Sony HB F1 XV MSX2+ to 128KB?

By grit

Resident (53)

grit's picture

21-02-2008, 10:24

Hello all,

I'm trying to find a way to get 128KB in my Sony HB F1XV. The idea is to put an extra 64KB parallel to the main memory already available, disconnect the the pin 16 of the new IC's and connect it to /CS2 on the MSX Engine (pin 45). Sort of the same mod as on the NMS8220 as described here:

But this would seem too easy hm? ... Also, I don't have a datasheet of the machine and there is another IC which seems to handle memory too, it's the 'Sony MB670836' (a square block resembling the MSX engine) Googling displays no results on this IC, any ideas what this thing does?


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By Jipe

Paragon (1560)

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21-02-2008, 18:05

if your Sony have a mapper inside you can upgrade memory else buy a expand memory cartridge

By sd_snatcher

Prophet (3557)

sd_snatcher's picture

23-06-2010, 00:47

Here's a guide to upgrade your Sony to 256KB (in Portuguese, use google to translate).

I wonder if it's possible to use the mini-mapper 1MB upgrade board on those Sony MSX2+ to upgrade it to 1MB.

By RetroTechie

Paragon (1563)

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23-06-2010, 11:34

I'm afraid I'm not familiar with this particular model... What type of MSX engine IC does it have inside? S1985? T9769?
Does it have any empty ROM sockets? (which might be used to place an SRAM without soldering on top of other ROM)

pic of the mainboard would help...

By Leo

Paragon (1236)

Leo's picture

23-06-2010, 14:51

i believe all msx2+ have mappers.
T9769 is only in panasonics , i think because they are the only to have turbo 5.3MHz.
there is a good chance that s1985 is used .

By sd_snatcher

Prophet (3557)

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23-06-2010, 22:53


This thread has pictures of the board. It doesn't have any empty ROM sockets, unfortunately. It has the S1985 MSX engine, but its mapper pins aren't connected. The mapper is implemented on another chipset on the board: the Sony MB670836, as the B@ss Home page article describes.

Yes, that's true. All native MSX2+ have mappers, because it was required by the specs. Unfortunately, all of them also have only 64KB of RAM.

The Sanyo MSX2+ models also have the T9769, but they doesn't seem to have the turbo circuitry. Maybe it's possible to upgrade their mobos to have this feature.

By RetroTechie

Paragon (1563)

RetroTechie's picture

24-06-2010, 00:13

I have a japanese Sony MSX2 (HB-F1 II) that also has a (different) custom IC besides the S1985. AFAIK it serves as address multiplexer for the DRAMs, and has the speed control / pause circuitry. I'd guess this MB670836 is something similar but with MSX2+ extra's. But you'd have to research pin connections to know for sure.

Probably easiest would be to remove the DRAMs, solder a 512K x 8 bit SRAM on top of one of the ROMs, and connect the upper address bits to expanded (mapper) address lines from S1985 (and suitably wire control signals). I suspect that might be possible with wiring alone, but perhaps some logic chip(s?) would need to be added. Anyway: there doesn't seem to be a ready-made / tested description online for that... Eek!

By sd_snatcher

Prophet (3557)

sd_snatcher's picture

22-04-2011, 00:31

The article on expanding the HB-F1XDJ and HB-F1XV internal memory was moved here.