The Sinclair Spectrum +2 was the first Sinclair computer made by Amstrad after they bought the rights of the Sinclair computers products. Thus, it is not suprising that the Spectrum +2 is very similar in shape and functionality to the Amstrad CPC-464. It was a kind of mix between the Spectrum 128 and the CPC-464 !
Even though it used several features of the CPC-464, such as the built-in tape recorder and a good full-stroke keyboard (at last!), it is above all an improved Spectrum 128. Thus, the sound chip used is still the well-known Yamaha AY-3-8912 which is the sound chip of the MSX computers, Oric computers,Atari ST series) and many other computers of the 80’s. It was the most popular sound chip at the time.
As on the Spectrum 128, two BASIC versions were implemented : the 48k BASIC to remain compatible with the original Sinclair Spectrum, and the 128k BASIC which was already introduced with the Spectrum 128. There was still a calculator mode in the start-menu but the « Tape tester » option of the 128 had been removed since the tape-recorder was built-in.
As with the other 128k models, and due to the limitations of the Z80 CPU which can only address 65536 bytes, the 128kb RAM was not directly usable (unless with bank-switching routines), but could be used as a RAM disk.
There were several models of the Spectrum +2 : the Spectrum +2 (grey case) which had a motherboard nearly identical to that of the 128, and the Spectrum +2A and +2B (black case) which were simply Spectrum +3 computers with a tape-recorder instead of the disk drive. It means that their motherboards were quite similar to that of the +3. The difference between the +2A and +2B was mainly due to a move in production from Hong Kong to Taiwan.
Note that the first ROMs developed by Amstrad for the +2 model caused compatibility problems with the old Spectrum software, so they changed a few things in later ROMs.
When Amstrad conceived the +2A/B and the +3 they redesigned the motherboard and made some internal changes on the bus. They also removed the keypad scanning routines of the Spectrum 128 and +2 (remember the keypad sold with the Spanish Spectrum 128k ?).
Even though it used several features of the CPC-464, such as the built-in tape recorder and a good full-stroke keyboard (at last!), it is above all an improved Spectrum 128. Thus, the sound chip used is still the well-known Yamaha AY-3-8912 which is the sound chip of the MSX computers, Oric computers,Atari ST series) and many other computers of the 80’s. It was the most popular sound chip at the time.
As on the Spectrum 128, two BASIC versions were implemented : the 48k BASIC to remain compatible with the original Sinclair Spectrum, and the 128k BASIC which was already introduced with the Spectrum 128. There was still a calculator mode in the start-menu but the « Tape tester » option of the 128 had been removed since the tape-recorder was built-in.
As with the other 128k models, and due to the limitations of the Z80 CPU which can only address 65536 bytes, the 128kb RAM was not directly usable (unless with bank-switching routines), but could be used as a RAM disk.
There were several models of the Spectrum +2 : the Spectrum +2 (grey case) which had a motherboard nearly identical to that of the 128, and the Spectrum +2A and +2B (black case) which were simply Spectrum +3 computers with a tape-recorder instead of the disk drive. It means that their motherboards were quite similar to that of the +3. The difference between the +2A and +2B was mainly due to a move in production from Hong Kong to Taiwan.
Note that the first ROMs developed by Amstrad for the +2 model caused compatibility problems with the old Spectrum software, so they changed a few things in later ROMs.
When Amstrad conceived the +2A/B and the +3 they redesigned the motherboard and made some internal changes on the bus. They also removed the keypad scanning routines of the Spectrum 128 and +2 (remember the keypad sold with the Spanish Spectrum 128k ?).
Source: www.old-computers.com
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