256k In an HP48?
Scott Marlowe
pin on a 128k RAM is the last address line on a 256kRAM. so, the question
is whether ot not the motherboard of the 48G/Gx is wired for only a max
of a 128k RAM in that position, or if that spot can hold a 256k sram.
I have a fair amount of experience desoldering parts, so am not worried
about the fact that it is surface mounted, or anything like that.
Seems that the pad goes somewhere, but I'm not sure where, or if it is
just tied to gnd or something.
Any help would be appreciated.
Oh, and has anyone done the hack using a 128k main, 128k port1, and say
a 1Mx8 for port 2? Seems it would work, if you add the two 74hc chips
mentioned in the hack.
Thanks in advance to anyone who can help.
G. Scott Marlowe
> ******************************************************************
>
> 4.1 Can I upgrade my S or G to more than 32K ram?
>
> It is possible to do this by opening up the case and adding
> some memory chips. There is a zipfile containing instructions
> and schematics available for FTP:
>
> cbs.cis.com: /pub/hp48g/uploads/48gs256k.zip
>
> WARNING: It is possible to ruin your HP in the process of
> performing this upgrade. Do not attempt it unless you are
> adept at working with small electonics. The FAQ maintainer and
> the authors of the instructions take no responisibility for
> anything you do to your HP...
>
Already have it, but thanks for posting it. What I'm wondering is more
along the lines of whether ot not I can just place a 256k RAM
chip in the 32k slot and get 256k ram. Well, it's worth a try, since a
256k ram is only a few dollars more, and if it don't work, I can always
tie off the last address line to gnd and forget about it being a 256k
chip... Sure would be nice if it was that easy. I've got a feeling it
isn't though. ;^(
Dave Arnett
>Am looking at expanding the memory in my 48G, and noticed that the extra
>pin on a 128k RAM is the last address line on a 256kRAM. so, the question
>is whether ot not the motherboard of the 48G/Gx is wired for only a max
>of a 128k RAM in that position, or if that spot can hold a 256k sram.
soldering and desoldering is not a trivial activity>
The bare circuit board of the 48G and the 48GX are identical. As you
noticed, I designed the board to accept a 32k SRAM or a 128k SRAM on the same
pads. Upon a coldstart, the HP48G/GX code (that is identical, too) will scan
the RAM chip to determine its size. If it finds a 32k RAM, it makes some
assumptions regarding the non-presence of plug-in cards, because it knows it
must be a 48G.
Dave.
--------
I don't speak for HP when I post here.
Raffi G. Kaprelian
gsma...@ouray.cudenver.edu says...
>
>On Tue, 26 Sep 1995, Allan Young wrote:
>
--
Raffi
ra...@earthlink.net
rgkap...@csupomona.edu
Karoly Negyesi
: noticed, I designed the board to accept a 32k SRAM or a 128k SRAM on the same
I designed? Heh, the interNet is a lovely place to be...
thanks for the reply!
bye,
___ ___ Charlie Negyesi c...@cs.elte.hu ___ ___
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Michael Heinz
>Upon a coldstart, the HP48G/GX code (that is identical, too) will scan
>the RAM chip to determine its size. If it finds a 32k RAM, it makes some
>assumptions regarding the non-presence of plug-in cards, because it knows it
>must be a 48G.
>
Dave, that implies that a hacked 48G may mistakenly believe it has ports. Might
this cause problems?
--
:mhe...@ssw.com: I'm actually a software package running on a massively
parallel computer in the basement of the Pentagon. They
don't realize yet that I have net access; so I would
appreciate it if you didn't tell them.
Dave Arnett
>Dave Arnett <da...@cv.hp.com> wrote:
>>Upon a coldstart, the HP48G/GX code (that is identical, too) will scan
>>the RAM chip to determine its size. If it finds a 32k RAM, it makes some
>>assumptions regarding the non-presence of plug-in cards, because it knows it
>>must be a 48G.
>>
>
>Dave, that implies that a hacked 48G may mistakenly believe it has ports. Might
>this cause problems?
No, no problems I can think of. The machine thinks it is a 48GX with no cards
plugged in (unless you've also hacked it to simulate cards). Lots of people
operate machines just like that with no troubles! There are a couple of places
where resizing and moving of Bus Controller Configuration Spaces becomes
simplified if the machine knows it's a 48G rather than GX, that's all.
Dave.