HP48SX IRAM upgrade

[Mario Lohajner]

Hello all,

-just recently I found my old 48SX in a drawer, I remembered I purchased
128k x 8 Low power chips long ago, so... for fun more than anything else
I thought to upgrade the internal RAM to 128k.

Removed the factory 32k chip and squeezed the 128k very neatly, routed
A15 and A16 lines to expansion port pins 18 and 19.

Memory chip seams to be working fine -the problem I have is that 48SX
still reports 32k.

Has anyone tried similar thing with SX?
(G doesn't count since G is practically all ready for it)
Is there a reason why 48SX (rev.E) would not be able to count/detect and
use 128k as IRAM ?

Thughts, ideas, suggestions... all wellcome :-)
Mario Lohajner
manjo

[Craig Ruff]

The 48SX ROM may not expect to ever see additional RAM in the internal RAM
area. It was common for people to upgrade the 48G/GX with additional RAM.
I don't recall if the memory controller was different between the two
models, but that could an issue.

[Mario Lohajner]

Thank you for a fast response,
yes as it seams..
SX doesn't expect to see additional RAM, AND it get's overlayed
(address-wize) with PORT1 :-( so...

IRAM upgrade on 32 kB 48SX -is NO GO :-(
SX is in many ways inferior to G/GX anyway so...

It was a fun mini-project and I was proud to see how nicely and neatly I
did it so ... to bad it didn't work as expected :-)

Since SX is still open I might re-work the entire thing to 32 kB IRAM
and 128 kB as PORT1

regards,
Mario Lohajner
manjo

[Hic quondam locutus sum]

Post by Mario Lohajner
Thank you for a fast response,
yes as it seams..
SX doesn't expect to see additional RAM, AND it get's overlayed
(address-wize) with PORT1 :-( so...
IRAM upgrade on 32 kB 48SX -is NO GO :-(
SX is in many ways inferior to G/GX anyway so...
It was a fun mini-project and I was proud to see how nicely and neatly I
did it so ... to bad it didn't work as expected :-)
Since SX is still open I might re-work the entire thing to 32 kB IRAM
and 128 kB as PORT1
regards,
Mario Lohajner
manjo

I've never owned an HP48SX ( I only have GXs ), but, isn't it possible to merge
both port 1 and port 2 with IRAM on the SX?

Regards,

Hic quondam locutus sum

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[Mario Lohajner]

Post by Hic quondam locutus sum
I've never owned an HP48SX ( I only have GXs ), but, isn't it possible to merge
both port 1 and port 2 with IRAM on the SX?
Regards,
Hic quondam locutus sum
--------------------------------------------------------------------------------
Send e-mails to "NOhp48 Sat Palephnaught Adot Morg"
( Remove the capitalized letters spelling "NOSPAM" )

Yes it is possible and I did merge port2 with iram, but...

My primary goal was to replace the IRAM (built-in 32 kB) with 128 kB so
it would be 128k IRAM.
This "works" as well, but due to the memory map in 48-SX, memory past
32k is not available in "normal / standard" operation.

Maybe i could unconfigure the #80000 (port0) and get access to
overlapping part of 128 k but, it would not be normal and possibly only
specific user programs could use this area.

BUT since 48-SX is outdated and obsolete, and due to known issue of
ON-key not working without additional pressure under the screen which is
getting worse I decided not to mess with SX anymore.

I stored / archived the SX for "historical" purposes and continue to use
the 50G (my absolute favorite so far)

Mario Lohajner
manjo

[Hic quondam locutus sum]

Post by Mario Lohajner

Post by Hic quondam locutus sum
I've never owned an HP48SX ( I only have GXs ), but, isn't it possible to merge
both port 1 and port 2 with IRAM on the SX?
Regards,
Hic quondam locutus sum
--------------------------------------------------------------------------------
Send e-mails to "NOhp48 Sat Palephnaught Adot Morg"
( Remove the capitalized letters spelling "NOSPAM" )

Yes it is possible and I did merge port2 with iram, but...
My primary goal was to replace the IRAM (built-in 32 kB) with 128 kB so
it would be 128k IRAM.
This "works" as well, but due to the memory map in 48-SX, memory past
32k is not available in "normal / standard" operation.
Maybe i could unconfigure the #80000 (port0) and get access to
overlapping part of 128 k but, it would not be normal and possibly only
specific user programs could use this area.
BUT since 48-SX is outdated and obsolete, and due to known issue of
ON-key not working without additional pressure under the screen which is
getting worse I decided not to mess with SX anymore.
I stored / archived the SX for "historical" purposes and continue to use
the 50G (my absolute favorite so far)
Mario Lohajner
manjo

Sorry for the belated reply. AFAIK the HP48S/SX is hard coded in the ROM to only
work with 32KiB of IRAM. There's no real way to change it without modifying the
ROM. The IRAM memory controller supports up to 512KiB connected to it, but,
during the device initialization on the calc the IRAM memory controller's
address space will be changed to 32KiB regardless of what is actually connected
to it. Also, note that IRAM can be located at any integer multiple of 32KiB in
the HP48S/SX's address space, except for #00000. The location of IRAM is stored
in the MMIO register called "IRAM@" so that the OS can use the RAM when the
upper 32KiB of ROM is uncovered.

Regards,

Hic quondam locutus sum

--------------------------------------------------------------------------------

Send e-mails to "NOhp48 Sat Palephnaught Adot Morg"

( Remove the capitalized letters spelling "NOSPAM" )

[Mario Lohajner]

Thank you for a fast response,
yes as it seams..
SX doesn't expect to see additional RAM, AND it get's overlayed
(address-wize) with PORT1 :-( so...

IRAM upgrade on 32 kB 48SX -is NO GO :-(
SX is in many ways inferior to G/GX anyway so...

It was a fun mini-project and I was proud to see how nicely and neatly I
did it so ... to bad it didn't work as expected :-)

Since SX is still open I might re-work the entire thing to 32 kB IRAM
and 128 kB as PORT1

regards,
Mario Lohajner
manjo