RAM problem

[Martymcfly]

So I have an Expert system which is supposed to have 2 MB of RAM.  It currently will not boot 2 MB games, only 1 MB games and gives me varying messages every time I attempt to boot a 2 MB.  I think the problem may be the SRAM/battery issue with the system now defaulting to only 1 MB of ram.  I would like to run the Switch.x program to update the bios, but I'm not sure how to do this as I don't have any of the system disks.  So I have a couple of questions:

What's the best way to go about running the switch.x program or obtaining system disks to do so?

Where is the SRAM battery and how do I change it after I change the settings in switch?

Thanks!

[lydux]

Hi,

Are you able to give us some of these messages when loading a 2MB game ?
Because I see no point why you could have the sram set to 1MB unless someone have done it manually. Hope I'm wrong, but you could have a faulty RAM chip on upper 1MB bank.

What's the best way to go about running the switch.x program or obtaining system disks to do so?

Well... The best way is to do it yourself if you have a working 5' drive on your pc. So you could write an human68k image on a blank disk.
You can also ask someone for a copy of this disk ! Where do you live ? Maybe an user here can help you.
As alternatives, I have others (but harder) tricks to get a bootable disk which request a keyboard, and a way to connect your x68k to your pc using the RS232 line (so you need a DB25 null modem cable).

Where is the SRAM battery and how do I change it after I change the settings in switch?

The battery is here to keep the sram data alive while the main psu is unplugged. You will find it on the IO board, which is in the "foot" of your x68k. You don't necessary need to remove it to clear to sram but we strongly encourage you do change it ! Old batteries tend to leak acids that could destroy the pcb.
Just disconnect the main power source and open the right side of your x68k, you should see a ribbon cable coming from the main board to the IO board. Gently unplug it from the IO board, and wait for about a minute, the sram will loose its content and will be rewritted to factory default on next boot.

Good luck !

[BlueBMW]

Expert systems will default to 1mb ram when the sram is cleared (from dead battery or otherwise)

Your easiest bet is to have someone copy you a human68k disk.  Have you got a keyboard?

[lydux]

Expert systems will default to 1mb ram when the sram is cleared (from dead battery or otherwise)

Oh ! Didn't know that. Thanks !
So yeah, that's the problem.

[Martymcfly]

Thanks for the replies!

I do have a keyboard. Would anyone be willing to copy me a human68k disk and mail it to me? Id pay for the disk, shipping, and effort obviously.

[BlueBMW]

Shoot me a PM with your address and Ill mail one out to you,

[Martymcfly]

Thanks guys, i found someone to send me one. Once i change the settings in switch, i assume it will continue to reset itself back to 1mb everytime turn off the computer until i change the battery, is this correct? And is there anything else i need to reset besides the ram setting?

[lydux]

Well, not exactly.

Basically, there is a power switching circuitry for the sram :
- if the main PSU is plugged, it will use it (even computer off). This is will also charge the battery at same time on earlier models (Ni-cd type batteries).
- if the main PSU became unplugged, it will switch to the battery.

So, if you have never changed your battery, you really should take a look at it.

And you normally don't need to change anything else in SWITCH.X.
It seems this 1MB default setting is really specific to Expert models. All others have default settings in accordance to their hardware.

[BlueBMW]

Correct.  If you leave the system plugged in with the main power switch on the back turned on, your sram settings will hold.  As long as your red light is on, you should be ok.

[lydux]

Just want to know BlueBMW : what kind of battery equip Expert models ?

[BlueBMW]

Experts have coin cell type batteries.  I usually solder on a holder and use cr2032 batteries.

[caius]

Just want to know BlueBMW : what kind of battery equip Expert models ?

Hi Master,
Expert models use 3Volt lithium cell CR2450 from Sony, see attached pictures.
They are widely used in japanese computer, I found these also on FM-TOWNS.Obviously, electrically  they can be replaced by more common CR2032  - though CR2450 is designed for devices that require high current (3.0 mA) -  but keep in mind that dimensions are different , CR2450 has larger diameter so they won't fit in a CR2032 battery holder without some modifications!

[BlueBMW]

Correct, a CR2450 is a more correct replacement.  CR2032s are sometimes easier to find.  I havent had issues in using them, but I suspect they may not last as long.