Tandy T100 info

[Allison]

>
>Subject: Re: Tandy T100 info
>   From: John Hogerhuis <jhoger at gmail.com>
>   Date: Mon, 16 May 2005 13:59:50 -0700
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>The basic idea is that Remem implements in CPLD a memory management
>unit dividing the 64K address space into 64 1K blocks (actually more
>than that since the option ROM is emulated). So you can map any 1K
>block from anywhere in RAM or flash into the 64K address space any way
>you like.

Ok, the usual MMU only fairly fine grained.  Does any apps make use of 
that kind of MMU and space?

>For compatibility it also emulates a 256K "Rampac" which is a vintage
>external device that hooks to the I/O bus port on a T102.

unfamiliar.

>There are multiple MMU maps selectable via an I/O instruction for
>fast-switching of virtual Model 100 environments. So for example you
>can have one map with a native Forth-in-ROM, and a couple of maps with
>the standard ROM but distinct RAM portions (the latter much like the
>"banks" in a T200 or NEC 8300 laptop)

Ok, I've done this on other systems and S100.

>Each block in the map can be marked read-only so that if you are
>emulating ROM with RAM or flash you get a perfect emulation, i.e. any
>writes against ROM don't get applied.

Handy!

Now I understand what it is and the basic logic inside.  Like many MMU 
based 8bitters the addition of large ram is usually to emulate disk.  
I'm curious to see if any actually do swaping or overlay so the app 
can access a larger space or larger data.  The reason for that is 
most cases that is rare or not even done.


Allison