LCD-7: 64-byte data cache lines and a 32 KB instruction cache for LVGL - #17
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Measured with spotapi's remote: full-screen redraw 176 -> 117 ms, a list row 66 -> 44 ms, panel switch 176 -> 146 ms; DMA-capable RAM free 64 -> 48 KB.
bdbarnett
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Sep 25, 2026
On top of #17's 64-byte lines and 32 KB instruction cache. Measured with the board decoding and streaming audio while the LVGL UI runs: full redraw 205 -> 147 ms, panel switch 88 -> 59 ms, 30 list rows built 780 -> 399 ms and laid out 608 -> 335 ms. The same layout is ~216x faster on a desktop: the board is memory-bound and the data cache is the lever. Internal RAM free goes 54 -> 23 KB; a 30-minute soak of real use (about 25 track skips and picks, Wi-Fi streaming, the USB host running) kept a minimum of 17 KB with no allocation failures, Wi-Fi drops or audio stalls. The fragment's header no longer names the applications it was measured with; it describes them.
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Follow-up to #15. Measured with a Spotify remote UI on the panel, no playback: full-screen redraw 176 → 146 ms with 64-byte data cache lines alone (no memory cost), then 117 ms with a 32 KB instruction cache as well. A list row went 66 → 44 ms, and a panel switch 176 → 146 ms. The instruction cache costs 16 KB of internal RAM: DMA-capable free goes from 64 to 48 KB (minimum 45 KB), measured via the audio app's debug endpoint. A 64 KB data cache got rows to 30 ms but left ~13 KB, too little for Wi-Fi to be safe, so it isn't included.