Tandy 2000 - Envision Designs upgrades

[snuci]

I just acquired a Tandy 2000 and was a little surprised when I saw it come up with 896K in the eBay ad but didn't see any extra memory interface cards. I popped out the motherboard and found the Envision Designs 896k memory upgrade and the 8087 Math coprocessor upgrade. I figured someone here would find this interesting as I have read they are uncommon upgrades. Now I need time to researching how to make some boot disks.



(Bigger picture here)

Santo

 

[eeguru]

I did a 800K memory upgrade board for the 2K but it's a replacement for the standard 256K upgrade board that takes up a slot. I'm happy to share that work if anyone is interested. However I was going to wait until I had time to get back to 2K projects and add an IDE type interface to it with a BIOS & DOS upgrade to support it.

I disassembled and reverse annotated the planer BIOS and some of the supplemental BIOS code that is loaded as part of IO.SYS. The former is on Malcom's github. I believe it's possible to make a BIOS replacement that would allow non-Tandy OEM DOS versions to load - maybe even 6.22 or FreeDOS. It would still be a 'work-a-like' in that anything that went directly to hardware would break. But anything that is BIOS/DOS access only would work. I think it's even possible to redirect some soft-interrupt calls so keyboard ISR chaining might also work.