Yeo Kheng Meng’s DOS port of llama2.c produced 2.08 tokens per second on a 486 DX-2 66 MHz with 32 MB of EDO RAM, using the tiny 260K-parameter TinyStories model. That is a striking retrocomputing demonstration, but it is not Meta’s 7B, 13B, or 70B Llama 2 running on a 486—and the published results measure speed, not energy use.
What the 486 actually ran
The project, dosllam2, is Yeo Kheng Meng’s modified port of Andrej Karpathy’s llama2.c inference code for 32-bit-capable DOS machines. The original project implements inference for the Llama 2 architecture in a single C file and uses FP32 models. To make a language-model demo practical on constrained hardware, Yeo used compact TinyStories checkpoints.
The distinction in model size matters. The 486 result used a 260K-parameter Stories checkpoint. The DOS benchmark table also includes Stories models with 15M, 42M, and 110M parameters. Meta’s Llama 2 model card, by contrast, lists the family at 7B, 13B, and 70B parameters. Calling the demo “Llama 2 on a 486” describes its software lineage, not a run of one of Meta’s full-size models on that machine. Meta’s model card lists the family’s sizes and describes the models as autoregressive transformers.
How fast was it—and what was tested?
Yeo reports throughput in tokens per second. The benchmark conditions specified for the systems below were MS-DOS 6.22 with no memory manager loaded. These are the author’s reported results, not an independent, controlled comparison across modern inference software or hardware.
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| System | CPU, memory | 260K | 15M | 42M | 110M |
| Generic 486 system (1990s) | 486 DX-2 66 MHz; 32 MB EDO | 2.08 tokens/s | Not reported | Not reported | Not reported |
| Toshiba Satellite 315CDT (1996) | Pentium MMX 200 MHz; 96 MB EDO | 15.32 tokens/s | 0.43 tokens/s | Not reported | Not reported |
| Tweener PC (2001) | Pentium III 667 MHz; 512 MB SDRAM | 80.04 tokens/s | 2.35 tokens/s | 0.89 tokens/s | Not reported |
| ThinkPad T42 (2004) | Pentium M 735 1.7 GHz; 2 GB DDR | 331.6 tokens/s | 11.55 tokens/s | 4.42 tokens/s | 1.71 tokens/s |
| ThinkPad X61 (2007) | Core 2 Duo T7300 2.00 GHz; 4 GB DDR2 | 171.89 tokens/s | 5.26 tokens/s | 2.00 tokens/s | 1.00 tokens/s |
| ThinkPad X301 (2008) | Core 2 Duo SU9400 1.4 GHz; 8 GB DDR3 | 171.95 tokens/s | 5.30 tokens/s | 1.98 tokens/s | 0.77 tokens/s |
| ThinkPad X13 Gen 1 (2020) | Core i5-10310U 1.7 GHz; 16 GB DDR4 | 386.36 tokens/s | 10.51 tokens/s | 3.89 tokens/s | 1.53 tokens/s |
| Modern desktop (2024) | Ryzen 5 7600 3.8 GHz; 128 GB DDR5 | 927.27 tokens/s | 15.95 tokens/s | Did not load | Did not load |
For the 2024 Ryzen desktop, Yeo reports that the 42M and 110M models failed to load because of a memory-allocation problem. The author speculates that the DOS extender or protected-mode implementation on that AMD CPU or motherboard may be involved, but does not establish the cause.
Throughput figures are meaningful only alongside the model sizes: the 486’s 2.08 tokens per second is for 260K parameters, while the same table’s larger-model results apply to different machines and workloads. Yeo notes that the T42 outperformed some newer laptops in this setup and produced results similar to the X13 Gen 1. That observation does not establish that it beats newer computers generally; the systems were not matched across software, thermal, or power conditions.
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Why energy claims need a separate measurement
The project write-up reports tokens per second, not watts, total energy, or energy per token. It therefore does not show that a 486 is more energy-efficient than a modern computer. The title’s energy framing is not a measured finding in Yeo’s benchmark data.
How the DOS port works
Yeo used Open Watcom 2.0 beta (the repository specifies the 2025-04-01 build) and a DOS extender to run the program in 32-bit mode. The blog describes selecting the dos32a target and using wcc386 and wlink; the repository directs users to build with wmake. Yeo’s porting write-up details several compatibility changes:
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- Math functions: Because Open Watcom did not provide the expected
sqrtf,powf,cosf,sinf, andexpfsupport, the port wraps available double-precision math functions. - Model loading: The compiler did not support the original memory-mapping approach, so the program reads the model file into memory. This increases initial load time.
- Timing: The original timing calls were unavailable, so the port uses
clock(). - DOS filenames: DOS’s 8.3 filename limit required shortening
tokenizer.bintotokenize.bin.
What you need to try it
The repository’s instructions call for the DOS executable, a tokenizer file, and a compatible Stories model. Follow its naming guidance so files fit DOS’s 8.3 convention, and use a 32-bit-capable DOS environment with the specified extender and compiler toolchain if building from source. The repository also suggests disabling memory managers if allocation problems occur.
Expect some instability: the README says the stories260K model sometimes crashes for unknown reasons. It does not identify a confirmed cause, so the reported 486 speed should be understood as a benchmark result rather than a guarantee of a reliable, general-purpose DOS application.
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