Reply 2640 of 2917, by jaca_kk
640K!enough wrote on 2022-01-28, 03:34:jaca_kk wrote on 2022-01-27, 14:44:
Does the IW78C21M1 part number determine a masked ROM for GUS?
Yes, that holds the ROM-based 1-MiB instrument bank. To my knowledge, there is only one version of that ROM; at least, on every board that has been mentioned here, the ROM contents have been verified to be exactly the same. If another version was ever released, nobody here has ever mentioned it. If you search this thread, you will find the exact UTSource page from which a number of participants have sourced the original ROM. At least so far, nobody has complained of defective chips or different/corrupt content, so as long as the part is still available, that should be a good source.
Thanks a lot for your explanation. The only link I found in this thread didn't work anymore, but they still offer used ROMs -> https://www.utsource.net/itm/p/457141.html
I bought some AM78C201AKC chips on eBay but they got expensive - with import taxes I paid around $30 (USD) for one pcs.
I'm going to design my own low-profile version of the card with built-in DRAM, four 16Mbit (4Mx4) ICs - 8MB total as everything has to be squeezed and also pay some extra attention to the quality of analog part and power supply. I can post this project in the future if anyone would be interested, but I suppose it will take time as this is just my hobby.