{"id":1405,"date":"2026-02-26T10:25:00","date_gmt":"2026-02-26T01:25:00","guid":{"rendered":"https:\/\/rtlearner.com\/?p=1405"},"modified":"2026-02-26T10:50:04","modified_gmt":"2026-02-26T01:50:04","slug":"fpga-power-analysis-saif-file-vivado","status":"publish","type":"post","link":"https:\/\/rtlearner.com\/en\/fpga-power-analysis-saif-file-vivado\/","title":{"rendered":"[FPGA Practical Design] Finding the Real Power Consumption with SAIF Files"},"content":{"rendered":"<p>When designing an NPU at a low-power AI semiconductor startup, you stake your life on the goal of \"achieving maximum performance with minimum power.\" After finishing the RTL coding and successfully running Synthesis and Implementation, you nervously click the <strong>Report Power<\/strong> button in Vivado.<\/p>\n\n\n\n<p>Have you ever been horrified to see the result window proudly display: <strong>Total On-Chip Power: 200 W<\/strong>?<\/p>\n\n\n\n<p>Every hardware engineer has probably felt a chill down their spine at least once, thinking, \"My low-power architecture is burning 50W? Is the chip going to melt?\" Especially if you are targeting a massive, aircraft-carrier-sized chip like the Versal VP1902, this number feels incredibly threatening.<\/p>\n\n\n\n<p class=\"translation-block\">But don't despair just yet. Today, we will uncover the trap of Vivado's power estimation and learn how to find the 'true' power consumption using SAIF files extracted from simulation data.<\/p>\n\n\n<style>.kb-table-of-content-nav.kb-table-of-content-id1405_3fad77-27 .kb-table-of-content-wrap{padding-top:var(--global-kb-spacing-sm, 1.5rem);padding-right:var(--global-kb-spacing-sm, 1.5rem);padding-bottom:var(--global-kb-spacing-sm, 1.5rem);padding-left:var(--global-kb-spacing-sm, 1.5rem);box-shadow:0px 0px 14px 0px rgba(0, 0, 0, 0.2);}.kb-table-of-content-nav.kb-table-of-content-id1405_3fad77-27 .kb-table-of-contents-title-wrap{padding-top:0px;padding-right:0px;padding-bottom:0px;padding-left:0px;}.kb-table-of-content-nav.kb-table-of-content-id1405_3fad77-27 .kb-table-of-contents-title{font-weight:regular;font-style:normal;}.kb-table-of-content-nav.kb-table-of-content-id1405_3fad77-27 .kb-table-of-content-wrap .kb-table-of-content-list{font-weight:regular;font-style:normal;margin-top:var(--global-kb-spacing-sm, 1.5rem);margin-right:0px;margin-bottom:0px;margin-left:0px;}@media all and (max-width: 767px){.kb-table-of-content-nav.kb-table-of-content-id1405_3fad77-27 .kb-table-of-contents-title{font-size:var(--global-kb-font-size-md, 1.25rem);}.kb-table-of-content-nav.kb-table-of-content-id1405_3fad77-27 .kb-table-of-content-wrap .kb-table-of-content-list{font-size:var(--global-kb-font-size-sm, 0.9rem);}}<\/style>\n\n<style>.kadence-column1405_167e51-50 > .kt-inside-inner-col{box-shadow:0px 0px 14px 0px rgba(0, 0, 0, 0.2);}.kadence-column1405_167e51-50 > .kt-inside-inner-col,.kadence-column1405_167e51-50 > .kt-inside-inner-col:before{border-top-left-radius:0px;border-top-right-radius:0px;border-bottom-right-radius:0px;border-bottom-left-radius:0px;}.kadence-column1405_167e51-50 > .kt-inside-inner-col{column-gap:var(--global-kb-gap-sm, 1rem);}.kadence-column1405_167e51-50 > .kt-inside-inner-col{flex-direction:column;}.kadence-column1405_167e51-50 > .kt-inside-inner-col > .aligncenter{width:100%;}.kadence-column1405_167e51-50 > .kt-inside-inner-col:before{opacity:0.3;}.kadence-column1405_167e51-50{position:relative;}@media all and (max-width: 1024px){.kadence-column1405_167e51-50 > .kt-inside-inner-col{flex-direction:column;justify-content:center;}}@media all and (max-width: 767px){.kadence-column1405_167e51-50 > .kt-inside-inner-col{flex-direction:column;justify-content:center;}}<\/style>\n<div