US and German variants of Model B
A special version of the BBC Model B was produced for export to the USA, and to Germany. These models had a redesigned mainboard, internal shielding to reduce electromagnetic interference, and all options (Econet, 8271 disk interface, speech) fitted as standard.
The US model had modifications to its display circuitry, to suit the 60Hz refresh rate used by NTSC televisions. The German model had a translated version of MOS.
Some US Model Bs were left unsold, and were converted back to a UK specification and sold at a reduced price. These are functionlaly equivalent to a UK Model B, but the numbering of ICs and selection jumpers does not correspond to those listed in service documentation.
IC Numbers
| UK Model | Description | US / German |
|---|---|---|
| IC01 | 6502 Processor | ??? |
| IC02 | 6845 / 46505 CRT Controller | IC34 |
| IC03 | 6522 System VIA | IC11 |
| IC04 | 6850 ACIA | ??? |
| IC05 | SAA5050 Teletext Generator | IC82 |
| IC06 | 5C094 Video ULA | ??? |
| IC07 | 2c199 Serial ULA | IC92 |
| IC08 | 81LS95 Hi-res row address buffer | IC27-31? |
| IC09 | 81LS95 Hi-res column address buffer | IC27-31? |
| IC10 | 81LS95 Teletext row address buffer | IC27-31? |
| IC11 | 81LS95 Teletext column address buffer | IC27-31? |
| IC12 | 81LS95 CPU row address buffer | IC27-31? |
| IC13 | 81LS95 CPU column address buffer | IC27-31? |
| IC14 | 74LS245 data bus transciever | IC80 |
| IC15 | 74LS273 Teletext chip buffer | IC81 |
| IC16 | LM555 timer | ??? |
| IC17 | LM324 op-amp | IC24 |
| IC18 | 76489 sound chip | IC23 |
| IC19 | LM386 amplifier | IC25 |
| IC20 | 74LS139 decoder | ??? |
| IC21 | 74LS00 quad 2-input NAND | ??? |
| IC22 | 74LS30 8-input NAND | ??? |
| IC23 | 74LS30 8-input NAND | ??? |
| IC24 | 74LS138 decoder | ??? |
| IC25 | 74LS20 dual 4-input NAND | ??? |
| IC26 | 74LS139 decoder | ??? |
| IC27 | 7438 quad 2-input NAND, open collector | ??? |
| IC28 | 74LS51 dual 3-input AND-OR-Invert | IC44? |
| IC29 | 74LS32 quad 2-input OR | ??? |
| IC30 | 74LS74 D flip-flop | ??? |
| IC31 | 74LS74 D flip-flop | ??? |
| IC32 | 74LS259 decoder | IC18 |
| IC33 | 74LS04 hex inverter | ??? |
| IC34 | 74LS74 D flip-flop | ??? |
| IC35 | LM324 op-amp | IC93 |
| IC36 | 74LS10 triple 3-input NAND | ??? |
| IC37 | 74LS04 hex inverter | ??? |
| IC38 | 74LS86 quad 2-input XOR | ??? |
| IC39 | 72LS283 4-bit adder | ??? |
| IC40 | 74S00 quad 2-input NAND | ??? |
| IC41 | 74LS02 quad 2-input NOR | ??? |
| IC42 | 74LS163 binary counter | ??? |
| IC43 | 74S04 hex inverter | ??? |
| IC44 | 74LS74 D flip-flop | IC97 |
| IC45 | 74S139 decoder | IC54 |
| IC46 | 74S74 D flip-flop | IC96 |
| IC47 | 74LS86 quad XOR | IC98/99? |
| IC48 | 74LS86 quad XOR | IC98/99? |
| IC49 | 74LS00 quad 2-input NAND | IC89/100? |
| IC50 | 74LS00 quad 2-input NAND | IC89/100? |
| IC51 | MOS ROM | IC71 |
| IC52 | Sideways ROM | IC72-75 |
| IC53 | 4816 RAM (D0 /CAS1) | ??? |
| IC54 | 4816 RAM (D1 /CAS1) | ??? |
| IC55 | 4816 RAM (D2 /CAS1) | ??? |
| IC56 | 4816 RAM (D3 /CAS1) | ??? |
| IC57 | 4816 RAM (D4 /CAS1) | ??? |
| IC58 | 4816 RAM (D5 /CAS1) | ??? |
| IC59 | 4816 RAM (D6 /CAS1) | ??? |
| IC60 | 4816 RAM (D7 /CAS1) | ??? |
| IC61 | 4816 RAM (D0 /CAS0) | ??? |
| IC62 | 4816 RAM (D1 /CAS0) | ??? |
| IC63 | 4816 RAM (D2 /CAS0) | ??? |
| IC64 | 4816 RAM (D3 /CAS0) | ??? |
| IC65 | 4816 RAM (D4 /CAS0) | ??? |
| IC66 | 4816 RAM (D5 /CAS0) | ??? |
| IC67 | 4816 RAM (D6 /CAS0) | ??? |
| IC68 | 4816 RAM (D7 /CAS0) | ??? |
| IC69 | 6522 User VIA | IC17 |
| IC70 | 74LS244 printer buffer | ??? |
| IC71 | 74LS244 1MHz bus buffer | ??? |
| IC72 | 74LS245 1MHz bus transciever | ??? |
| IC73 | PD7002 analog-digital converter | IC90 |
| IC74 | 88LS120 RS423 transciever | IC95 |
| IC75 | DS3691 RS423 driver | IC94 |
| IC76 | 74LS163 binary counter | ??? |
| IC77 | 74LS00 quad 2-input NAND | ??? |
| IC78 | 8271 floppy controller | IC16 |
| IC79 | 7438 quad 2-input NAND, open collector | ??? |
| IC80 | 7438 quad 2-input NAND, open collector | ??? |
| IC81 | 74LS393 4-bit counter | ??? |
| IC82 | 74LS10 triple 3-input NAND | IC36 |
| IC83 | CD4013B CMOS D flip-flop | IC22? |
| IC84 | CD4013B CMOS D flip-flop | IC22? |
| IC85 | CD4020B CMOS binary counter | ??? |
| IC86 | 74LS393 4-bit counter | IC4 |
| IC87 | 74LS123 multivibrator | ??? |
| IC88 | Sideways ROM | IC72-75? |
| IC89 | 68B54 Econet ADLC | IC84 |
| IC90 | Econet clock | not fitted |
| IC91 | 74LS132 quad 2-input NAND, schmitt trigger | ??? |
| IC92 | Econet clock | not fitted |
| IC93 | 75159 differential driver | ??? |
| IC94 | LM319 comparator | ??? |
| IC95 | LM319 comparator | ??? |
| IC96 | 74LS244 Econet station ID buffer | IC90 |
| IC97 | 74LS74 D flip-flop | ??? |
| IC98 | TMS6100 speech chip | IC20 |
| IC99 | TMS5220 phrase ROM | IC21 |
| IC100 | Sideways ROM | IC72-75? |
| IC101 | Sideways ROM | IC72-75? |
