Blog

23256 ROM-el

23256 ROM-el PCB
23256 ROM-el PCB

23128 and 23256 ROMs are not as hard to deal with, as 27XXX JEDEC standard EPROMs share the same pinout.  However, some of the benefits of the 2364 ROM-el still remain, such as:

  • Use of 5V programmable FLASH/EEPROM
  • Can be pre-assembled and field programmed

If used in a switched ROM scenario (one where the upper address bits are toggled on or off via a switch), this design can save a lot of time (most 27256/27512 switched ROM replacement options I’ve seen manually bend the additional address pins over the top of the EPROM and hand solder a resistor to Vcc.)

Thus, I’m considering this unit as well for production.  It offers some additional configuration options over the 2364 ROM-el, but retains the ease of assembly and programming of the 2364 ROM-el.

ROM-el ROM Eliminator

ROM-el ROM Eliminator
ROM-el ROM Eliminator

Another project of mine requires a way to replace the 2364 ROMs on Commodore computers, so I started looking for a 2764 to 2364 adapter. After designing one, I determined that DIP EPROMs are starting to get very expensive, so I set about designing a Flash version. My tentative name is ROM-el. Since Flash is considered ROM as well, the name is a bit off, but I liked it, and only the pedantic will probably care.

64NIC+ Out for Production

64NIC+ top view
64NIC+ top view

2 64NIC+ boards arrived on April 20, and I assembled one in the evening. Initial testing with Devia’s NIC-Test was unsuccessful, so I gave up for the night. After work on the 21st, I pored over the schematics and determined I had miscopied a resistor layout from Eric Pratt’s 64NIC design. The resistor must be tied to ground, not Vcc. Dubious that such a small change would make the board work, I nonetheless made the change and …. it did nothing.

I decided I’d ruined one board, so I assembled the second board, taking care to make the resistor mod before plugging it in. Devia’s NIC-Test worked immediately. Later, I tried the apparently ruined board and it also worked, so it appears I did not completely ruin the board.

Given the success, I immediately released the board to production that evening.