EINTR.net / systems / compaq / presario433

Compaq Presario 433

I don't consider this low-cost, all-in-one computer from Compaq a proper *nix workstation. But I think it deserved this page because of the interesting form factor.

Pictures

Notes

The CPU was upgraded to an Evergreen 586 / AMD 5x86 133MHz.
- The AMD 5x86 is designed as a low voltage CPU. Incompatible with this motherboard.
- The Evergreen packaging makes the Socket 3 CPU backward compatible with the Socket 486/1/2.
- The original CPU was an Intel 486SX 33MHz (Ran NetBSD).
- I upgraded first to an Intel 486DX2 66MHz (To run OpenBSD).
- A 486DX (with FPU) is the minimum requirement to run OpenBSD/i386. OpenBSD doesn't have software floating-points.
Memory was upgraded to the maximum of 20MB from the original 12MB.
It run a slimmed down kernel to save much needed memory. OpenBSD 6.5 doesn't support this low amount of memory anymore in GENERIC kernels. This installation is non-standard and unsupported.
The network card on picture is a we0 but it gave me issues. It has been replaced by a ALN101 (NE2000 compatible, jumperless ISA card).
F10 to access BIOS.
The BIOS does not support ISA-PnP. Which means ISA cards must be set with jumpers or through vendor supplied program. The network card is manually set to IRQ5 in order to support the DOS Packet driver.
The power cord plugs in the back of monitor in such a way that it acts as a simple lock for the motherboard drawer.
The original Compaq floppy disk died. It was replaced.
The hard-drive crashed since. It was replaced with a 120GB IDE laptop drive in an adaptor.
The BIOS has limitations for hard disk size. Natively, I wasn't able to go beyond about 1GB recognized. I now use the EZ-Drive int 13h extension boot software to access up to 8GB from DOS. OpenBSD use LBA directly through the controller and can access the whole disk.

Specifications

CPU	133 MHz AMD 5x86 P75 - Evergreen 586 packaging makes it compatible with the 486 PGA Socket
FSB	33 MHz (or 25MHz) (Supports 5V CPU, Socket 486/1 compatible, running at a fixed multiplicator of these 2 speeds)
Memory	20 MB (max 20 MB - 4 MB on board + 2 x (1, 2, 4 or 8 MB FPM 72 pins SIMM 60-70ns)
Bus	16 bits ISA (not PnP) - 2 slots on a riser card
Video	Cirrus Logic CL-GD5420 512K SVGA capable (800x600: 256 colors) built-in 14" monitor with inactivity timeout.
Sound	Standard PC beeper Microsoft Sound System (do not know it's capability) [not supported in OpenBSD]
Disk Controller	1 x ATA controller [generic wdc driver in OpenBSD, standard master/slave capable] internal 40 pin male connector [single hard-disk short cable provided]
Case	All-in-One Computer 1 x 3.5 inch floppy drive 1 x half-height IDE hard-drive
External Connectors	Bottom row, from left to right: PS/2 keyboard - 6 pin mini-DIN female connector PS/2 mouse - 6 pin mini-DIN female connector COM1 serial port - DB9 male connector LPT1 parallel port - DB25 female connector Game port (joystick) - DB15 female connector COM2 internal 2400 baud fax-modem - left: line in, right: handset [factory option]

Dmesg

OpenBSD 6.9-stable (CPAQ69) #1: Thu May 13 15:06:30 EDT 2021
    root@qemu11.o37.ca:/root/src/kernels/compile/CPAQ69
real mem  = 20504576 (19MB)
avail mem = 16220160 (15MB)
random: good seed from bootblocks
mainbus0 at root
bios0 at mainbus0: date 12/30/93
bios0: ROM list: 0xc0000/0x8000
cpu0 at mainbus0: (uniprocessor)
cpu0: AMD Am5x86 W/T 133/160 ("AuthenticAMD" 486-class), 04-0e-04
cpu0: FPU
isa0 at mainbus0
isadma0 at isa0
fdc0 at isa0 port 0x3f0/6 irq 6 drq 2
com0 at isa0 port 0x3f8/8 irq 4: ns16450, no fifo
com1 at isa0 port 0x2f8/8 irq 3: ns16450, no fifo
pckbc0 at isa0 port 0x60/5 irq 1 irq 12
pckbd0 at pckbc0 (kbd slot)
wskbd0 at pckbd0: console keyboard
vga0 at isa0 port 0x3b0/48 iomem 0xa0000/131072
wsdisplay0 at vga0 mux 1: console (80x25, vt100 emulation), using wskbd0
wsdisplay0: screen 1-5 added (80x25, vt100 emulation)
wdc0 at isa0 port 0x1f0/8 irq 14
wd0 at wdc0 channel 0 drive 0: <WDC WD1200BEVE-00A0HT0>
wd0: 16-sector PIO, LBA48, 114473MB, 234441648 sectors
wd0(wdc0:0:0): using BIOS timings
ne2 at isa0 port 0x280/32 irq 5, NE2000 (RTL8019), address 00:60:67:25:b8:b8
pcppi0 at isa0 port 0x61
spkr0 at pcppi0
npx0 at isa0 port 0xf0/16: reported by CPUID; using exception 16
root on wd0a (6b51e7e6facba0d5.a) swap on wd0b dump on wd0b
fd0 at fdc0 drive 0: 1.44MB 80 cyl, 2 head, 18 sec

Jumpers Markings

Motherboard:

	P1	1-2	25 MHz
		2-3	33 MHz

	P2	1-2	PQFP	# Soldered CPU only
		2-3	PGA	# Socket 486/1 used

	P3-P4	1-2	ODP/ODPR
		2-3	SX(PGA)

	P5	1-2	ODPR	# 168 pins OverDrive Processor Replacement
		2-3	ODP	# 169 pins OverDrive Processor
		3-4	SX(PGA)

	P6	1-2	CMOS CLEAR


	Original 486SX  33MHz:	P1:2-3	P2:2-3	P3-P4:2-3	P5:3-4	P6:1-2
	Upgraded 486DX2 66MHz:	P1:2-3	P2:2-3	P3-P4:1-2	P5:1-2	P6:1-2

	Evergreen 586 / AMD 5x86 133MHz
		Motherboard:	P1:2-3	P2:2-3	P3-P4:1-2	P5:1-2	P6:1-2
		Evergreen:	WT	4X	NORMAL

Evergreen 586:

	WB	# Write-Back Cache	[Late 486 CPU and motherboard feature]
	WT	# Write-Throught Cache	[Early 486 motherboard]

	4X	# Speed multiplicator for CPU
	3X	

	OVRDRV	# Raise signal to disable the original CPU
	NORMAL