Acorn ARM250TG ARM2aS system-on-chip.
ARM2aS core, VIDC, MEMC and IOC on a single chip. Effectively a single-chip Acorn Archimedes, just add ROM, RAM and storage.
Package
Acorn [Acorn logo] 0294,030 ARM250TG GPS ARM 9350B PS[Triangle ESD symbol]
The GPS (later Mitel, then Zarlink) topmark format is documented in this Conexant PCN.
In the context of this part, “PS” likely indicates the Plessey Semiconductors site at Cheney Manor, a manufacture date of week 50 of 1993, and the triangle indicates the part is sensitive to ESD (i.e. likely a CMOS process).
Decap
Thermal hot air with mechanical assistance (“Chips a la Antoine), 852A solder station with air and temperature set to maximum (450C). Die was damaged during removal which chipped the bottom left corner. The GEC Plessey logo was present on the chip but couldn't be imaged.
An attempt was made to remove the polyimide topcoat with an actively-cooled PC heatsink and small kitchen torch - this was successful but mishandling on my part cracked the die.
The die is quite large, around 10mm square, and must have been very expensive to produce.
Mastodon thread with some photos of the process: https://digipres.club/@philpem/112620630504333892
