diff --git a/pureboot/README.md b/pureboot/README.md
index fa2f497..b2eae96 100644
--- a/pureboot/README.md
+++ b/pureboot/README.md
@@ -35,9 +35,9 @@ without the trim the same loaders run 10–30 B smaller.
 | ATtiny25 † | 2 KiB | 0x0600 | software | 388 B | 446 B |
 | ATtiny45 † | 4 KiB | 0x0e00 | software | 388 B | 446 B |
 | ATtiny85 † | 8 KiB | 0x1e00 | software | 388 B | 446 B |
-| ATmega8, 8A | 8 KiB | 0x1e00 | USART0 | 358 B | 476 B |
-| ATmega16, 16A | 16 KiB | 0x3e00 | USART0 | 360 B | 480 B |
-| ATmega32, 32A | 32 KiB | 0x7e00 | USART0 | 360 B | 480 B |
+| ATmega8, 8A | 8 KiB | 0x1e00 | USART0 | 362 B | 476 B |
+| ATmega16, 16A | 16 KiB | 0x3e00 | USART0 | 364 B | 480 B |
+| ATmega32, 32A | 32 KiB | 0x7e00 | USART0 | 364 B | 480 B |
 | ATmega48, 48A, 48P, 48PA † | 4 KiB | 0x0e00 | USART0 | 378 B | 450 B |
 | ATmega88, 88A, 88P, 88PA | 8 KiB | 0x1e00 | USART0 | 388 B | 460 B |
 | ATmega168, 168A, 168P, 168PA | 16 KiB | 0x3e00 | USART0 | 390 B | 464 B |
diff --git a/pureboot/pureboot.cpp b/pureboot/pureboot.cpp
index 11f1726..96671df 100644
--- a/pureboot/pureboot.cpp
+++ b/pureboot/pureboot.cpp
@@ -172,10 +172,12 @@ struct hardware_link {
 	using uart = avr::uart::usart<usart_unit, C, {.baud = B, .max_baud_error = 2.5_pct}>;
 
 	// The compiled idle poll around the window's narrow (uint24_t) countdown:
-	// lds UCSR0A (2), sbrc skipping the exit (2), sbiw + sbci + brne (5).
-	// A uint32_t countdown pays one more sbci — window_polls() adds it where
-	// the count forces the wide type. Held by the pureboot.window gate.
-	static constexpr std::uint8_t poll_cycles = 9;
+	// the RXC test, then sbiw + sbci + brne (5). The test's cost follows the
+	// status register's home — a 2-cycle bit-skip where UCSRnA sits in
+	// bit-addressable I/O (the classic megas), lds + skip (4) in extended
+	// I/O. A uint32_t countdown pays one more sbci — window_polls() adds it
+	// where the count forces the wide type. Held by the pureboot.window gate.
+	static constexpr std::uint8_t poll_cycles = avr::hw::usart_of<usart_unit>::ucsra::addr < 0x40 ? 7 : 9;
 
 	static void init()
 	{