A dude on eBay has recently sold me a Softec ROM emulator, which I am using to emulate a 27C010 (128Kbyte, 8bit) ROM on an SBC board. The CPU panics immediately, and after two days of digging around, I figured out that the emulated image is not equal to the file I pass to the ROM emulator but rather, and, still worse, it has not a random corruption which can be addressed to the cable, or to the socket, but rather something that always happens at the same address locations
emulated ROM
00900200 56 8A 10 12 48 80 02 80 00 00 00 01 66 04 4E BA V...H.......f.N.
00900210 00 08 4C DF 0C 00 4E 75 48 E7 38 00 28 3C AA AA ..L...NuH.8.(<..
00900220 AA AA 26 3C 55 55 55 55 0C 84 AA AA AA AA 67 04 ..&<UUUU......g.
00900230 4E BA FF 18 0C 83 55 55 55 55 67 04 4E BA FF 0C N.....UUUUg.N...
00900240 13 FC 00 AA 00 4F[02]F0 13 FC 00 55 00 5F[83]F0 .....O.....U._..
00900250 0C 39 00 55 00 4F[00]F0 66 04 74 05 60 16 13 FC .9.U.O..f.t.`...
00900260 00 08 00 1F FF F0 13 FC 00 02 00 7F FF F0 14 39 ...............9
00900270 00 1F[C3]F0 10 02 48 80 48 C0 72 05 B0 41 67 0E ......H.H.r..Ag.
image passed to the ROM emulator
00000200 56 8A 10 12 48 80 02 80 00 00 00 01 66 04 4E BA V...H.......f.N.
00000210 00 08 4C DF 0C 00 4E 75 48 E7 38 00 28 3C AA AA ..L...NuH.8.(<..
00000220 AA AA 26 3C 55 55 55 55 0C 84 AA AA AA AA 67 04 ..&<UUUU......g.
00000230 4E BA FF 18 0C 83 55 55 55 55 67 04 4E BA FF 0C N.....UUUUg.N...
00000240 13 FC 00 AA 00 4F[FF]F0 13 FC 00 55 00 5F[FF]F0 .....O.....U._..
00000250 0C 39 00 55 00 4F[FF]F0 66 04 74 05 60 16 13 FC .9.U.O..f.t.`...
00000260 00 08 00 1F FF F0 13 FC 00 02 00 7F FF F0 14 39 ...............9
00000270 00 1F[FF]F0 10 02 48 80 48 C0 72 05 B0 41 67 0E ......H.H.r..Ag.
(differences are marked within "[", "]" )
Why does it happen? ... This is the big question. This device is a MultiROM device made by Softec Microsystem, and their software comes with a diagnostic, which says "no problem found", but it says lies since we have a serious problem here.
Probably, in my opinion, the diagnostic just tests the cable, or the interface, rather the internal RAM used to store the emulated ROM.