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--- title: RAM Refresh type: test summary: Measures the period and length of the RAM refresh window and which accesses wait for it. category: Hardware tests info: Machine = SCPH-5501 info: Program = SXRAMRF and SXRAMRF2 --- ## Overview SXRAMRF reads root counter 1, counting system clock cycles, before and after a short access. It takes 3000 such samples back to back with interrupts off and the code in the cache. The S sample is a RAM store followed by a load of another RAM word, which waits for the store. The L sample is a RAM load and a NOP, and the N sample is two NOPs with no RAM access. The program counts how often each span occurs and records the time of every sample longer than the commonest span.[^run1] SXRAMRF2 first repeats a load sample until one stalls, which places the code a fixed time after a refresh. It then waits k cycles, for k from 0 to 299, and takes one sample. Its samples are a store then a load (S), a load (L), two stores then a load (W), and a call into three instructions fetched from RAM through KSEG1 (F). Each kind runs its 300 delays three times, and every sample starts from a fresh synchronization.[^run2] ## Results ### Period The RAM is busy once every 256 system clock cycles. Accesses that do not use RAM never wait: all 3000 N samples took 6 cycles. The S and L samples took longer when they met the refresh:[^run1] Table: Span counts over 3000 samples | Sample | Span (cycles) | Samples | | --- | --- | --- | | S | 16 | 2890 | | S | 19 | 55 | | S | 22 | 55 | | L | 11 | 2 | | L | 12 | 2806 | | L | 14 | 192 | | N | 6 | 3000 | ### Length The RAM stays busy for 6 cycles, and a load that arrives during that time waits for its end. A load placed at k 205 took 18 cycles. Each later delay up to k 210 took one cycle less, down to 13, and every other delay took 12. The three passes gave the same figures at every k.[^run2] Table: Sample time against the delay k after a refresh (cycles) | Sample | Without the refresh | Longest with the refresh | Delays affected | | --- | --- | --- | --- | | L, a RAM load | 12 | 18 | 6 | | S, a store then a load | 16 | 26 | 12 | | W, two stores then a load | 18 | 28 | 14 | | F, three uncached fetches | 22 | 28 | 18 | Each RAM access in a sample can be held by the refresh in turn. A sample with more than one RAM access is therefore affected over more delays than a single load.