psx.wiki

RAM Refresh: Difference between revisions

Revision as of 04:48, 23 October 2026
RemmyLee
(Main page: drop the Hardware Tests lede)		Revision as of 05:11, 23 October 2026
RemmyLee
(Hardware tests: 72 more test pages, listed on the main page by area; RUN.toml no longer published)
Line 1:Line 1:
+---
+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).