TR and Memory Mapper

Champion (326)

05-03-2013, 21:29

Guys, is it possible to force a TR (ST 512kb) to use an external memory mapper if it's smaller than the internal?

The reason I ask is that I used to use a 1Mbyte external MM, and force use with MEMTR, when playing certain MSX1 disk converted games as this is the only way they would work.
Now I only have a 256Kb MM and I can't get the TR to use it...

By wouter_

Master (218)

06-03-2013, 13:37

Colemu wrote:

Guys, is it possible to force a TR (ST 512kb) to use an external memory mapper if it's smaller than the internal?

A TR will _always_ select the internal memory mapper as primary mapper. Whether the size of that mapper is bigger or smaller doesn't matter. The reason for this is that (in R800 mode) the internal mapper is faster: the internal memory bus in a TR runs at 7MHz, but when accessing an external mapper it has to go over the slower 3.5MHz external memory bus.

Anyway, this is the default behavior. I don't know if it is possible to somehow 'switch' the primary mapper after the MSX has booted. I also don't know which software component is responsible for selecting the primary mapper (is it the BIOS, DOS(2), both, ...).

By Google

By Colemu

Champion (326)

06-03-2013, 18:11

I used to have no problems switching to the 1024K memory mapper by using MEMTR as this choses the largest memory mapper available (in this cast the external 1 Mbyte one)

Now my mapper is smaller than the internal, MEMTR chooses the internal mapper (as this is now the largest). I just wondered if there is a program like MEMTR that you can actually choose which mapper to use?

By Colemu

Champion (326)

10-03-2013, 12:59

OK, if there is no way to set my external memory as default, is there any other way I can get these 'problem' games to run on the Turbo-R?