64 modes of resolution (created by VIC-IIE) Max.Colors: 16 ('multi-color' @ 160x200 pixels) Text: 40x25/ 80x25/ 80x30/ 80x50 with graphical characters VIC-II can create up to 256 movable display objects ('sprites'), 8 per line, and max. 21x24 pixels each this MOS 8566 is the VIC-IIE's PAL-B version; the NTSC-M version was called 8564, the PAL-N version 8569. The DVDC was not bound to any video standards
Sound	MOS 8580R5 SID ('Sound Interface Device') 3 independant voices, each with 9 octave range (0.1Hz-4KHz in 0.059Hz steps) 4 waveforms (sawtooth, triangle, variable pulse & noise) programmable ADSR (attack, delay, sustain, release) envelope generator programmable filter, independantly selectable for each voice (low pass, high pass, Band pass, notch outputs) master volume control
Media	MOS 5710 floppy-controller Motorola MC2871A read/ write amplifier integrated CBM 1571CR diskdrive standard Audio-cassettes (via CBM VC-1530 'Datasette') 5.25" disks, 170 KBytes/ disk (GCR-format) 5.25" disks, 336 KBytes/disk ('double density', MFM-format); used for the C128's CP/M mode all external CBM serial drives like CBM 1541, CBM 1541C, CBM 1541-II, CBM 1570 can be connected since device 8 is already occupied by the integrated 1571CR, external drives have to be configured to another address note that CBM 1570 and CBM 1571 diskdrives support the C128's burst mode for serial high-speed communication other drives via IEE488-interface (like SFD 1001, CBM 2031 etc) later: 3.5" disks (CBM 1581), 800 KBytes/disk later: harddisks up to 30 MBytes
Input/ Output	2x MOS 6526A CIA ('Complex Interface Adaptor') MOS 8721R3 PLA ('Programmable Logic Array') R65C22P2 CIA (for the integrated 1571CR) UM6522A VIA ('Versatile Interface Adaptor' for the 1571CR) MOS 251828-01 PLA (for the 1571CR) 25 pin SUB-D keyboard 2x 9 pin joystick/ mouse/ paddles/ lightpen 44 pin female edge conn. cartridge interface 6 pin DIN CBM serial IEC-bus (printer or up to 5 diskdrives) 12 pin male edge conn. CBM cassetteport 24 pin male edge conn. 'user-port' (8 bit, programmable I/O, e.g. for modems, centronics-adaptors) multiple video outputs: 8 pin DIN-41524 audio/video (40 column mode) 9 pin SUB-D RGBI-port (80 column mode) RF TV-out standard input plug for powercord the C128D/ C128D-CR have two reset-buttons: one for the machine itself, the other for the integrated 1571CR
Miscellaneous	The C128-series was intended to be the C64's successor, after the 264-series had failed so miserably. And indeed, CBM avoided many mistakes they did with the 264s: the C128 was (almost fully) C64-compatible, came with a comfortable keyboard by default (in Germany even with DIN-layout) and 80 column mode. The C128D, introduced shortly afterwards, was the professional version with detached keyboard and integrated CBM 1571 Two versions of the C128D do exist: the first, 'plastic case' C128D has an internal fan, only 16 KBytes VDC-RAM and a carrying-handle. The integrated 1571 is a standard drive, so there's an additional board with its controller logic the second, cost-reduced C128D-CR (like this one) has a stable metal case, neither fan nor handle but 64 KBytes VDC-RAM instead, enabling higher resolutions (which were rarely used, by the way). The integrated drive is a 1571CR, with its controller logic integrated on the C128D-CR's board. The reason for using a metal case is not quite clear, maybe it was due to stricter EM regulations in some countries? Some interesting C128-prototypes did exist, e.g. a C128D with built-in 3.5" drive and one-button mouse, a C256 (with 256 KB RAM), machines with integrated harddisks and even some standard (flat) C128 with integrated 3.5" drives, looking quite interesting. However, none of these made it into production - not even samples seem to exist... One machine, however, existed in production quality: the C128-CR, which was a 'flat' C128 based on the C128D-CR's cost-reduced board (including 64K DVDC RAM) The diskdrives CBM 1570 (single-head) and CBM 1571 (dual-head) were created especially for the C128-series and could handle CP/M disks (via MFM-decoding), required for CP/M-mode GEOS by Berkeley Softworks was also ported to the C128 (and they called it, surprisingly, GEOS128). Supporting the VDC high-resolution mode, RAM expansions and mouse, it brought a professional graphical user-interfaces to the 8-bit desktop If you want to know who the C128 development team was, try entering SYS 32800,123,45,6 in 128-mode (or see the pic below)