Old HP48SX resurection and upgrade

[Claudio L.]

(02-16-2019 07:38 PM)manjo Wrote:  Hello all,
I had an old 48SX (revE) in a drawer for a long time.
when cleaning my drawers I found 128k*8 SRAM low power chips
in one of my other drawers, so...

For fun I thought to upgrade it to 128k.
Upgrade went fine, desoldered the built in 32k very clean an nicely

I put in 128k top 4 pins remained without pads (unconected)
bridged Vcc pin to CE2 (this is VCC) and routed A15 and A16 to
pins 18 and 19 on expansion connector (A15 and A16 respectively)

Everything works fine, only... MEM still reports 30k :-(

Is IRAM fixed size in ROM on 48SX (revE)?
Is it not A15 and A16 pins 18 and 19 on SX?
Other Thoughts ideas ?

Welcome back!
I have no idea if it's fixed in ROM but if you connected the address lines, it should be visible to the CPU, my first instinct would be to try some peek and poke from Saturn assembly to see if the RAM is there or not.