class=\"wp-block-kadence-column kadence-column1405_167e51-50\"><div class=\"kt-inside-inner-col\">\n<p><strong>Related articles<\/strong><\/p>\n\n\n\n<p>\u2705<a href=\"https:\/\/rtlearner.com\/en\/fpga-bram-initialization-readmemh-cell-properties\/\" data-type=\"post\" data-id=\"1390\">FPGA Practical Design - The Ultimate Guide to BRAM Initialization<\/a><\/p>\n\n\n\n<p>\u2705<a href=\"https:\/\/rtlearner.com\/en\/vivado-troubleshooting-logic-pruning-tool-crash\/\" data-type=\"post\" data-id=\"1396\">Vivado Troubleshooting - Preventing Pruning and Solving Tool Crashes<\/a><\/p>\n\n\n\n<p>\u2705<a href=\"https:\/\/rtlearner.com\/en\/fpga-hardware-optimization-fixed-point-dsp-slice\/\" data-type=\"post\" data-id=\"1400\">Hardware Optimization - Float to Integer<\/a><\/p>\n<\/div><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">1. The Culprit Behind 200W: Vectorless Estimation and the Thermal Butterfly Effect<\/h2>\n\n\n\n<p>If you look closely at a 200W+ power report, you'll notice something very strange:<\/p>\n\n\n<style>.kb-image1405_34b8ae-6a.kb-image-is-ratio-size, .kb-image1405_34b8ae-6a .kb-image-is-ratio-size{max-width:700px;width:100%;}.wp-block-kadence-column > .kt-inside-inner-col > .kb-image1405_34b8ae-6a.kb-image-is-ratio-size, .wp-block-kadence-column > .kt-inside-inner-col > .kb-image1405_34b8ae-6a .kb-image-is-ratio-size{align-self:unset;}.kb-image1405_34b8ae-6a figure{max-width:700px;}.kb-image1405_34b8ae-6a .image-is-svg, .kb-image1405_34b8ae-6a .image-is-svg img{width:100%;}.kb-image1405_34b8ae-6a .kb-image-has-overlay:after{opacity:0.3;}@media all and (max-width: 767px){.kb-image1405_34b8ae-6a.kb-image-is-ratio-size, .kb-image1405_34b8ae-6a .kb-image-is-ratio-size{max-width:290px;width:100%;}.kb-image1405_34b8ae-6a figure{max-width:290px;}}<\/style>\n<div class=\"wp-block-kadence-image kb-image1405_34b8ae-6a\"><figure class=\"aligncenter size-full\"><img data-dominant-color=\"e9ebe8\" data-has-transparency=\"false\" style=\"--dominant-color: #e9ebe8;\" loading=\"lazy\" decoding=\"async\" width=\"936\" height=\"450\" src=\"https:\/\/rtlearner.com\/wp-content\/uploads\/2026\/02\/image.jpg\" alt=\"\" class=\"kb-img wp-image-1406 not-transparent\" srcset=\"https:\/\/rtlearner.com\/wp-content\/uploads\/2026\/02\/image.jpg 936w, https:\/\/rtlearner.com\/wp-content\/uploads\/2026\/02\/image-300x144.jpg 300w, https:\/\/rtlearner.com\/wp-content\/uploads\/2026\/02\/image-768x369.jpg 768w, https:\/\/rtlearner.com\/wp-content\/uploads\/2026\/02\/image-18x9.jpg 18w\" sizes=\"auto, (max-width: 936px) 100vw, 936px\" \/><\/figure><\/div>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Dynamic Power:<\/strong> 200 W<\/li>\n\n\n\n<li><strong>Device Static (Leakage Power):<\/strong> 48 W<\/li>\n\n\n\n<li><strong>Junction Temperature:<\/strong> 100.0\u00b0C (Reached the absolute limit)<\/li>\n<\/ul>\n\n\n\n<p>What is the truth behind these numbers? It means, \"The tool thinks the chip is boiling at 100 degrees, causing semiconductor leakage current to explode exponentially.\" So, why did the tool conclude the chip reached 100 degrees?<\/p>\n\n\n\n<p>When Vivado has no information about your actual input data, it estimates power using a default mode called Vectorless. This mode assumes the absolute worst-case scenario: \"Every single signal and flip-flop is frantically toggling at a constant probability (usually 12.5%).\" This fake switching activity generates unnecessary Dynamic Power, which raises the junction temperature, which in turn generates massive Static Power. It is a vicious butterfly effect.