RAM issues

Take the RAM back and get a new stick.

May have to adjust memory timings (CAS-tRCD-tRP-tRAS, in the BIOS) and/or memory voltage (in the BIOS) - increasing them a bit.

Which CPU ya using? How does it run with memory frequency decreased? How does the system run with just the one twinmos module? Using latest motherboard BIOS?

I have a AMD Athlon XP 1800+. I'm not very experienced with adjusting timings etc in BIOS, so probably best to take it to a shop & get them to do it?

AMD XP1800+
2x256 DDR400
Chaintech 7NJL1
Radeon 9600XT
52x32x52 CDRW
DVD
Wacom Tablet - USB

Can't take it back, as it was bought from an online auction. It worked for a while (when I had it in slot 2) then when I moved it to slot 1 (to ensure both Memory Channels had 512MB - 1x512 in slot '0', 2x256MB in slots '1' + '2') the system started crashing. With the stable config I didn't notice any increase in performance, either.

AMD XP1800+
2x256 DDR400
Chaintech 7NJL1
Radeon 9600XT
52x32x52 CDRW
DVD
Wacom Tablet - USB

Could this problem be related to either my PSU (300W) or a lack of cooling? I bought the computer a while ago and am fairly sure it's just a standard fan etc. Sorry about my lack of specifics, but I'm not very technically skilled - a user, not a builder...

AMD XP1800+
2x256 DDR400
Chaintech 7NJL1
Radeon 9600XT
52x32x52 CDRW
DVD
Wacom Tablet - USB

Press 'delete' key upon system bootup to get into BIOS. Not sure how your BIOS is laid out. In "advanced chipset features" section, set "system performance" to "expert" in order to tweak the system. Set CAS Latency to 2.5. tRCD to 3 and tRP to 3. Set the tRAS value to 11. "DIMM voltage regulator" at 2.7V, in the "frequency/voltage control" section. Save and exit BIOS.

How does the system run with just the one twinmos module - without the two 256MB modules?

It works perfectly in this configuration?:
[256MB module]
[512MB module]
[Space]
[256MB module]

Oh crap this is embarrassing...
Turns out that the advice I read on another forum telling me to consider the 2 'side by side' slots as 'slot 1' and the separated slot as 'slot 0' was wrong. Shoulda been

512
256
{space)
256

All is running fine now...I'm off to stand in the corner...

Thanks for all your help though - I may yet have a look at the BIOS, but don't really want to tempt fate!

AMD XP1800+
2x256 DDR400
Chaintech 7NJL1
Radeon 9600XT
52x32x52 CDRW
DVD
Wacom Tablet - USB

The 2 side by side slots would be considered one channel. The seperated looking slot as the second channel. Best would be memory balanced across both channels but could just settle for the best configuration that is fully stable.

Yeah, that was my undewrstanding too, but the MoBo is laid out 1/2/space/3, rather than 1/space/2/3. I've been burning CDs and gaming on it for the whole time since my last post, with no issues whatsoever, and PC Wizard reports my RAM as being 1GB (but lists it 256/512/256?), so I think I'll leave it at that - small increase in performance & faster boot is OK, considering its a 1800+ (1537 true). I've got a Gigabyte GA-7N400 Pro 2 & AMD XP3200+ coming in a week or so anyway, so that'll be a welcome improvement. Thanks for all your help, Prof!

AMD XP1800+
2x256 DDR400
Chaintech 7NJL1
Radeon 9600XT
52x32x52 CDRW
DVD
Wacom Tablet - USB

You're welcome. Glad to help!