Polymorph wrote:
On Feb 9, 11:51 am, A2Pro <a...@wilserv.com> wrote:Hey, Alex! On Feb 8, 4:55 pm, Alex wrote:Did you try the obvious: DigiKey? I got mine from there last week. P/N 269-3901-ND Even if everybody who got my kit decided to buy one, they probably still have a few left :)
So, you have a 20 MHz part. Before we go nuts arranging a group buy, tell us, does it work in your card? Any mods needed to the card to get it to fully utilize this speed demon?
I'm wondering how Alex was lucky enough to get an item that DigiKey shows as non-stock. And, yes, I'd also like to know if it works!
As I'm an owner of an original Applicard, I am also curious if people think that the original Applicard could be modded to run at 20Mhz, or if the older design has some limitations that do not allow such ambitious undertakings.
That would be a definite "no". By running 80nsec. DRAM (VERY expensive at the time and hard to find in a 7-bit refresh flavor), replacing a few 74LS parts with HCT and trying a handful of Z80H (8Mhz. rated) chips I was able to get one of my Applicard running reliably at 10Mhz. I doubt I could repeat it if I tried. Faster than that just isn't going happen. The timing margins for dynamic memory are way too tight. 8Mhz. is a fairly standard mod, though. If anyone really wants to pursue this, let me know and I'll dig out my notes. For this, you need 100nsec. DRAM that refreshes on 7-bits. Not all of it does and not all the different part numbers even specify it one way or the other in the data sheets.
Alex's card uses a far simpler design with modern parts and static RAM. It's not out of the question that it could run at those speeds, but it's purely in the realm of experimentation.