Texas Instruments TM124BBK32S-80

Overview

TM124BBK32S-80 from Texas Instruments is a 72-pin single in-line memory module (SIMM) implementing 1,048,576 × 32-bit dynamic RAM using eight TMS44400 4-Mbit DRAMs in plastic SOJ packages. It operates on a single 5-V ±10% supply, delivers 80 ns RAS access time (tRAC), supports distributed 16-ms refresh, and features TTL-compatible I/O with 3-state outputs for use in socketed memory subsystems of early PC/AT-class systems.

For engineers reviewing the TM124BBK32S-80 datasheet, TM124BBK32S-80 pinout, TM124BBK32S-80 application, or TM124BBK32S-80 equivalent, key selection criteria include SIMM form factor compatibility, presence detect pin mapping (PD1–PD4), CAS/RAS timing alignment across four data blocks, and tin-lead contact plating for solder-tabbed assembly.

Technical Context

The TM124BBK32S-80 implements a single-sided, 32-bit-wide DRAM module organized as four independent 1,048,576 × 8 banks, each driven by shared RAS0–RAS3 and CAS0–CAS3 control lines. Address inputs A0–A9 serve all eight underlying TMS44400 DRAMs, enabling row/column multiplexing with common refresh strobing.

All 32 bidirectional data lines (DQ0–DQ31) are 3-state TTL-compatible, with write enable (W) and common CAS control per block ensuring early-write cycle compliance to prevent D/Q bus contention. Presence detect pins PD1–PD4 encode module capacity and speed grade for system BIOS auto-configuration.

Key Specifications

Pinout & Package

72-pin single in-line memory module (SIMM) with tin-lead plated contacts (S-suffix), 1.27 mm substrate thickness, and nickel underplate. Designed for vertical socket insertion with mechanical keying via pin 1 notch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar DRAM module applications.

Compared with TM124BBK32-80, the TM124BBK32S-80 offers identical performance and timing but replaces gold contacts with tin-lead for cost-sensitive, solder-permanent deployments; compared with TM248CBK32S-80, it provides half the capacity at lower power and simpler single-sided footprint - critical for space-constrained AT-class motherboards.

Availability

TM124BBK32S-80 is available at Aetrix Electronics and suitable for PC/AT memory upgrades, industrial PLC expansions, legacy workstation frame buffers, and medical imaging acquisition systems requiring stable component supply and long-lifecycle sourcing.

Supply support for TM124BBK32S-80 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a U.S.-based semiconductor manufacturer founded in 1930, specializing in analog, embedded processing, and memory solutions for industrial, automotive, and computing markets.

The TM124BBK32S-80 belongs to TI's legacy DRAM module product line designed specifically for socket-based memory expansion in 1990s-era x86 systems, emphasizing compatibility, BIOS auto-detection, and robustness under thermal stress.

FAQ

What is the memory organization of the TM124BBK32S-80?

The TM124BBK32S-80 is organized as 1,048,576 words × 32 bits (4 MiB total), implemented using eight TMS44400 4-Mbit DRAMs in SOJ packages. Each TMS44400 is configured as 1,048,576 × 4, and four such devices form one 1,048,576 × 32 bank. The TM124BBK32S-80 uses a single-sided layout with shared A0–A9 addressing and independent RAS/CAS control per 8-bit segment.

Does the TM124BBK32S-80 support CAS-before-RAS refresh?

Yes, the TM124BBK32S-80 supports both RAS-only and CBR (CAS-before-RAS) refresh modes. In CBR mode, CAS is asserted low before RAS, triggering internal refresh counters - allowing the host system to perform refresh without supplying row addresses. The TM124BBK32S-80 requires 1024 refresh cycles within 16 ms regardless of method, and tRCD timing (20 ns min) must be observed during CBR entry.

How does the presence detect (PD) function work on the TM124BBK32S-80?

The TM124BBK32S-80 uses PD1–PD4 pins (pins 67–70) to encode module identity via resistor networks. For the TM124BBK32S-80, PD1 and PD3 are grounded while PD2 and PD4 are open, signaling 1 MiB × 32 capacity and 80 ns speed grade to the host BIOS. This allows automatic configuration without DIP-switch settings - a key feature for plug-and-play memory upgrades in PC/AT platforms.

What is the difference between TM124BBK32S-80 and TM124BBK32-80?

The only difference between TM124BBK32S-80 and TM124BBK32-80 is contact plating: the 'S' suffix denotes tin-lead (solder) plating on the edge connector, while the non-S version uses gold plating. All electrical specifications, timing, pinout, and mechanical dimensions are identical. The TM124BBK32S-80 is intended for wave-soldered or reflow-assembled systems where solder adhesion and cost outweigh repeated insertion durability needs.

Can the TM124BBK32S-80 be used in a system designed for 60 ns or 70 ns modules?

Yes, the TM124BBK32S-80 is backward-compatible with systems specifying TM124BBK32-60 or TM124BBK32-70 modules. Its 80 ns tRAC and 20 ns tCAC meet or exceed the setup/hold and access timing margins required by those faster grades when operated within the same 5-V supply and 0°C–70°C temperature range. System BIOS may report reduced performance, but functional operation is guaranteed.