[^run2] ## Runs ### 17 October 2026 (link) [SXRAMRF.txt](/tests/raw/20261017T0103Z-5501a-link/sxramrf/SXRAMRF.txt): ``` SXDEV I_MASK at init 3C040100 SXRAMRF start SXRAMRF S span 16: 2890 SXRAMRF S span 19: 55 SXRAMRF S span 22: 55 SXRAMRF S stall 0: 46286 22 SXRAMRF S stall 7: 46551 19 SXRAMRF S stall 55: 48334 22 SXRAMRF S stall 62: 48599 19 SXRAMRF S stall 110: 50382 22 SXRAMRF S stall 117: 50647 19 SXRAMRF S stall 165: 52430 22 SXRAMRF S stall 172: 52695 19 SXRAMRF S stall 220: 54478 22 SXRAMRF S stall 227: 54743 19 SXRAMRF S stall 275: 56526 22 SXRAMRF S stall 282: 56791 19 SXRAMRF S stall 330: 58574 22 SXRAMRF S stall 337: 58839 19 SXRAMRF S stall 385: 60622 22 SXRAMRF S stall 392: 60887 19 SXRAMRF S stall 440: 62670 22 SXRAMRF S stall 447: 62935 19 SXRAMRF S stall 495: 64718 22 SXRAMRF S stall 502: 64983 19 SXRAMRF S stall 550: 66765 22 SXRAMRF S stall 557: 67030 19 SXRAMRF S stall 605: 68813 22 SXRAMRF S stall 612: 69078 19 SXRAMRF S stall 660: 70861 22 SXRAMRF S stall 667: 71126 19 SXRAMRF S stall 715: 72909 22 SXRAMRF S stall 722: 73174 19 SXRAMRF S stall 770: 74957 22 SXRAMRF S stall 777: 75222 19 SXRAMRF S stall 825: 77005 22 SXRAMRF S stall 832: 77270 19 SXRAMRF S stall 880: 79053 22 SXRAMRF S stall 887: 79318 19 SXRAMRF S stall 935: 81101 22 SXRAMRF S stall 942: 81366 19 SXRAMRF S stall 990: 83149 22 SXRAMRF S stall 997: 83414 19 SXRAMRF S stall 1045: 85197 22 SXRAMRF S stall 1052: 85462 19 SXRAMRF S stall 1100: 87245 22 SXRAMRF S stall 1107: 87510 19 SXRAMRF S stall 1155: 89293 22 SXRAMRF S stall 1162: 89558 19 SXRAMRF S stall 1210: 91341 22 SXRAMRF S stall 1217: 91606 19 SXRAMRF S stall 1265: 93389 22 SXRAMRF S stall 1272: 93654 19 SXRAMRF S stall 1320: 95437 22 SXRAMRF S stall 1327: 95702 19 SXRAMRF S stall 1375: 97485 22 SXRAMRF S stall 1382: 97750 19 SXRAMRF S stall 1430: 99533 22 SXRAMRF S stall 1437: 99798 19 SXRAMRF S stall 1485: 101581 22 SXRAMRF S stall 1492: 101846 19 SXRAMRF S stall 1540: 103629 22 SXRAMRF S stall 1547: 103894 19 SXRAMRF S stall 1595: 105677 22 SXRAMRF S stall 1602: 105942 19 SXRAMRF S stall 1650: 107725 22 SXRAMRF S stall 1657: 107990 19 SXRAMRF S stall 1705: 109773 22 SXRAMRF S stall 1712: 110038 19 SXRAMRF S stall 1760: 111821 22 SXRAMRF S stall 1767: 112086 19 SXRAMRF S stall 1815: 113869 22 SXRAMRF S stall 1822: 114134 19 SXRAMRF S stall 1870: 115917 22 SXRAMRF S stall 1877: 116182 19 SXRAMRF S stall 1925: 117965 22 SXRAMRF S stall 1932: 118230 19 SXRAMRF S stall 1980: 120013 22 SXRAMRF S stall 1987: 120278 19 SXRAMRF S stall 2035: 122061 22 SXRAMRF S stall 2042: 122326 19 SXRAMRF S stall 2090: 124109 22 SXRAMRF S stall 2097: 124374 19 SXRAMRF S stall 2145: 126157 22 SXRAMRF S stall 2152: 126422 19 SXRAMRF S stall 2200: 128205 22 SXRAMRF S stall 2207: 128470 19 SXRAMRF S stall 2255: 130253 22 SXRAMRF S stall 2262: 130518 19 SXRAMRF S stall 2310: 132300 22 SXRAMRF S stall 2317: 132565 19 SXRAMRF S stall 2365: 134348 22 SXRAMRF S stall 2372: 134613 19 SXRAMRF S stall 2420: 136396 22 SXRAMRF S stall 2427: 136661 19 SXRAMRF S stall 2475: 138444 22 SXRAMRF S stall 2482: 138709 19 SXRAMRF S stall 2530: 140492 22 SXRAMRF S stall 2537: 140757 19 SXRAMRF S stall 2585: 142540 22 SXRAMRF S