Panasonic FS-A1F and 128kb RAM upgrade

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By Retrofan

Paragon (1329)

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25-09-2022, 18:43

@sdsnatcher73 my idea: maybe you can create a ramdisk (with command RAMDISK 4064) in DOS2 which will use all available RAM segments including the internal RAM. Put as many files from directory 1 on the ramdisk from an SD card so the complete ramdisk is nearly used. When completed, move those files back again to another directory (number 2) and compare both directories if the files inside it are the same using a hex editor. If those files are the same, DOS2 does handle the RAM segments in the correct way I guess. And I assume it will be okay as TESTMAP doesn't fail on DOS2 as it does the memory management.

But maybe it can be done easier Big smile

By Retrofan

Paragon (1329)

Retrofan's picture

25-09-2022, 19:51

Wierzbowsky wrote:

Nice find, guys! I knew there was something wrong with that machine. But there's no datasheet for the NEC's ULA, so there's no way to configure it to get rid of the problem...

I don't know if this is something useful, the pin lay-out of the NEC uPD65013GF375, but I found it on the internet. Scroll down until you see the picture of the chip. Looks like some Japanese Wiki page.

By sdsnatcher73

Prophet (3660)

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25-09-2022, 21:44

We already know DOS2 does something and actually as TESTMAP is not doing anything different it must be that the RAM now rolls over like on other machine (so on a 128kB machine segment 8 is actually segment 0). Has to be almost, but why???

By gdx

Enlighted (5820)

gdx's picture

26-09-2022, 02:12

Several people have made an upgrade to 512kB and more without report this issue. So I think this issue can be removed.

* 4096kB upgrade. (Japanase)
* 512kB upgrade. (Japanase)
* 512kB upgrade. (Spanish)

By sdsnatcher73

Prophet (3660)

sdsnatcher73's picture

26-09-2022, 07:44

This issue only shows under very specific software. For instance the Japanese MEMTEST that is used in the first upgrade works fine on the A1F with 64kB or 128kB. It seems mainly European software has issues with ROM segments in RAM mapper. Most probable is that no European MSX2 had similar setup and developers assumed it was the same on all machines with mappers (which is clearly not true).

Still most likely the 512kB and 4096kB upgrades ensure no ROM segments will be presented and European software will correctly identify the mapper size.

By gdx

Enlighted (5820)

gdx's picture

26-09-2022, 09:43

I well meant that is likely that the memory upgrades cover the ROM segments.

This is a hardware design flaw, and this MSX was only sold in Japan. It is therefore normal that European software has not designed its software to avoid this problem. Even MEMTEST that is a japanese software does not avoid it.

By mars2000you

Enlighted (6346)

mars2000you's picture

26-09-2022, 11:31

Retrofan wrote:
Wierzbowsky wrote:

Nice find, guys! I knew there was something wrong with that machine. But there's no datasheet for the NEC's ULA, so there's no way to configure it to get rid of the problem...

I don't know if this is something useful, the pin lay-out of the NEC uPD65013GF375, but I found it on the internet. Scroll down until you see the picture of the chip. Looks like some Japanese Wiki page.

This page mentions that this NEC gate array is also used on the Toshiba FS-TM1 based on the Panasonic FS-A1. There is also a gate array on some Panasonic FS-A1 (version 3 of PCB), but apparently it's not a NEC chip.

Similar issues on these machines?

By sdsnatcher73

Prophet (3660)

sdsnatcher73's picture

26-09-2022, 14:11

FS-TM1 very likely. FS-A1 does not have a mapper (maybe it’s there in the engine but it’s not in use).

By Wierzbowsky

Guardian (3526)

Wierzbowsky's picture

26-09-2022, 17:47

Retrofan wrote:
Wierzbowsky wrote:

Nice find, guys! I knew there was something wrong with that machine. But there's no datasheet for the NEC's ULA, so there's no way to configure it to get rid of the problem...

I don't know if this is something useful, the pin lay-out of the NEC uPD65013GF375, but I found it on the internet. Scroll down until you see the picture of the chip. Looks like some Japanese Wiki page.

Thanks! Sadly, I could not find anything useful for our case there. But for the possible repairs this information may be quite useful.

By Retrofan

Paragon (1329)

Retrofan's picture

26-09-2022, 20:28

You're welcome ;-)

Just for fun: MemMan does detect the 128kB RAM correctly and is able to use it with filecopier BK under DOS1 including VRAM. MemMan was made in The Netherlands in the 90's.

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