Here is me story, I hope it helps.

My Dad and I worked for NCR. (Sssshhh, don't tell anyone!) Dad bought a P75, 8Mb RAM, with Windows 95 Upgrade, 1.1 GB HD, model 363TPC, with the 19.2 modem/sound card/voice mail. After awhile Dad upgraded to 16Mb of RAM.

Dad had to send the TPC board back 3 times. The 4th time it died, I bought him a 33.6 USR Sportster internal. (This is when they had the rebates out and the 56k version were just coming out.)

We removed the TPC board and installed the modem, so no sound card or Voice Mail anymore. No big deal, the soundcard did work with a lot of games, and the voice mail was a hassle.

Then Dad went out looking for a new sound card. He also looked into upgrading the processor. The manual shows it can only go to 120Mhz. It didn't seem worth the money, so he bought a new Compaq 166MMx. (This when the MMx processors were just released.)

So, I bought the Globalyst from him on the cheap. I just did without the sound card for about 6 months then I got a Turtle Beach Malibu 64 Surround. It had more features for less money than the comparable Sound Blaster. BIG mistake, I'll never buy Turtle Beach again. They still have not released DirectX 6.0 drivers yet! (And now 7.0 is out!)

Then I went to a computer show and bought a 4MB 3D-video card for $40. The TPC came with 1Mb video, upgradeable to 2Mb. At the same time I bought a Pentium 133 CPU. I only wanted a P120, but they could not be found at the time. I also picked up an additional 16Mb or RAM, now I had a total of 32Mb.

I installed these components and noticed a big difference when playing Virtua Racing. The PC was now running at 120Mhz (per the manual) with 4Mb video.

Next I ordered the 256k external cache chip from NCR for about $60. WOW, this made a BIG difference. The cache made more of a difference than the bump from 75 to 120Mhz did.

I then found out how to set the switches to make the PC run at 133Mhz. Nice, since I had a P133 already. This again made a difference. Not only 13Mhz faster for the CPU, but the bus speed went from 60 to 66 MHz as well.

About 6 months later they started to come out with the MMX overdrive chips that were doing 240Mhz, then they came out with the 266MMX-overdrive processor. I asked my wife for a 266MMX overdrive for Christmas 1998.

I installed it and found a huge increase in speed. The MIPS rating really jumped up there. I had been doing benchmark tests, starting after I installed the 120Mhz CPU, no info on how it ran as a P75.

Then after a month or two, I upgraded to Windows 95B with FAT32. I reformatted the hard drive, and again saw a large increase in speed on the benchmark tests. Especially on the MFLOPS rating.

I went to another computer show, sold my P75 and P133 CPU’s and my 4 – 4MB RAM chips. Then I bought 4 – 8MB RAM chips. Now I have a total of 48MB of RAM.

After another month or two, the PC started experiencing problems. After checking out everything, I checked with the Overdrive manufacturer and they had me return it.

By this time they no longer made the IDT based 266MMX. They offered to give me an AMD based 400Mhz CPU. However, thanks the wonderful insight of NCR/AT&T, the proprietary nature of the machine made it incompatible. (Which is also why you can not upgrade to 512K cache or change out the motherboard, or use a standard power supply! I'm glad they are out of the PC business!)

So, they gave me a 233MMX Intel chip. I was skeptical at first, but luckily I had the benchmark tests from before. I installed the new 233MMx Intel chip and there was again an increase in speed over the 266MMx IDT chip. The increase was again more noticeable on the MFLOPS side of the benchmark.

At this point I am basically out of ideas on how to make this CPU any faster. It has reached its limit as far as I am concerned. I could get a better 3D-video card and soundcard, but that’s about it. Even so, I can still run anything I like on this system. I have not tried any high-end video games because of the video and soundcard limitations though.

The company I bought the Overdrives from was ZERUS. I have been completely happy with them. They replaced the defective CPU quickly and without ANY hassles.