NextStep/Intel, 486's and Pentium overdrive, thoughts. - cctalk

3 Mar 2023

As part of fixing the Pro/380 I dug out and decided to get running my 
two Intel systems. These are Compaq Deskpro/XE systems. One is a 4100 
which has an Intel 486/100 (25mhz, quad clock), the other I upgraded 
with a Pentium P524T overdrive chip at 83mhz (33mhz external clock).

The P524T was an interesting duck: It's a 5 volt pentium, 32 bit 
external bus but they did double the amount of 64 bit on-chip cache so 
it can perk along quicker than one might think. Not many were sold, but 
I have one and there you go. It even has a little fan on the heat sink 
that is powered off the chip. Cute.

The Deskpro/XE's were great systems, slimline, Compaq business audio, 
QVision video interface with 2mb of RAM, IDE drive, and oddly enough a 3 
slot ISA bus. Most of the system ran at native 32 bit, so you just ran 
a slow network card in the ISA. They also had up to 32mb memory, and an 
optional memory cache card to speed things up.

The systems had issues, both on-board batteries were dead, resulting in 
me having to find, download, run (not easy) and extract a setup floppy 
for this model as you can't do the system settings without it. Not quite 
an EISA config, but similar levels of stupidity in the ISA world. And 
one of them does not seem to see the ISA bus, but not a big deal as it 
will just be a DOS floppy maker.

Anyway, finally got one of them running and decided to do some 
benchmarks. Booting NextStep 4.2, and tried out a few basic tests.

Findings:
For general booting and such the Pentium does not offer that much of an 
advantage. Time to go from login window to system quiet with 20mb memory 
(I load several apps by default) is:
486/100-121 seconds
Pentium: 120 seconds

Installing and removing the 256k cache card (an option I have one of) 
doesn't change the time much at all, maybe a second.

Boosting memory to 32mb brought that number down to 84 seconds. Moral: 
Memory matters.

Then I figured I would try a CPU intensive app: Good old NeXT 
Mandelbrot. While a true NeXT slab will kick the rear of any Intel chip 
(due to the on board DSP56001) I figured I would put the Pentium up 
against the 486/100 and running the 486 at 33mhz external bus (133mhz) 
in insane overclock mode.`So rendering the "Valley of Fear" (a complex 
subset) resulted in:

Pentium, no external cache: 36 seconds.
Pentium, external cache: 34 seconds.

Not bad, cache really doesn't do a whole lot here.

486/100, no cache: 90 seconds. Wow, that is slow.
486/133, no cache: 65s. Faster, but very slow.

So the addition of the Pentium makes a huge difference on floating point 
CPU intensive apps. I'm also guessing the extra large cache makes a 
difference as well for highly iterative loads.

With this done I can continue looking for a 5.25 floppy to see about 
making more PRO disks.