Upgrading HP48G


It's me again... I've found a few ram chips which have almost all the right specs I need. The problem is that they (all the 128kB x 8 types) come in 1 Mbit modules and that's the smallest I can find from non-minimum-order companies (e.g. futurlec.com or digikey.com -- digikey has a $5.00 charge for orders below $25 which I can handle)

So my question is, would there be problems if I were to use a 1Mb sram module for the initial 128kB upgrade? I wish I could post to comp.sys.hp48 but I currently do not have a news server. Anyway, any help would be truly appreciated.


Hi H.D. Can yu tell me what the par number is for the chips you have?

By typing a few (address buss) pins low on the chips you can get
the ran to operate happily as a 128 kB device.

BTW, whats the part number for the original chips, too?



I ended up buying (from Digi-key):

PT100KXCT-ND RES 100K OHM 1W 5% 2512 SMD
PT47KXCT-ND RES 47K OHM 1W 5% 2512 SMD

What I was failing to realize was that when these companies list the modules as 1 M or 1 Mb, it stands for a mega-bit, which is equivalant to 1,000,000 bits / 8 ~ 128kB. I, for an incredibly and stupidly long time, kept thinking these were 1MB (as in mega-byte) modules. Anyway, the memory was "LL" but the datasheet did say low active and low idle power; the currents were comparable to one by Sony, listed as CXK581000AM-70LL

I picked up an extra 104 SMD resistor (the 100k ohm one) to upgrade the IR receiver.

As for the original 32kB memory chip on my HP48G, it's Winbond W242575-70LL.

Also, it appears that my PCB board has a number printed on it: NI9803 (printed slightly near the center of the board). I also see another number: I34 slightly below the CPU. I am hoping someone knows something about how to place the 104 and 143 SMD resistors as according to an upgrade doc I read, their alignments vary depending upon PCB versions.

I've upgraded an HP48G before (only to 128kB user ram) but it was stolen when I was studying abroad in Hungary. I finally bought a new 48G (for $15.00!) and decided to go for port 1 and port 2. This time around, I managed to open the case without any damage whatsoever (e.g. no cutting or removing the keyboard overlay) by popping the rivets (they're not damaged and are reusable) and slowly applying pressure to the latch points. I'll document the process and have plenty of photos in case people are interested.


Hi HD.

I can't seem to find data on the ram you bought.

Also, please note that RAM can be electrically organized in a variety of ways, the most common ones being:
1 bit wide, 8 bits wide, 16 bits wide.
I have worked with 4 bit wide and 32 bit wide ram as well as the above.

Your safest bet is to get something which is pin for pin compatible and timing compatible. Don't forget voltage too, but this is pretty standard...


Edited: 20 Sept 2005, 5:39 a.m.


The ram is actually M5M51008DFP-70HIA0 (manufacturer's number). You can read the PDF here:



Just a software guy here, but 1 Mbit = 128 Kbytes, right? Is it a matter of how they are arranged behind the address decoding logic?

Also, you can post to Usenet through Google Groups. It just takes a free account.

Edited: 20 Sept 2005, 1:25 a.m.


Yes, Howard, of course. I must have been asleep. maybe HD has the right parts already...



You could always use http://groups.google.com/group/comp.sys.hp48/ for the newsgroup. You can also use Google to search the archive of the newsgroup.


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