OverDRIVING the DOS Compatible Macintosh Performa

In case you were wondering how big the difference are between the Cyrix DX2 vs the Intel DX4 Overdrive on Apples DOS compatible 68k Mac from 1995, you now have the answer!

Chapters:
00:00 Intro
00:55 About the benchmarks
01:22 Getting the baselines
05:30 Installing the DX4 Overdrive CPU
06:02 System Information
06:34 3DBench
06:50 PC Player Benchmark
07:06 DOOM
08:11 Quake
08:33 Descent

Music used in this video

#RetroComputing #MARCHintosh #Benchmarks

[squeeeb]

Interesting, never heard of this 'DOS Compatible' Performa model. I had a Performa 600 back in the day, played a lot of SC2K on that! Nice video 🙂

[TAGMedia]

One of my PowerPC Holy Grails is to obtain an one of the Orange Micro Pentium DOS compatibility Cards. I've been very curious about the performance since I was a kid.

[MrDarchangelomni]

Some Cyrix chips had a slightly faster instruction pipeline than their Intel counterparts, and lots of times were faster WINGUI Office machines, there were even GUI accelerated video cards that worked better with Cyrix chips but would fall behind in floating point intensive software.

[StudioPluche]

Once had a PC back in the day with a Cyrix DX2/66 and it was clocked at 80Mhz.

[FirstLast-wecb]

My first built PC was a dx4 100. What a blast from the past. Great video.

[chadmasta]

I think LGR did a video on this Performa (or a similar one) and I recall he mentioned that performance was worse than a PC using the same cpu so I think it has something to do with the pds slot and/or having to share graphics.

[mccrh]

Love this video, excellent experiment :) Actually been wondering this for years ;)

[Spokmoppa]

Great video again, thanks for the awesome content!

[TyTytheCat]

Curious as to see if you could run Windows 95 (or maybe something further on) on this machine with the upgraded CPU. I think it'd be neat to see.

[Cardthulhu]

Hey, I've been thinking about your channel recently. Noticed you haven't uploaded in 6 months. I hope you're doing well. Thanks for the high quality content.

[heidirichter]

I thought someone would have already given an answer as to why the speed difference varied so much, and in some cases didn't seem to be an improvement, but nobody has that I can see, so here goes.

In that generation of CPU, there was a concept called the FSB or Front Side Bus. This is how the CPU communicated with the rest of the system, and all other things being equal, a faster FSB means it can communicate with the rest of the system faster.

The other concept relevant here is the clock multiplier. This is basically how much faster then the FSB the CPU operates internally, and THIS is where the clock speed is derived from.

This is where the 2 in DX2 and the 4 in DX4 come from.

The DX2 chips (both of them) run on a 33MHz FSB and have a x2 multiplier. So 33MHz externally to the rest of the system, doubled to 66MHz within the chip.

The DX4 chip runs on a 25MHz FSB and has a x4 multiplier, so quadrupled to 100MHz.

Importantly, the CPU needs to go through the FSB to interface with ANYTHING external to the CPU itself. That includes reading and writing to RAM, the gfx card, the HDD, literally everything.

The only time the extra speed of the DX4 100 can stretch it's legs, so to speak, is when that clock speed is more important then how fast it can communicate with the rest of the board.

For this reason, a DX2 running at 80Mhz will absolutely wipe the floor with a DX4 at 100MHz in most cases, as in that case the DX2 is running on a 40MHz FSB. I'm not sure what CPU options are available for the DOS card, but yes, in some cases, the effective speed of a DX4 100 will be SLOWER than a DX2 66.

But it really does depend on the application, how much cache there is inside the CPU, etc.

There is so much more to it than the clock speed the chip is rated at.

[josephfrye]

I searched for dos version of thinkin things collection one and two but unfortunately some certain Macintosh are dos or pc compatible.

[cocusar]

I don't think that the main bottleneck is the CPU itself, maybe it's the interface to the MAC and/or the graphics chip

[hartoz]

I thought the Intel Pentium Overdrive was the fastest CPU that would fit a 486 Socket.
The Pentium overdrive is a cut down P54 core in a 486 socket compatible package.
Can you try this?

[john_ace]

Why would an AMD 5x86 5V upgrade Module not work?

[RetroShare]

Please, don't make that intro to loud. I cannot play every time with the volume buttons. It's annoying.