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">2. SAIF (Switching Activity Interchange Format)<\/h2>\n\n\n\n<p>Think about the actual operation of an AI accelerator (MAC array). There are countless moments when a 0 is multiplied, or the Enable signal is off because there's no incoming data (Idle states). In other words, Vivado's assumption that all circuits are constantly firing at 12.5% is completely wrong.<\/p>\n\n\n\n<p>To clear your name, you must provide Vivado with evidence: \"Look, my circuit actually operates this quietly!\" That evidence is the <strong>SAIF file<\/strong>. A SAIF file is a text file that records the actual toggle count (0 to 1, 1 to 0 transitions) of all signals during a simulation run.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">3. Extracting and Applying SAIF via the Tcl Console<\/h2>\n\n\n\n<p>SAIF files are not generated automatically. Because they can grow to gigabytes (GB) in size, the user must explicitly command the tool to record them using Tcl commands.<\/p>\n\n\n\n<p><strong>Step 1: Run Behavioral Simulation and Wait<\/strong><\/p>\n\n\n\n<p>Click Run Behavioral Simulation in the GUI to open the simulator. When the waveform window appears, do not press the Run (Play) button at the top yet. Stay at 0ns.<\/p>\n\n\n\n<p><strong>Step 2: Enter Extraction Commands in the Tcl Console<\/strong><\/p>\n\n\n\n<div class=\"wp-block-kevinbatdorf-code-block-pro\" data-code-block-pro-font-family=\"Code-Pro-JetBrains-Mono\" style=\"font-size:.875rem;font-family:Code-Pro-JetBrains-Mono,ui-monospace,SFMono-Regular,Menlo,Monaco,Consolas,monospace;line-height:1.25rem;--cbp-tab-width:2;tab-size:var(--cbp-tab-width, 2)\"><span style=\"display:block;padding:16px 0 0 16px;margin-bottom:-1px;width:100%;text-align:left;background-color:#2e3440ff\"><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"54\" height=\"14\" viewbox=\"0 0 54 14\"><g fill=\"none\" fill-rule=\"evenodd\" transform=\"translate(1 1)\"><circle cx=\"6\" cy=\"6\" r=\"6\" fill=\"#FF5F56\" stroke=\"#E0443E\" stroke-width=\".5\"><\/circle><circle cx=\"26\" cy=\"6\" r=\"6\" fill=\"#FFBD2E\" stroke=\"#DEA123\" stroke-width=\".5\"><\/circle><circle cx=\"46\" cy=\"6\" r=\"6\" fill=\"#27C93F\" stroke=\"#1AAB29\" stroke-width=\".5\"><\/circle><\/g><\/svg><\/span><span role=\"button\" tabindex=\"0\" style=\"color:#d8dee9ff;display:none\" aria-label=\"Copy\" class=\"code-block-pro-copy-button\"><pre class=\"code-block-pro-copy-button-pre\" aria-hidden=\"true\"><textarea class=\"code-block-pro-copy-button-textarea\" tabindex=\"-1\" aria-hidden=\"true\" readonly># 1. \uae30\ub85d\ud560 SAIF \ud30c\uc77c \uc0dd\uc131 (\uc774\ub984 \uc9c0\uc815)\nopen_saif \"power_data.saif\"\n\n# 2. \uae30\ub85d\ud560 \ubc94\uc704 \uc124\uc815 (\ud14c\uc2a4\ud2b8\ubca4\uce58 \ud558\uc704\uc758 \ubaa8\ub4e0 \uac1d\uccb4\ub97c \uc7ac\uadc0\uc801\uc73c\ub85c \ud3ec\ud568)\nlog_saif &#91;get_objects -r *&#93;\n\n# 3. \uc2dc\ubbac\ub808\uc774\uc158 \uc2e4\ud589 (\uc2e4\uc81c \ub3d9\uc791\uc774 \ucda9\ubd84\ud788 \uc77c\uc5b4\ub0a0 \uc2dc\uac04\ub9cc\ud07c)\nrun 10us\n\n# 4. \ud30c\uc77c \ub2eb\uae30 \ubc0f \uc800\uc7a5 (\uc774 \uba85\ub839\uc5b4\ub97c \uccd0\uc57c \ud30c\uc77c\uc774 \ub514\uc2a4\ud06c\uc5d0 \uc368\uc9d1\ub2c8\ub2e4!)