Re: Xi 8088 - The improved version of my XT board

[Sergey <skis...@gmail.com>]

Hi Bill,

Here is the summary of the changes:
- Turbo switching circuit is modified to provide glitchless clock
switching.
- DMA uses modified CPU (4.77 MHz) clock instead of the PCLK (half of
CPU clock)
- Added selectable I/O wait state generator (from 1 to 4 wait states)
- Fixed the direction signal of X-Bus address transceiver U19 (/AEN
instead of /DMAAEN)
- Fixed the NMI enable issue (it was not wired correctly)
- Added on-board speaker (optional, external speaker can be used
instead)
- Moved flash ROM to the bottom,  closer to the ISA connector (as you
suggested).
- Added inverter on flash ROM's A16 line. So that the first 64 KiB of
ROM are mapped to BIOS space - 0F0000h-0FFFFFh, and the second 64 KiB
are mapped to the 0E0000h-0EFFFFh area (if enabled).
- Removed PS/2 / AT keyboard controller selection switches. It is
assumed that PS/2 compatible controller will be used.
- Wider power traces
- Better ground routing
- New board is 0.4" longer
- Some silk screen changes

Thanks,
Sergey

On Sep 27, 9:23 am, Bill Lewis <wrl...@gmail.com> wrote:
> Sergey,
>
> Do you have a list of what's changed and/or new on this version?
>
> I see you did move the BIOS ROM down for easier crowbar-ing out of the
> socket like we talked about.
>
> You've revamped the clock generator / Turbo selection?
>
> Bill
>
> On Monday, September 24, 2012 5:19:05 PM UTC-4, Sergey wrote in part:
>
>
>
>
>
>
>
> > I am working on improving my original XT board (http://www.malinov.com/
> > Home/sergeys-projects/sergey-s-xt<http://www.malinov.com/Home/sergeys-projects/sergey-s-xt>),
> > and it seems that I am pretty
> > close to ordering PCBs.