Hey man, I'm not sure... Can't find data sheet for this IC. As long as it has all the same signals available (see many posts above) and is a DRAM chip with 262144 words of 4 bits, you should be fine. sharksym above used GM71C4400BJ70 and somehow made it work

BTW: it's fairly easy to find 44256 or 44C256 ICs. Just find an electronic junk store and look for either 286 motherboards or SVGA ISA cards from circa 1989-1992. 90% of thise cards come with 44256 or 44C256. I paid about 7$ for such card with 4 x 44C256 chips.

I'm not sure, but HY53425AS-70 seems HY534256 (256K * 4 bit)...
Any 4bit DRAM can be used
But, DIP type is better choice than SOP, SOJ type.

I had used SOJ type GM71C4400BJ70 (1M * 4 bit).
A9 pin is fixed to GND for 256K addr.

Good luck !

Thanks to all,
I will look for by Internet to download the manual of the chip, or to find another compatible like you explain!

8 chips, good for two 512kb upgrades:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4193&item=4132240478

or...

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4193&item=4132153949

I was lucky to come across an old SVGA board with [b]8[b] 4x256 dram chips! So, if you are looking for the set of chips for upgrade and can't find them locally, I'll sell a set of 4 (enough for upgrade to 512KBytes) for 5 euro or 8 US$ + shipping.

Robsy, if you are interested in this chips for your Panasonic FS A1WX, for you it'll be just shipping

Here are the pictures:

sorry for the VERRRRY late reaction

i got a broken FS-A1GT from ronnie for 35 euro..
and i fixed it somehow but that's a long time ago
still worx...

Quote:

sorry for the VERRRRY late reaction i got a broken FS-A1GT from ronnie for 35 euro.. and i fixed it somehow but that's a long time ago still worx...

Sory what this has to do with the topic?
Did you upgrade the GT to 1024kb and now it works???

lol
no, it didn't boot.. black screen..
i opened the case, pcb check.. nothing wrong with it, a few solder drops removed.. and it worx great

and i don't need 1024k.. 512k is enough..

yes and you put in a panasonic MSX2+ keyboard and it's diskdrive.

There is one strange behaviour with your GT: slot 1 does not work with many roms iirc.

doesn't matter.. but a few days ago.. something strange was going on..
slot 1 worked.. but that was only once.. i must check my gt again.

only works with some MSX1 games as i tried it when i wanted to buy him

Hm, that sounds like some addrss lines aren't properly connected. I would try to use a needle to unbend all pins that look too depressed (I did something like this with my old NES). Alternatively, just replace the whole connector

Hey dhau, I am planning to upgrade my WSX RAM to 512KB. It would be very helpful if you could fix links of photos to WSX board that was in page 2 of this topic.

Thanks

I moved all my pictures to flickr.com, and it's forum's policy not to allow people to edit their older messages. So sorry, can't help you there. Try this, may be it'll help you:

members.chello.nl/h.otten/new/msxa1wsxmemory.pdf

To tell the truth, I think this pdf is even better than this forum topic

Is it yours? I am thinking about translating it to portuguese and put it somewhere to be downloaded (MSXPro, maybe).

Thanks