Hello Kostas, welcomeI understand that the main chips used were 27128 (16kB) and 27256 (32kB) but they're obsolete.
The chips used were 27128 or 27C128 (both 16K bytes), sometimes for smaller ROMs with less code, 2764 (8K bytes) were used.
As far as I am aware, all 8 bit UV EPROMs with windows for erasing are obsolete. However, One Time Programmable (OTP) EPROMs are still available brand new in a limited number of capacities, the type most suitable for an unmodified BBC B is the AT27C256R-70PU OTP EPROM (32K bytes) that you mention.
If you are happy to modify your machine, a 27C256 can be used to hold two 16K byte ROM images.
The larger 27512 or 27C512 (64K bytes) types can be used (giving four 16K byte ROM images) if your machine is modified.
However, there are used ("pulls") and occasionality new old stock UV EPROMs available on trading sites.
The TL866II Plus has been discontinued.Last but not least, the EPROM programmer: i know that TL866II Plus is a very good one to use, but, as I live in Greece, it's hard to find it here
Yes a T48 programmer should be fine. I don't have one, but another forum member has bought one and was happy.
Mark
Statistics: Posted by 1024MAK — Fri May 16, 2025 11:37 pm