70 ns access time — what it buys you in a frame buffer
The TMS55161-70DGH is a 256K by 16 video DRAM from Texas Instruments with a 70 ns access time, packaged in a PDSO64. This is the faster bin of the TMS55161 family, shaving 10 ns off the cycle compared to the 80 ns suffix variant. In a graphics frame buffer where the memory bus is the bottleneck, that 10 ns margin lets you tighten the pixel clock timing or run at a higher resolution without redesigning the controller logic. The 256Kx16 organization maps cleanly onto a 16-bit RGB or YUV data path — one chip covers one colour channel per pixel.
Active, but watch the lead-free constraint
No last-time-buy clock is ticking. However, the RoHS compliance flag is marked non-compliant, which means it uses tin-lead solder on the terminations — not the matte-tin finish you get on modern lead-free parts. If your assembly line is RoHS-exempt for legacy repair or military/aerospace work, this is fine. If you need lead-free for new EU-market equipment, you will need to source it under a waiver or look at a RoHS-compliant alternative.
PDSO64 — what you need for the footprint
The PDSO64 is a 64-pin plastic small-outline package, the standard VRAM footprint from that era. Pin pitch and body dimensions match the JEDEC MO-119 outline. If you are replacing a failed part on an existing board, the orientation is marked by pin 1 chamfer on the package body — no lab needed to figure out the orientation. For a new layout, the land pattern is the same as any other 64-pin TSOP-II memory, so the footprint is not exotic.