--- a/src/devices/machine/z80scc.cpp
+++ b/src/devices/machine/z80scc.cpp
@@ -1045,7 +1045,18 @@
 
 	m_uart->m_wr0_ptrbits = 0;
 
-	m_rx_fifo_sz = (m_uart->m_variant & z80scc_device::SET_ESCC) ? 8 : 3;
+	// RetroNet patch: see z80scc.h. JOEY_Z80SCC_RX_FIFO=N sets the depth, clamped to 3..512
+	// (3 = real Z8530; an ESCC keeps at least its real 8). Unset, it is the whole 512.
+	m_rx_fifo_sz = std::size(m_rx_data_fifo);
+	if (char const *const depth = osd_getenv("JOEY_Z80SCC_RX_FIFO"); depth && *depth)
+	{
+		m_rx_fifo_sz = std::clamp(atoi(depth), 3, m_rx_fifo_sz);
+		if (m_uart->m_variant & z80scc_device::SET_ESCC)
+		{
+			m_rx_fifo_sz = std::max(m_rx_fifo_sz, 8);
+		}
+		osd_printf_info("%s: RX FIFO depth %d (JOEY_Z80SCC_RX_FIFO)\n", tag(), m_rx_fifo_sz);
+	}
 
 	m_tx_fifo_sz = (m_uart->m_variant & z80scc_device::SET_ESCC) ? 4 : 1;
 
--- a/src/devices/machine/z80scc.h
+++ b/src/devices/machine/z80scc.h
@@ -256,8 +256,12 @@
 	unsigned int m_delayed_tx_brg_change;
 
 	// receiver state
-	uint8_t m_rx_data_fifo[8];    // receive data FIFO
-	uint8_t m_rx_error_fifo[8];   // receive error FIFO
+	// RetroNet patch: widened from 8 so a POLLED receiver (no RX interrupt) survives its deaf
+	// windows under emulation. The depth in use is m_rx_fifo_sz: all 512 unless the
+	// JOEY_Z80SCC_RX_FIFO environment variable sets it (3 = real silicon, where clients need
+	// interrupt RX). See device_start().
+	uint8_t m_rx_data_fifo[512];    // receive data FIFO
+	uint8_t m_rx_error_fifo[512];   // receive error FIFO
 	uint8_t m_rx_error;       // current receive error
 	//int m_rx_fifo         // receive FIFO pointer
 	int m_rx_fifo_rp;       // receive FIFO read pointer