Upgrade MSX1 to MSX2

By skumlerud

Resident (39)

skumlerud's picture

06-03-2019, 09:25

What would it take to upgrade a MSX1 to MSX2? From what I can see the following is the minimum to run MSX2 software:

- Upgrade VDP, add 128Kb videoRAM.
- Atleast 64Kb RAM.
- MSX2 BIOS (would probably need patching).
- A floppy controller/drive and disk BIOS.

Optional:
- RTC
- Memory mapper / RAM expansion.

Am I missing something? I have a broken SVI 728 (broken case, broken keyboard, broken PSU board...) that I'd like to do something with. Yes, I know it's easier to just buy an MSX2, but I'm doing this for the challenge and not to save money.

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By Fabf

Master (222)

Fabf's picture

06-03-2019, 09:45

You probably need to add an internal expander.
I recommand the use of an EPM for expander, mapper and glue logic.

Here you can find some achievements :
http://msxvillage.fr/forum/topic.php?id=1457
http://msxvillage.fr/forum/topic.php?id=3217&pt=1

Very good challenge, have fun ! ;)

By Manuel

Ascended (15451)

Manuel's picture

06-03-2019, 10:00

Check the requirements in the MSX2 technical data book. The disk controller is not required, for instance.

By gdx

Prophet (2775)

gdx's picture

06-03-2019, 11:31

RTC is not optional even if it not necessary for games. By cons the floppy drive is. You can put an adapter to flash card instead.

By skumlerud

Resident (39)

skumlerud's picture

06-03-2019, 12:20

Fabf wrote:

You probably need to add an internal expander.

A slot expander you mean? I'll have to look closer at the innards of the 728 and see what it needs. This slot/subslot thing still confuses me Smile

Fabf wrote:

I recommand the use of an EPM for expander, mapper and glue logic.

What is an EPM?

Thanks, very interesting read!

By Nprod

Resident (35)

Nprod's picture

18-03-2019, 12:16

Check out fzanoto's MA-20 clone project, it's open source.

Thread here
Source

The cartridge uses an Altera CPLD for the glue logic and a few other ICs for things like composite out, 512kb memory mapper and MSX2 ROM. It's definitely the "cleanest" MSX2 upgrade i've seen. I'm guessing the Altera chip is what Fabf referred to as an "EPM" since the model is "EPM7128"

By Parn

Champion (353)

Parn's picture

18-03-2019, 13:45

@skumlerud: The SVI-728 doesn't have any internally expanded slots. This means it only has 4 slots available. The internal ROM occupies slot 0, while internal RAM occupies slot 1. Slot 2 corresponds to the top cartridge slot, and slot 3 is the bus expansion in the back. MSX2 usually have at least one internally expanded slot and the MSX2 SubROM (its BIOS and BASIC extensions) resides in one of those slots.

The Panasonic FS-A1F, for example, has slots 0 to 2 unexpanded (0 has the main ROM, 1 and 2 are cartridge slots), but slot 3 is internally expanded to accomodate the RAM (at slot 3-0), the SubROM (at slot 3-1) and internal software (at slots 3-2 and 3-3). This is a fairly common setup. But in your case, if you never use the expansion bus, you could put the SubROM there (at slot 3). I'm not 100% sure this would work but at least it would be simpler to do.