If you just want to update the 'old' system ROM to fix the Y2K issue, the math bug and/or any other custom mods (e.g. set TELCOM default to 19200bd RS232 instead of the obsolete modem, etc.) then just use a 27C256; it won't interfere with REX or any option ROMs in any way.
If you want to add the function of a single option ROM (e.g. to integrate TS-DOS or SuperROM) then a 27C512 will let you do that at no extra cost or effort in either an 'old' or a 'new' M100; ISTR that there's a fair bit of unused space in the TS-DOS ROM so you might well be able to squeeze some extra functionality in there. With the flying lead connected the upper half of the '512 will indeed occupy the Option ROM memory area and conflict with REX or anything else using that area; disconnecting the lead or connecting it to +5V should disable the Option upper half and be equivalent to using a 27C256, freeing up the Option ROM area for REX or any other option application. And of course if you have the RAM version of REX then you don't need any ROM replacement. Glad to see another user! m ----- Original Message ----- From: "Greg Swallow" <[email protected]> To: <[email protected]> Sent: Saturday, May 05, 2018 12:20 PM Subject: [M100] Mike Stein's PCB vs SuperROM > Confirming what I figure to be true. > > Thanks to my eye sight can not cut my own PCB for 1st Gen M100 Y2K ROMs so > picked up a hand full of Mike Stein's from OSH Park. It is noted that, if the > PCB is fully assembled with a 27C512, it is not compatible with REXX. Am I am > correct in assuming that this would be true for any Option ROM? I have two > M100 with the SuperROM and, though I purchased Mike's PCB to Y2K 3 or 4 1st > Gen M100 I need to sell, I did purchase some extras. If true then I will put > one Stein PCB in my M102 loaded with a Y2K fix image and DVI DOS, TS-DOS too > if I can fit it all, and use the M102 on my DVI. I'm tired of rebuilding DVI > cables anyway. > > Thanks, > > GregS <><
