Toshiba HX-10S memory upgrade?

Resident (59)

15-02-2020, 01:57

Having recently peeked inside my Toshiba HX-10S I wondered how difficult/easy an upgrade to the d version (16 kb to 64 kb ram) would be.

After a quick comparison of the two,
the S: https://www.msx.org/wiki/images/thumb/b/bb/DSCS6954.JPG/228p...
the D: https://www.msx.org/wiki/images/thumb/3/32/Hx10d10.jpg/230px...

I noticed only two differences, (apart from the memory chips, of course) on the board (D version, highlighted capacitor and resistor are missing on the S): https://photos.smugmug.com/photos/i-mV9rNcH/0/bf0cb07d/M/i-m...

Could it really be as simple as adding a resistor and a capacitor and replacing the appropriate memory chips? Since my soldering skills are restricted to snes cartridge battery replacements and the system is doing fine with a memory expansion cartridge, I am unlikely to try this, but I'd be interested to know ^_^

By gdx

Enlighted (6215)

15-02-2020, 09:28

If you replace the ICs 416 (IC6-IC13) by 4164 and replace the two straps 16K by the resistor 64k, I think you will get a HX-10D.
About the chimical capacitor, it's better to added the sames as other capacitors at C12-C15 locations. (104 = 100 nF)
If you want try this upgrade, use sockets!

By Wild_Penguin

Hero (644)

15-02-2020, 13:08

I wouldn't be too fast with this upgrade. Meticulously check the MB for other differences and measure the voltages and compare the datasheets of the chips in question.

I've noticed at least a few differences in the pictures you didn't: the jumpers near the bottom and right edge are differently set up for the 16kb and 64kb machine. It might be so trivial you just forgot to mention it, and it maybe this is the only difference! Did you notice the 64k x 1 chips have voltages shuffled around compared to the 16k x 1 chips? Maybe the jumpers are enough for the differences (V_dd, V_bb, V_cc and A7 -> at least 4 jumpers in total should exist (to accomodate these differences) and be set accordingly on the MB!).

Better measure than be sorry afterwards!

By Emphy

Resident (59)

15-02-2020, 14:02

Heh, thanks for being polite about it, I definitely agree not start soldering on that board.

There's J1,J2,J3,J5 marked with 16kb - 64kb, so that would account for what you said. J4 is marked JIS - A1U, whut?

By gdx

Enlighted (6215)

15-02-2020, 14:38

Emphy, can you tell us which slot is the RAM, slot 0 or slot 2?
If the RAM is not in slot 2 then there are probably other straps to move the RAM to the slot 2.

By Emphy

Resident (59)

16-02-2020, 01:28

gdx, a bit of a problem trying to determine this: I am using testram via the megaflashrom 512kb. It is detecting the cart's memory as main ram (64kb in slot 1.0 when using rom, slot 1.2 when using com) and not seeing the on-board memory at all. I tried disabling the memory in the cart's recovery mode, but this changes nothing in testram.

By gdx

Enlighted (6215)

16-02-2020, 01:51

To determine this, turn on your MSX without any cartridge inserted and enter "PRINT INP(&HA8)".
If you get 0, the RAM is in slot 0, 160 if in slot 2.

By Emphy

Resident (59)

16-02-2020, 02:02

Slot 0 it is.

By gdx

Enlighted (6215)

16-02-2020, 09:05

Thank you, I add this to the wiki.

I only noticed the following differences.

So I think you can upgrade your HX-10S by changing the 16K/64K straps, the 8 RAMs and adding the 4 capacitors of 100 nF. You will need a good desoldering pump and 8 RAM sockets. If you do not feel capable of doing it so buy the components and ask someone competent.

The resistor is sometime replaced by a trap.

If you find good RAM everything should go well.

By rderooy

Paladin (686)

16-02-2020, 10:32

@Emphy: You may have noticed on the HX-10 wiki page that your model is not dumped and emulated. Any chance you can dump the ROM's so it can be added? https://www.msx.org/forum/msx-talk/emulation/dumpingreverse-...

By Emphy

Resident (59)

16-02-2020, 14:09

I am going to leave my board as is. Apart from my lack of soldering skills, I dislike the idea of slaughtering its board for no better reason than to satisfy my curiosity (thanks to modern carts with memory included, I've yet to encounter the situation where I am missing the 64kb internal memory, even when I am in an archaic mood and load some software from tape). From what I am seeing at marketplaces and auctions, the 10s is also far less common.

On top of that, the 10d is regularly available for next to nothing, so I could always use the less destructive "swap boards" solution should I want a 64kb system in my beautiful red case

@rderooy: I'll have a looksy at the software package.