stall 2592: 142805 19 SXRAMRF S stall 2640: 144588 22 SXRAMRF S stall 2647: 144853 19 SXRAMRF S stall 2695: 146636 22 SXRAMRF S stall 2702: 146901 19 SXRAMRF S stall 2750: 148684 22 SXRAMRF S stall 2757: 148949 19 SXRAMRF S stall 2805: 150732 22 SXRAMRF S stall 2812: 150997 19 SXRAMRF S stall 2860: 152780 22 SXRAMRF S stall 2867: 153045 19 SXRAMRF S stall 2915: 154828 22 SXRAMRF S stall 2922: 155093 19 SXRAMRF S stall 2970: 156876 22 SXRAMRF S stall 2977: 157141 19 SXRAMRF S samples 3000 from 46286 to 157962 SXRAMRF L span 11: 2 SXRAMRF L span 12: 2806 SXRAMRF L span 14: 192 SXRAMRF L stall 121: 35256 14 SXRAMRF L stall 136: 35768 14 SXRAMRF L stall 151: 36280 14 SXRAMRF L stall 166: 36792 14 SXRAMRF L stall 181: 37304 14 SXRAMRF L stall 196: 37816 14 SXRAMRF L stall 211: 38328 14 SXRAMRF L stall 226: 38840 14 SXRAMRF L stall 241: 39352 14 SXRAMRF L stall 256: 39864 14 SXRAMRF L stall 271: 40376 14 SXRAMRF L stall 286: 40888 14 SXRAMRF L stall 301: 41400 14 SXRAMRF L stall 316: 41912 14 SXRAMRF L stall 331: 42424 14 SXRAMRF L stall 346: 42936 14 SXRAMRF L stall 361: 43448 14 SXRAMRF L stall 376: 43960 14 SXRAMRF L stall 391: 44472 14 SXRAMRF L stall 406: 44984 14 SXRAMRF L stall 421: 45496 14 SXRAMRF L stall 436: 46008 14 SXRAMRF L stall 451: 46520 14 SXRAMRF L stall 466: 47032 14 SXRAMRF L stall 481: 47544 14 SXRAMRF L stall 496: 48056 14 SXRAMRF L stall 511: 48568 14 SXRAMRF L stall 526: 49080 14 SXRAMRF L stall 541: 49592 14 SXRAMRF L stall 556: 50104 14 SXRAMRF L stall 571: 50616 14 SXRAMRF L stall 586: 51128 14 SXRAMRF L stall 601: 51640 14 SXRAMRF L stall 616: 52152 14 SXRAMRF L stall 631: 52664 14 SXRAMRF L stall 646: 53176 14 SXRAMRF L stall 661: 53688 14 SXRAMRF L stall 676: 54200 14 SXRAMRF L stall 691: 54712 14 SXRAMRF L stall 706: 55224 14 SXRAMRF L stall 721: 55736 14 SXRAMRF L stall 736: 56248 14 SXRAMRF L stall 751: 56760 14 SXRAMRF L stall 766: 57272 14 SXRAMRF L stall 781: 57784 14 SXRAMRF L stall 796: 58296 14 SXRAMRF L stall 811: 58808 14 SXRAMRF L stall 826: 59320 14 SXRAMRF L stall 841: 59832 14 SXRAMRF L stall 856: 60344 14 SXRAMRF L stall 871: 60856 14 SXRAMRF L stall 886: 61368 14 SXRAMRF L stall 901: 61880 14 SXRAMRF L stall 916: 62392 14 SXRAMRF L stall 931: 62904 14 SXRAMRF L stall 946: 63416 14 SXRAMRF L stall 961: 63928 14 SXRAMRF L stall 976: 64440 14 SXRAMRF L stall 991: 64952 14 SXRAMRF L stall 1006: 65464 14 SXRAMRF L stall 1021: 65975 14 SXRAMRF L stall 1036: 66487 14 SXRAMRF L stall 1051: 66999 14 SXRAMRF L stall 1066: 67511 14 SXRAMRF L stall 1081: 68023 14 SXRAMRF L stall 1096: 68535 14 SXRAMRF L stall 1111: 69047 14 SXRAMRF L stall 1126: 69559 14 SXRAMRF L stall 1141: 70071 14 SXRAMRF L stall 1156: 70583 14 SXRAMRF L stall 1171: 71095 14 SXRAMRF L stall 1186: 71607 14 SXRAMRF L stall 1201: 72119 14 SXRAMRF L stall 