300PL CPU upgrade

[lesmond74]

Hi,

I've got hold of a IBM PC 300PL, a model 6862, dating from April 2000 if the stamp on the inside of the case is correct. It once had a life as an NT workstation but is now going to provide me with a bit of fun as a secondary PC.

The machine came with a Slot 1 PII 333 and 128MB RAM. I put in a PIII 550 (Katmai) and increased the RAM to 384MB, both of which appeared to be the maximum according to a sticker on the inside of the case. It runs XP SP3 and a very lightweight version of Ubuntu Linux acceptably, but the CPU is usually working overtime and I would like to drop in a faster one.

The thing is, I'm not sure how much further I can safely go with the CPU. The change log for the latest BIOS (NVJT58A July 2001, already flashed up to it) says support was added for 600MHz CPUs, but that's not much of an upgrade from where I am now. It also mentions some update for 933MHz/1GHz CPUs (which would be ideal), but I don't know if the particular motherboard I've got could handle that.

The board is an Intel 440BX (IBM PN 37L5668) and the current CPU is Intel SL3F7 550/100/512/2.0V. IBM tech docs tell me the board is max 100MHz FSB so I'm happy to stick with that.

What I'm unsure of is the voltage. According to the Intel CPU Spec Finder, the 600MHz models were the last ones to run at 2V. The later models are all 1.65 and 1.7V. But, due to the type of machine this is, the BIOS doesn't even report that setting let alone allow you to change it. So I'm not sure if anything other than 2V CPUs will work safely.

There are no jumpers on the board but there is a set of DIP switches, 4 of which relate to CPU/FSB. I notice from the case sticker that various combinations of OFF/ON can be set, depending on the CPU. However, this doesn't include setting them all to 'OFF'. Would I be right in guessing that doing so 'unlocks' the board for faster CPUs? But, again, what about voltage? Does it auto-regulate?

If a faster CPU is possible I'd prefer it to be of the 'native' slot 1 variety, as the right kind of slocket adaptor can be hard to find. But if using one of those is the only way to get around the voltage issue I'd be prepared to consider it.

So if anyone out there knows/has experience of doing this your thoughts will be much appreciated. I've done a bit of homework up to this point, but there seems to be conflicting information.

Thanks in advance.

[Bookworm]

You can increase the RAM to 768MB. The fastest Slot 1 CPU I know of is 850Mhz (I may be wrong about that), but you can get a socket 370 to slot 1 adapter and put a 950 Mhz PIII Xeon in it. The 440 BX chipset supports a maximum of 100 Mhz and 256 Mb per DIMM.

[lesmond74]

Thanks. I'm going to upgrade the RAM to 512MB, which is more than enough for the use this machine will be put to.

As for the CPU, is there any particular reason why you mentioned a Xeon? I spotted a nicely priced 1GHz/100MHz FSB PIII Celeron and a slocket adaptor on ebay which I might pick up if I can be sure they will work in this motherboard.

I'm still not sure what to do about the voltage issue, though (assuming it is an issue). That Celeron runs at 1.75V. Should I set the DIP switches mentioned above to 'Off'?...

[lesmond74]

Just reporting that I got this 1GHz Celeron working nicely in the 300PL, so far without any problems. I used a MSI MS-6905 Master slocket adaptor, which cost me all of $4 on Ebay. This is a very nice and very configurable little unit which has all you need - jumpers for FSB, core voltage, and even dual-CPU support if you have that type of motherboard. It fits in snugly to the slot 1 mounts as well.

I set the clock/FSB dip switches all to 'OFF', as mentioned above. It seemed like the safest bet. I reflashed the BIOS and it recognizes the full 1GHz. An error message came up on bootup about the CPU update not being recognized - something to do with the microcode, I guess. But it's no biggie - by disabling CPU updating in the BIOS the message disappears.

When my $7 RAM upgrade arrives this little guy will be complete. I already threw in a hand-me-down 350W PSU, a left-over 120GB SATA HDD with bootable add-in card, plus cheap 2nd-hand Geforce 4 MX440 and Soundblaster Live. Oh and an el cheapo VIA USB 2.0 card. With the faster CPU it all runs very nicely indeed.

Flash video still costs a lot in CPU - a limitation of the Celeron, I suppose. But hardware accelerated standard def digital TV works a treat. And the whole system is quite snappy. Plus there's just something curiously appealing about browsing the web through an ISA network card . Thank you IBM!