MPS 6540 Commodore PET 2001 ROM Adapter

This adapter allows you to replace a type MPS 6540 ROM in a Commodore PET 2001 with a standard 2716 EPROM.


I have been selling ROM adapters for the Commodore PET-2001 on eBay since 2009. These new Rev. 4 ROM adapters feature:
-Pin-compatibility with the obsolete MPS6540 ROM chips used in the Commodore PET 2001.
-Correct implementation of all five chip select lines on the MPS6540 using a 74HCT138 decoder IC. As with the original part, a low state on the clock pin will also deselect the chip.
Batten and Allen PCB edge pins which exactly replicate the shape of the original DIP pins and thus will work reliably in any DIP socket without damage. No kind of through-hole pin can claim this!
-Only vintage-style though-hole parts so they will not look out of place in a 1977 PET.
-A small footprint and light weight and short design so that the part is unlikely to come loose from the socket if the system is jarred.

You will receive:
– One adapter capable of replacing a single MOS Technologies MPS6540 ROM chip.
– The needed 2716 ROM chip, programmed with the code you need. Please specify the full part number of the original chip when ordering so that I can program the replacement correctly.
– A lifetime guarantee on the adapter. If the adapter does not work in your computer I will work with you until the problem is solved. If the adapter ever fails, just mail it back to me for a free repair.

PLEASE NOTE: These adapters will ONLY work to replace a chip with a part number starting with 6540. They will NOT replace types 2332, 2316, or other ROM types used in Commodore computers other than the original Commodore PET 2001. If you don’t know if you have a bad ROM chip, or if you don’t know which one is bad, you may be interested in my EPROM Programmer Universal Adapter which, when used in conjunction with an inexpensive Willem EPROM programmer, will allow you to read (and therefore test) an MPS6540 ROM chip. You can also read my guide to troubleshooting the Commodore PET 2001 here.

The adapter is about 0.3″ taller than the original 6540 chip and thus may not be mechanically compatible with all 3rd party expansion boards. Please make the appropriate measurements before ordering.

Download the schematic and PCB layout for this product hereNote that these files are available for PERSONAL, NON-COMMERCIAL USE ONLY. In short, you are welcome to use them to build this product yourself, but you must contact me to work out a commission if you wish to sell anything derived from them. This product was designed in ExpressPCB so you will need to download a copy of that software from before you can view the files.

Useful resources:
2716 Datasheet
6540 Pinout
The product page for the original 2009 Rev. 1 version of the adapter is available here.
The product page for the 2013 Rev. 2 and Rev. 3 versions of the adapter is available here.


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