Packard Bell PB450 modifications

edited November 2018 in Hardware

Yesterday, I received a package from Digi-Key with the items that I purchased on Friday:

4x 22uF 6.3V tantalum capacitors (SMD)
10x 0 Ohm resistors (too small)
2x 0 Ohm resistors (too darn small)
2x 3.3V Fixed Voltage Regulators
2x Voltage Regulator mounting kits
2x CR1220/BR1220 battery holders (one is on the board and accidentally cut the legs off since I thought it would touch the bare metal on the case, and I was wrong)
5x 128Kb 28-pin DIP 12ns cache chips (not working since the board only supports 20ns and 15ns SRAM chips).

Did the modifications on my Packard Bell PB450 motherboard (Packard Bell Pack-Mate 28 Plus), however, I didn't solder the battery holder very well and accidentally trimmed the legs off. Good news is, I bought two of them, same thing with the capacitors, fixed voltage regulators, and the VRM mounting kit. As also seen in this forum:

Voltage regulator mod (cleaned the rest of the flux off, mostly after the picture was taken):

Battery holder (will fix):


Granted my soldering isn't that great, but, it has improved, and thankfully, I still have a ton of flux left and a few wrapped up solder braid, which did get the old solder off in order for me to install the voltage regulator.

The battery holder that's installed got a lot of the flux cleaning chemical on there, so I'm going to replace it with the spare I bought and the system says the battery is dead and the one thing I wish I had was a 3.3V DX4-100 processor to make sure I got the connections set and that the voltage is spot-on and adjust the soldering if necessary.


  • Haha, lovely to see people from other forums here too :)
    Looks like we share at least 3 forums :D

  • edited November 2018

    I put the spare battery holder on last night after running errands and found out later on that the battery jumper header was missing the jumper on pins 3-4 (fortunately, I had plenty of spare jumpers), and it now keeps the settings. Got to tell you, modding this board was icing on the cake. The dual floppy drive was acting cray last night (the PC speaker was beeping erratically) as it might need lubrication or a good cleaning of the rails, but, I sent a DIR A: and DIR B: command when I booted into MS-DOS safe mode (safe.bat) with or without a diskette in the drive(s) and it did move freely and the drives were seeking without any more issues when I power cycled the desktop. Also, the L2 cache is still a mystery (will boot the drive, but, it just sits there), however, it gets detected as 128KB since the chips are 4x 32Kx8 20ns 28 pin DIP, 1x 32Kx8 15ns 28 pin DIP, and 1x 64Kx1 15ns 22 pin DIP.

  • Maybe it has problems because of the different speed grades of your cache chips.
    You calculation is ???
    4x 32k = 128k
    = 224k
    Try it with only 128k (4x32k).

  • edited November 2018

    Here's the manual for the cache installation: PB450 Cache Upgrade

    I made a mistake at the beginning: the L2 cache chips are 256Kb (32Kx8).

  • Upgraded the BIOS to the Micro Firmware 4.05.10 P4HS20 that supports the AMD processors and Cyrix (voltage regulator required), as well as the processors that has write-back cache, including the Pentium OverDrives (no interposer needed). Source thread (register to DL the BIOS):

    The only thing I need to do is run the BIOS upgrade diskette to clear the issue: CMOS battery "dead" error. Other than that, it works and I'll be surprised if my L2 cache works in the system.

  • Ran the BIOS upgrade successfully and it's not complaining about the "dead" battery. I forgot to add this string: I=e000-f2ff to the emm386.exe line in the config.sys file.

    Also, I swapped the 32x Apple CD-ROM drive (Matsushita) with the Creative Labs CR-563-B 2x CD-ROM drive for better period correctness on Friday night, read CDs without an issue, but, it wouldn't eject unless I use the manual eject method. I set it off to the side until Saturday evening for diagnostics, and when I looked at the eject mechanism motor, there was corrosion on it and the tray would barely eject (slow to eject and slow to close the tray). I ended up replacing the motor with the one I removed off of a broken CD-ROM drive that lost its laser due to a broken/shattered disk that was in there, and it's fully functional.

    Micro Firmware BIOS if anyone is interested:

  • I still haven't forgot about putting that MR-BIOS into a 128k image. It takes a few more days. I am sick and tied to my girlfriend's place with a crappy netbook without all my data. Will do it as soon as I get back home in a few days. I am curious if that will work...

  • Thanks, man. Feel better.

Sign In or Register to comment.