1216: 72631 14 SXRAMRF L stall 1231: 73143 14 SXRAMRF L stall 1246: 73655 14 SXRAMRF L stall 1261: 74167 14 SXRAMRF L stall 1276: 74679 14 SXRAMRF L stall 1291: 75191 14 SXRAMRF L stall 1306: 75703 14 SXRAMRF L stall 1321: 76215 14 SXRAMRF L stall 1336: 76727 14 SXRAMRF L stall 1351: 77239 14 SXRAMRF L stall 1366: 77751 14 SXRAMRF L stall 1381: 78263 14 SXRAMRF L stall 1396: 78775 14 SXRAMRF L stall 1411: 79287 14 SXRAMRF L stall 1426: 79799 14 SXRAMRF L stall 1441: 80311 14 SXRAMRF L stall 1456: 80823 14 SXRAMRF L stall 1471: 81335 14 SXRAMRF L stall 1486: 81847 14 SXRAMRF L stall 1501: 82359 14 SXRAMRF L stall 1516: 82871 14 SXRAMRF L stall 1531: 83383 14 SXRAMRF L stall 1546: 83895 14 SXRAMRF L stall 1561: 84407 14 SXRAMRF L stall 1576: 84919 14 SXRAMRF L stall 1591: 85431 14 SXRAMRF L stall 1606: 85943 14 SXRAMRF L stall 1621: 86455 14 SXRAMRF L stall 1636: 86967 14 SXRAMRF L stall 1651: 87479 14 SXRAMRF L stall 1666: 87991 14 SXRAMRF L stall 1681: 88503 14 SXRAMRF L stall 1696: 89015 14 SXRAMRF L stall 1711: 89527 14 SXRAMRF L stall 1726: 90039 14 SXRAMRF L stall 1741: 90551 14 SXRAMRF L stall 1756: 91063 14 SXRAMRF L stall 1771: 91575 14 SXRAMRF L stall 1786: 92087 14 SXRAMRF L stall 1801: 92599 14 SXRAMRF L stall 1816: 93111 14 SXRAMRF L stall 1831: 93623 14 SXRAMRF L stall 1846: 94135 14 SXRAMRF L stall 1861: 94647 14 SXRAMRF L stall 1876: 95159 14 SXRAMRF L stall 1891: 95671 14 SXRAMRF L stall 1906: 96183 14 SXRAMRF L stall 1921: 96695 14 SXRAMRF L stall 1936: 97207 14 SXRAMRF L stall 1951: 97719 14 SXRAMRF L stall 1966: 98231 14 SXRAMRF L stall 1981: 98743 14 SXRAMRF L stall 1996: 99255 14 SXRAMRF L stall 2011: 99767 14 SXRAMRF L stall 2026: 100279 14 SXRAMRF L stall 2041: 100791 14 SXRAMRF L stall 2056: 101303 14 SXRAMRF L stall 2071: 101815 14 SXRAMRF L stall 2086: 102327 14 SXRAMRF L stall 2101: 102839 14 SXRAMRF L stall 2116: 103351 14 SXRAMRF L stall 2131: 103863 14 SXRAMRF L stall 2146: 104375 14 SXRAMRF L stall 2161: 104887 14 SXRAMRF L stall 2176: 105399 14 SXRAMRF L stall 2191: 105911 14 SXRAMRF L stall 2206: 106423 14 SXRAMRF L stall 2221: 106935 14 SXRAMRF L stall 2236: 107447 14 SXRAMRF L stall 2251: 107959 14 SXRAMRF L stall 2266: 108471 14 SXRAMRF L stall 2281: 108983 14 SXRAMRF L stall 2296: 109495 14 SXRAMRF L stall 2311: 110007 14 SXRAMRF L stall 2326: 110519 14 SXRAMRF L stall 2341: 111031 14 SXRAMRF L stall 2356: 111543 14 SXRAMRF L stall 2371: 112055 14 SXRAMRF L stall 2386: 112567 14 SXRAMRF L stall 2401: 113079 14 SXRAMRF L stall 2416: 113591 14 SXRAMRF L stall 2431: 114103 14 SXRAMRF L stall 2446: 114615 14 SXRAMRF L stall 2461: 115127 14 SXRAMRF L stall 2476: 115639 14 SXRAMRF L stall 2491: 116151 14 SXRAMRF L stall 2506: 116663 14 SXRAMRF L stall 2521: 117175 14 SXRAMRF L stall 2536: 117687 14 SXRAMRF L stall 2551: 