ZX Spectrum ULA: Difference between revisions

Sinclair produced a special batch of Spectrums with an AMI SAGA instead of the Ferranti ULA.  Only one machine belonging to this batch has been found and confirmed as having a genuine AMI SAGA board.  The board was of Issue 6A, mounted in a Spectrum + case, with a sticker instructing that the machine should be sent back to Sinclair Research should it require repair, marked for the attention of the QA manager.  The AMI SAGA was found to run at a much lower temperature than the ULA, and does not require the Spectrum's chroma bias circuitry which was absent from the aforementioned board.  The clock signal is clean enough to drive the Z80 directly, without any amplification, as this is also absent from the special batch board.  One other machine has been reported to be found, but no photographs of this machine have yet been released.