\nclose_saif<\/textarea><\/pre><svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" style=\"width:24px;height:24px\" fill=\"none\" viewbox=\"0 0 24 24\" stroke=\"currentColor\" stroke-width=\"2\"><path class=\"with-check\" stroke-linecap=\"round\" stroke-linejoin=\"round\" d=\"M9 5H7a2 2 0 00-2 2v12a2 2 0 002 2h10a2 2 0 002-2V7a2 2 0 00-2-2h-2M9 5a2 2 0 002 2h2a2 2 0 002-2M9 5a2 2 0 012-2h2a2 2 0 012 2m-6 9l2 2 4-4\"><\/path><path class=\"without-check\" stroke-linecap=\"round\" stroke-linejoin=\"round\" d=\"M9 5H7a2 2 0 00-2 2v12a2 2 0 002 2h10a2 2 0 002-2V7a2 2 0 00-2-2h-2M9 5a2 2 0 002 2h2a2 2 0 002-2M9 5a2 2 0 012-2h2a2 2 0 012 2\"><\/path><\/svg><\/span><pre class=\"shiki nord\" style=\"background-color: #2e3440ff\" tabindex=\"0\"><code><span class=\"line\"><span style=\"color: #616E88\"># 1. Create the SAIF file to record (name it as you like)<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">open_saif <\/span><span style=\"color: #ECEFF4\">&quot;<\/span><span style=\"color: #A3BE8C\">power_data.saif<\/span><span style=\"color: #ECEFF4\">&quot;<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #616E88\"># 2. Set the scope to record (recursively include all objects under the testbench)<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">log_saif &#91;get_objects -r *&#93;<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #616E88\"># 3. Run the simulation (for enough time to capture realistic activity)<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">run <\/span><span style=\"color: #B48EAD\">1<\/span><span style=\"color: #D8DEE9FF\">0us<\/span><\/span>\n<span class=\"line\"><\/span>\n<span class=\"line\"><span style=\"color: #616E88\"># 4. Close and save the file (Crucial: The file is written to disk only after this command!)<\/span><\/span>\n<span class=\"line\"><span style=\"color: #D8DEE9FF\">close_saif<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n<p><strong>Step 3: Apply SAIF to Report Power<\/strong><\/p>\n\n\n\n<p>Now, open your Implemented Design and click Report Power again. Navigate to the <strong>Switching<\/strong> tab in the settings window. In the <strong>Simulation Activity File (SAIF)<\/strong> field, browse and select the power_data.saif file you just extracted, then click OK.<\/p>\n\n\n\n<p>How did the results change? By reflecting the actual switching rates, the Dynamic Power drops to a realistic level. As the heat generation decreases, the temperature normalizes from 100 degrees down to 60~70 degrees, and as a result, <strong>Device Static Power plummets dramatically<\/strong>. You will experience the magic of that 200W figure shrinking down to a realistic wattage suitable for the chip's baseline (e.g., 50W).<\/p>\n\n\n<style>.kb-image1405_4a1a1c-71.kb-image-is-ratio-size, .kb-image1405_4a1a1c-71 .kb-image-is-ratio-size{max-width:700px;width:100%;}.wp-block-kadence-column > .kt-inside-inner-col > .kb-image1405_4a1a1c-71.kb-image-is-ratio-size, .wp-block-kadence-column > .kt-inside-inner-col > .kb-image1405_4a1a1c-71 .kb-image-is-ratio-size{align-self:unset;}.kb-image1405_4a1a1c-71 figure{max-width:700px;}.kb-image1405_4a1a1c-71 .image-is-svg, .kb-image1405_4a1a1c-71 .image-is-svg img{width:100%;}.kb-image1405_4a1a1c-71 .kb-image-has-overlay:after{opacity:0.3;}@media all and (max-width: 767px){.kb-image1405_4a1a1c-71.kb-image-is-ratio-size, .kb-image1405_4a1a1c-71 .kb-image-is-ratio-size{max-width:290px;width:100%;}.kb-image1405_4a1a1c-71 figure{max-width:290px;}}<\/style>\n<div class=\"wp-block-kadence-image kb-image1405_4a1a1c-71\"><figure class=\"aligncenter size-full\"><img data-dominant-color=\"edf1f2\" data-has-transparency=\"false\" style=\"--dominant-color: #edf1f2;\" loading=\"lazy\" decoding=\"async\" width=\"932\" height=\"395\" src=\"https:\/\/rtlearner.com\/wp-content\/uploads\/2026\/02\/image-2.jpg\" alt=\"Power summary\" class=\"kb-img wp-image-1407 not-transparent\" srcset=\"https:\/\/rtlearner.com\/wp-content\/uploads\/2026\/02\/image-2.jpg 932w, https:\/\/rtlearner.com\/wp-content\/uploads\/2026\/02\/image-2-300x127.jpg 300w, https:\/\/rtlearner.com\/wp-content\/uploads\/2026\/02\/image-2-768x325.jpg 768w, https:\/\/rtlearner.com\/wp-content\/uploads\/2026\/02\/image-2-18x8.jpg 18w\" sizes=\"auto, (max-width: 932px) 100vw, 932px\" \/><figcaption>Power summary<\/figcaption><\/figure><\/div>\n\n\n\n<p>(Note: A massive chip like the Versal 1902 has a high baseline static power, so it won't drop to 0W).