118199 14 SXRAMRF L stall 2566: 118711 14 SXRAMRF L stall 2581: 119223 14 SXRAMRF L stall 2596: 119735 14 SXRAMRF L stall 2611: 120247 14 SXRAMRF L stall 2626: 120759 14 SXRAMRF L stall 2641: 121271 14 SXRAMRF L stall 2656: 121783 14 SXRAMRF L stall 2671: 122295 14 SXRAMRF L stall 2686: 122807 14 SXRAMRF L stall 2701: 123319 14 SXRAMRF L stall 2716: 123831 14 SXRAMRF L stall 2731: 124343 14 SXRAMRF L stall 2746: 124855 14 SXRAMRF L stall 2761: 125367 14 SXRAMRF L stall 2776: 125879 14 SXRAMRF L stall 2791: 126391 14 SXRAMRF L stall 2806: 126903 14 SXRAMRF L stall 2821: 127415 14 SXRAMRF L stall 2836: 127927 14 SXRAMRF L stall 2851: 128439 14 SXRAMRF L stall 2866: 128951 14 SXRAMRF L stall 2881: 129463 14 SXRAMRF L stall 2896: 129975 14 SXRAMRF L stall 2911: 130487 14 SXRAMRF L stall 2926: 130999 14 SXRAMRF L stall 2941: 131510 14 SXRAMRF L stall 2956: 132022 14 SXRAMRF L stall 2971: 132534 14 SXRAMRF L stall 2986: 133046 14 SXRAMRF L samples 3000 from 31139 to 133490 SXRAMRF N span 6: 3000 SXRAMRF N samples 3000 from 38442 to 122416 SXRAMRF end PASS ``` ### 17 October 2026 (link) [SXRAMRF2.txt](/tests/raw/20261017T0108Z-5501a-link/sxramrf2/SXRAMRF2.txt): ``` SXDEV I_MASK at init 3C040100 SXRAMRF2 start SXRAMRF2 sync S 0: 16 12 13 SXRAMRF2 S 0: 16*199 22*1 21*4 26*1 22*1 21*1 20*1 19*1 18*1 17*1 16*89 SXRAMRF2 sync S 1: 16 12 13 SXRAMRF2 S 1: 16*199 22*1 21*4 26*1 22*1 21*1 20*1 19*1 18*1 17*1 16*89 SXRAMRF2 sync S 2: 16 12 13 SXRAMRF2 S 2: 16*199 22*1 21*4 26*1 22*1 21*1 20*1 19*1 18*1 17*1 16*89 SXRAMRF2 sync L 0: 16 12 17 SXRAMRF2 L 0: 12*205 18*1 17*1 16*1 15*1 14*1 13*1 12*89 SXRAMRF2 sync L 1: 16 12 17 SXRAMRF2 L 1: 12*205 18*1 17*1 16*1 15*1 14*1 13*1 12*89 SXRAMRF2 sync L 2: 16 12 17 SXRAMRF2 L 2: 12*205 18*1 17*1 16*1 15*1 14*1 13*1 12*89 SXRAMRF2 sync W 0: 29 12 16 SXRAMRF2 W 0: 18*197 24*1 23*4 28*1 27*1 28*1 24*1 23*1 22*1 21*1 20*1 19*1 18*89 SXRAMRF2 sync W 1: 29 12 16 SXRAMRF2 W 1: 18*197 24*1 23*4 28*1 27*1 28*1 24*1 23*1 22*1 21*1 20*1 19*1 18*89 SXRAMRF2 sync W 2: 29 12 16 SXRAMRF2 W 2: 18*197 24*1 23*4 28*1 27*1 28*1 24*1 23*1 22*1 21*1 20*1 19*1 18*89 SXRAMRF2 sync F 0: 42 12 17 SXRAMRF2 F 0: 22*195 28*1 27*1 26*4 28*1 27*1 26*4 28*1 27*1 26*1 25*1 24*1 23*1 22*87 SXRAMRF2 sync F 1: 42 12 17 SXRAMRF2 F 1: 22*195 28*1 27*1 26*4 28*1 27*1 26*4 28*1 27*1 26*1 25*1 24*1 23*1 22*87 SXRAMRF2 sync F 2: 42 12 17 SXRAMRF2 F 2: 22*34 21*1 22*160 28*1 27*1 26*4 28*1 27*1 26*4 28*1 27*1 26*1 25*1 24*1 23*1 22*83 21*1 22*3 SXRAMRF2 end PASS ``` ## References [^run1]: Hardware test run 20261017T0103Z-5501a-link on the SCPH-5501: [SXRAMRF.txt](/tests/raw/20261017T0103Z-5501a-link/sxramrf/SXRAMRF.txt). [^run2]: Hardware test run 20261017T0108Z-5501a-link on the SCPH-5501: [SXRAMRF2.txt](/tests/raw/20261017T0108Z-5501a-link/sxramrf2/SXRAMRF2.txt).