Well since the A* signal was apparently originally intended by Kyoceria to control external RAM in some external interface (like the Video / Disk expansion) that Radio Shack never bought into, it wouldn't surprise me that there is some basic stub code in the "O/S" that controls it. That signal also goes to the LCD controller. The A* signal was deleted from the T102 expansion bus connector.
I also believe that PG Designs used it in their "piggy back" ROM/RAM expansion module for the M100. Regards, Peter On Thu, Apr 21, 2022 at 1:50 PM <[email protected]> wrote: > > ------------------------------ > > Message: 2 > Date: Wed, 20 Apr 2022 18:44:27 -0400 > From: Stephen Adolph <[email protected]> > To: "[email protected]" <[email protected]> > Subject: Re: [M100] 5MHz and RAM in M100/T102 > Message-ID: > < > camcmnv6afm0q9f2uabrrumntnioumy5-3ocapocpf02vu5g...@mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > Follow up: > Great news! I had an old guy eureka moment! > > So, 5MHz on T102 is pretty well baked and optimized, but an easy upgrade > for M100 was eluding me. > The main issue: > The internal stock SRAM is slowed down by the A* signal, which drives the > chip selects from signals /RD and /WR late in the machine cycle. > This leaves little time for the SRAM to react. > > The eureka ... pull A* high. > This frees up the chip selects to be driven solely by IO/M and address > lines, which opens up the timing window substantially! > > So, the M100 5MHz upgrade just got a whole lot easier. The stock SRAM > works at 5MHz by making this one change. > > <snip> > > ..Steve > >