<\/p>\n\n\n<style>.kadence-column1405_20abdd-bb > .kt-inside-inner-col{box-shadow:0px 0px 14px 0px rgba(0, 0, 0, 0.2);}.kadence-column1405_20abdd-bb > .kt-inside-inner-col,.kadence-column1405_20abdd-bb > .kt-inside-inner-col:before{border-top-left-radius:0px;border-top-right-radius:0px;border-bottom-right-radius:0px;border-bottom-left-radius:0px;}.kadence-column1405_20abdd-bb > .kt-inside-inner-col{column-gap:var(--global-kb-gap-sm, 1rem);}.kadence-column1405_20abdd-bb > .kt-inside-inner-col{flex-direction:column;}.kadence-column1405_20abdd-bb > .kt-inside-inner-col > .aligncenter{width:100%;}.kadence-column1405_20abdd-bb > .kt-inside-inner-col:before{opacity:0.3;}.kadence-column1405_20abdd-bb{position:relative;}@media all and (max-width: 1024px){.kadence-column1405_20abdd-bb > .kt-inside-inner-col{flex-direction:column;justify-content:center;}}@media all and (max-width: 767px){.kadence-column1405_20abdd-bb > .kt-inside-inner-col{flex-direction:column;justify-content:center;}}<\/style>\n<div class=\"wp-block-kadence-column kadence-column1405_20abdd-bb\"><div class=\"kt-inside-inner-col\">\n<p><strong>Related articles<\/strong><\/p>\n\n\n\n<p>\u2705<a href=\"https:\/\/rtlearner.com\/en\/fpga-bram-initialization-readmemh-cell-properties\/\" data-type=\"post\" data-id=\"1390\">FPGA Practical Design - The Ultimate Guide to BRAM Initialization<\/a><\/p>\n\n\n\n<p>\u2705<a href=\"https:\/\/rtlearner.com\/en\/vivado-troubleshooting-logic-pruning-tool-crash\/\" data-type=\"post\" data-id=\"1396\">Vivado Troubleshooting - Preventing Pruning and Solving Tool Crashes<\/a><\/p>\n\n\n\n<p>\u2705<a href=\"https:\/\/rtlearner.com\/en\/fpga-hardware-optimization-fixed-point-dsp-slice\/\" data-type=\"post\" data-id=\"1400\">Hardware Optimization - Float to Integer<\/a><\/p>\n<\/div><\/div>\n\n\n\n<p>References: <a href=\"https:\/\/docs.amd.com\/r\/en-US\/ug907-vivado-power-analysis-optimization\/Navigating-Content-by-Design-Process\" target=\"_blank\" rel=\"noopener\">AMD<\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>When designing an NPU at a low-power AI semiconductor startup, you stake your life on the goal of \"achieving maximum performance with minimum power.\"<\/p>","protected":false},"author":1,"featured_media":1407,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_kadence_starter_templates_imported_post":false,"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_kad_post_classname":"","footnotes":""},"categories":[8],"tags":[10,36],"class_list":["post-1405","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-fpga","tag-fpga","tag-vivado"],"_links":{"self":[{"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/posts\/1405","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/comments?post=1405"}],"version-history":[{"count":4,"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/posts\/1405\/revisions"}],"predecessor-version":[{"id":1414,"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/posts\/1405\/revisions\/1414"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/media\/1407"}],"wp:attachment":[{"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/media?parent=1405"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/categories?post=1405"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rtlearner.com\/en\/wp-json\/wp\/v2\/tags?post=1405"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}<!-- This website is optimized by Airlift. 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