Even More Memories...

Well it seems my detective work was correct. After testing the 512Kb memory expansion that was very kindly sent to me by Neil, I'd come to the conclusion that one of the four DRAM chips was dead.

After posting the blog post to the Amiga Facebook group one of the other guys there offered a DRAM chip to see if I was correct. I gladly accepted and guess what arrived in the post today? Yes, a bill from RS Components. But also, a small envelope with an expertly packed 20pin DRAM chip. Yay!

Well Wrapped DRAM

This DRAM chip is different from the others on the expansion board in a couple of respects. Firstly, it's made by Motorola (just like my phone). Secondly, it is rated at a speed of 70ns. That's a lot faster than the ones on this board which have a speed of 120ns. Hmmm. Not sure if that will make a difference or not..

Just to be sure I found the data sheets for the old DRAM and the new DRAM chips, and checked that they have the same pin out. Which they do. Nice.

Motorola DRAM Pinout

V53C DRAM Pinout (original on board)

So, time to just bite the bullet and put this sucker in there.

New Chip Inserted

Moment of truth....

No magic smoke released. Phew. White screen. OK, patience - there's no internal floppy attached to this test motherboard but there is an external drive. It boots and runs the test disk no problem.

Memory test shows 1.5Mb of total memory, just like before. This time though:

Success!

It works! This has been running through 84 iterations of the memory test with no problems. Nice! Huge thanks to Michael for the DRAM and Neil for the originally broken RAM expansion.

PS Memory test is now over 150 rounds with no faults. Oh, yes. ;)