vargham Posted July 8, 2023 Share Posted July 8, 2023 Hello, I have a Mega 1 with eight 4 bit x 256k SMD DRAM chips on board. I have changed them to 4 bit x 1M chips, I have connected all A9 lines together and to pin 64 of the MMU via 33 Ohm resistor. The computer boots fine. It has German rainbow TOS in ROM. YAART test the memory from 0x8 to 0x011FF1C0 (2 093 504). This is not four megs... There is 2MB ST-RAM when the computer boots from EmuTOS disk. I checked this in SYSINFO program. It shows total ST-RAM: 4096 kbytes and free ST-RAM: 1813 kbytes. It is not good, is it? Quote Link to comment Share on other sites More sharing options...
snarkdluG Posted July 8, 2023 Share Posted July 8, 2023 (edited) Nope. You have only bank 0 found. Only 2Mb of memory. EmuTOS should say 4Mb. Something is wrong. Edited July 8, 2023 by snarkdluG Quote Link to comment Share on other sites More sharing options...
vargham Posted July 9, 2023 Author Share Posted July 9, 2023 Thank you. Why do Sysinfo say 4096k ST-RAM? Before the update Sysinfo displayed 1024k ST-RAM correctly. I checked all traces continuity. RAS(1,2), CAS(1,2,L,H), WE, Address and Data. All good. I will check the high bank's control lines activity during startup. Quote Link to comment Share on other sites More sharing options...
snarkdluG Posted July 9, 2023 Share Posted July 9, 2023 Did you test the chips before soldering them to the board? If not, one is probably bad. Or have gone bad now. If all traces checked okey and it worked previously it must be a new memory chip. Or the 74LS373/74LS244 between MCU and the memory banks. But that seems unlikely since it worked before. Quote Link to comment Share on other sites More sharing options...
vargham Posted July 9, 2023 Author Share Posted July 9, 2023 CAS2 H and L go up on startup and are never pulled down. RAS2 has normal looking activity. Quote Link to comment Share on other sites More sharing options...
vargham Posted July 9, 2023 Author Share Posted July 9, 2023 I have found a bad memory chip. Thank you for your help. Quote Link to comment Share on other sites More sharing options...
snarkdluG Posted July 9, 2023 Share Posted July 9, 2023 👍 No problem. Quote Link to comment Share on other sites More sharing options...
vargham Posted July 9, 2023 Author Share Posted July 9, 2023 Tested all the RAM. All good. Assembled the computer. Only 2MB. Ohh. Maybe a bad connection somewhere? Quote Link to comment Share on other sites More sharing options...
snarkdluG Posted July 9, 2023 Share Posted July 9, 2023 (edited) Could be. Very strange. Cold solder joint somewhere maybe? I hate it when that happens. Intermittent fault is the worst. Could be a chip about to go bad I suppose. So it partially working. Maybe adjust the potentiometer on the PSU to adjust the 5V? If you can't find any fault that is. Do you have steady 5V? Changed caps in PSU? Edited July 9, 2023 by snarkdluG Quote Link to comment Share on other sites More sharing options...
vargham Posted July 11, 2023 Author Share Posted July 11, 2023 On 7/9/2023 at 9:57 PM, snarkdluG said: Cold solder joint somewhere maybe? I have found. So one bad chip and one bad joint. Quote Link to comment Share on other sites More sharing options...
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