diff --git a/src/rpu.rs b/src/rpu.rs
index a45634c1a3..a42544de67 100644
--- a/src/rpu.rs
+++ b/src/rpu.rs
@@ -2,6 +2,26 @@
 //! 3-stage transaction processing pipeline in software. It listens
 //! for `Request` messages from clients and replies with `Response`
 //! messages.
+//!
+//! ```text
+//!                             .------.
+//!                             | Bank |
+//!                             `---+--`
+//!                                 |
+//!              .------------------|-------------------.
+//!              |  RPU             |                   |
+//!              |                  v                   |
+//!  .---------. |  .-------.  .---------.  .---------. |   .---------.
+//!  |  Alice  |--->|       |  |         |  |         +---->|  Alice  |
+//!  `---------` |  | Fetch |  | Request |  | Respond | |   `---------`
+//!              |  | Stage |->|  Stage  |->|  Stage  | |
+//!  .---------. |  |       |  |         |  |         | |   .---------.
+//!  |   Bob   |--->|       |  |         |  |         +---->|   Bob   |
+//!  `---------` |  `-------`  `---------`  `---------` |   `---------`
+//!              |                                      |
+//!              |                                      |
+//!              `--------------------------------------`
+//! ```
 
 use bank::Bank;
 use packet;
diff --git a/src/tpu.rs b/src/tpu.rs
index 8bf0d6f930..45b898f5c8 100644
--- a/src/tpu.rs
+++ b/src/tpu.rs
@@ -1,5 +1,29 @@
 //! The `tpu` module implements the Transaction Processing Unit, a
 //! 5-stage transaction processing pipeline in software.
+//!
+//! ```text
+//!             .---------------------------------------------------------------.
+//!             |  TPU                                     .-----.              |
+//!             |                                          | PoH |              |
+//!             |                                          `--+--`              |
+//!             |                                             |                 |
+//!             |                                             v                 |
+//!             |  .-------.  .-----------.  .---------.  .--------.  .-------. |
+//! .---------. |  | Fetch |  | SigVerify |  | Banking |  | Record |  | Write | |  .------------.
+//! | Clients |--->| Stage |->|   Stage   |->|  Stage  |->| Stage  |->| Stage +--->| Validators |
+//! `---------` |  |       |  |           |  |         |  |        |  |       | |  `------------`
+//!             |  `-------`  `-----------`  `----+----`  `--------`  `---+---` |
+//!             |                                 |                       |     |
+//!             |                                 |                       |     |
+//!             |                                 |                       |     |
+//!             |                                 |                       |     |
+//!             `---------------------------------|-----------------------|-----`
+//!                                               |                       |
+//!                                               v                       v
+//!                                            .------.               .--------.
+//!                                            | Bank |               | Ledger |
+//!                                            `------`               `--------`
+//! ```
 
 use bank::Bank;
 use banking_stage::BankingStage;