ancientelectronics

The IBM PC 350 was released in the mid 1990’s as an office / home desktop PC. It came in several sub models that used completely different motherboards and CPU’s from a socket 3 486 class up to socket 7 Pentiums all using the same case. In this article were going to look at the sub model 6587 which is the last sub model in the PC 350 class.

The case for the PC 350 is both sturdy but at the same time not extremely heavy. On the front there are LED lights for HDD activity and a power LED next to the large white power button. There is no reset button.

One pretty cool feature is the sliding front cover that slides to the left revealing your various drive bays. There is room for two 5 1/4 inch drives as well as a 3 1/2 bay and two internal 3 1/2 bays for hard drives. In the upper left corner is a cut out for an optional PCMCIA interface which I’ve never seen on a desktop before. Unfortunately mine did not come with this option installed.

My PC 350 did come with an 850MB hard hard drive installed which sounds about right for the time. A CD-ROM drive was an option but mine did not come with one installed. Installing a 5 1/4 drive can be a little taxing and removing the bay bezels can require a lot of force or completely removing the metal drive holders inside which also is not easy due to the assembly being held in by a hard plastic screw.

On the back we have from left to right, a infrared port for connecting an infrared receiver for wireless inferred communication with compatible devices. Next we have two PS/2 ports for keyboard and mouse followed by a serial port, two USB 1.0 ports and a parallel port. Lastly there is a VGA port for the built in video.

There are no screws holding the upper case on and accessing the motherboard is achieved by depressing the plastic tab in the upper left corner of the case and pulling back and then up on the upper case. Thankfully this tab is made from pretty rugged and thick plastic and feels fairly resistant to breaking off.

On the underside of the case is a simple chart explaining the memory configurations as well as a basic motherboard layout and the various switch settings. I always like when PC’s do this as it helps greatly when making basic changes like CPU upgrades.

Here is a view of the drive bay assembly removed from the case as well as the hard plastic screw that needs to be removed to get the metal assembly out.

Now lets take a look at the motherboard and relevant parts.

The PC 350 motherboard does use a standard lithium battery to store CMOS settings. In the image below is is obscured by the IDE cable.

1) CPU – My model 6587 came with a Pentium 133 but is easily upgradable. The chart found on the case underside gives settings for installing up to a Pentium 166 but online sources indicate a Pentium 200MHz classic or even a 166 or 233MHz MMX chip can be successfully installed though you may need to experiment with motherboard switch settings (Wikipedia suggests the 75MHz setting should work for 233MHz).

The MMX chips take a lower voltage from what it appears the board can provide so use caution if your going to attempt an MMX install. For a Pentium 200 classic the jumper settings were not present on my jumper sheet but through trial and error I found the settings for the Pentium 120 allowed for 200MHz operation with the P200.

The CPU’s on all of these machines are fanless and only come equipped with a passive cooling heatsink, though a rather tall one.

The instructions and all paperwork only refer to 3.3 volt Intel Pentiums CPU’s being compatible with some sources claiming Cyrix and AMD chips to be incompatible though I was able to upgrade my board with an IBM branded Cyrix 6×86 PR 166+ CPU without issue. I just made sure my CPU was labeled as requiring 3.3 volts (most Cyrix 6×86 CPU’s seem to require only 2.9 volts).

*Correction* The above chart refers to the Cyrix / IBM CPU as a “PR 166+” as it should be labeled as a P166+

2) RAM – The PC 350 has one 168 pin RAM socket as well as four 72 pin RAM sockets for memory expansion. You can expand the memory up to a total of 192MB and the convenient chart found on the underside of the case lid has a graph showing the advised memory configuration for the desired memory amount.

My PC 350 came with 32MB of memory installed via one 16MB 168 pin stick and two 8MB 72 pin sticks. I originally thought I would try using a single 32MB or 64MB stick of 168 pin memory and forgo the 72 pin sticks but none of my 168MB sticks would physically fit the 168 pin slot. I tried several sticks and they all were physically very slightly off and would not install. This is because I later discovered the 168 pin slot is keyed for 5 volt SDRAM which is not compatible with the 3.3V (the common used SDRAM).

3) L2 cache slot – L2 cache on the model 6587 is via a COASt module fount next to the CPU and can accept either 256KB or 512KB of L2 cache. Mine came with a 256KB stick though I needed to remove it and clean the contacts before it was recognized.

4) Video – The PC 350 comes with a S3 Trio64V+ chip on the board along with the ability to expand the memory from 1MB up to 2MB. The Trio chipset is an extremely DOS compatible chip proving excellent 2D support and compatibility for DOS and Windows 9x.

5) Riser card – The PC 350 uses a riser card in order to provide both PCI and 16-bit ISA expansion slots. In total the riser provides three PCI and five ISA slots though three slots are shared PCI/ISA slots and two are dedicated ISA slots. The opposite side of the riser provides for one of the stand alone ISA slots as well as a connection for power.

6) Floppy/IDE -The 350 motherboard provides for standard floppy connection as well as two built in ATA-2 IDE connectors for a total of four IDE compatible devices.

7) Switch – This is the switch used mainly for selecting your processor speed. Thankfully the chart on the underside of the case provides the settings and switch configurations should you decide to change CPU’s. The chart provided does come off as a little confusing though as It does not list actual FSB settings or provide a setting for 200/233mhz CPU’s. The Wikipedia entry on the PC 350 advises setting the switches to the “75 MHz setting” for a 233MHz Pentium.

8) PSU – The 350 motherboard requires three PSU connections to the board. Besides the standard AT connection the 350 also requires an additional AUX connection as seen below.

The IBM PC 350 makes a fair retro computer. It excels at DOS retro gaming and needs very little besides an ISA sound card to have a very compatible machine. As a Windows PC it is quite acceptable and a PCI 3D accelerator card such as a Voodoo would do wonders. The BIOS tends to be fussy though and when I made ANY changes including simply unplugging the mouse the machine demanded I enter the setup feature upon restarting and change/save the new settings. There are other annoyances such as the extra connection needed on the power supply as well as the slightly picky 168 pin RAM slot.

The case itself is quite nice offering a sturdy design, decent bay expansion as well as being easy to get into. I also like the sliding piece on the front so you can cover up your ugly discolored drives when not in use. Adding drives though requires some disassembly and is a hassle.

For a DOS PC the IBM PC 350 will serve you well though for Windows it’s passable but there are much better options. As a side note I could not get Windows 95 or 98 to install on my machine. This was due to some sort of driver conflict at the Windows splash screen I was never able to resolve. The machine IS Windows capable however and this problem boiled down to my particular machine.