These are four identical 1GB DDR2 desktop RAM modules (UDIMMs) manufactured by Qimonda (a former memory division of Infineon, which ceased operations around 2009).
Key Specifications (per module):
• Capacity: 1GB
• Type: DDR2 SDRAM
• Form Factor: 240-pin UDIMM (Unbuffered DIMM, for desktop PCs – not laptop SODIMMs)
• Speed: PC2-6400 (DDR2-800 MHz effective clock speed)
• Configuration: 1Rx8 (Single Rank, 8 chips on one side)
• CAS Latency (CL): 6
• Voltage: 1.8V
• ECC: Non-ECC (unbuffered, no error correction)
• Part Number: HYS64T128000EU-2.5-C2
• Additional Label Codes: PC2-6400U-666-12-D0 (common JEDEC/SPD timing code for this speed and latency)
• Assembly Location: Assembled in China (as noted on the stickers)