HP 5036A Microprocessor Lab

I just got this machine possessed. It is a microprocessor demonstration board based on the Intel 8085 CPU meaning that it was built for educational use and to demonstrate the capabilities of Intel's early 8 bit CPUs. According to a very few information on the web it was produced from 1978 through the early 80's by Hewlett-Packard.

First impressions:

The nice leather briefcase makes the appearance really elegant, something that is missed from new and modern equipment. Also, push buttons are built for eternity, no lifetime by design.

Technical data:

Manufacturer: Hewlett-Packard;

CPU: NEC D8085AC (Intel 8085 compatible);

CPU clock: 2 MHz using external 4 MHz crystal;

ROM: 2 KB external  SY2316 (mapped from 0x0000 to 0x07FF);

RAM: 1 KB external 2xSY2114 (mapped from 0x0800 to 0x0BFF);

Keyboard: built-in hexadecimal keyboard plus additional function keys;

Display: 6 digit LED display;

I/O: one 8 bit port with LED indicators and DIP switches;

On-board speaker;

Additional jumpers are provided to simulate circuit failures.

Note: Regarding to the ROM and RAM chips, I could only recover the manufacturer called Synertek, which was founded in 1973, bought by Honeywell in 1979, and finally closed off in 1985. Some photo on their products can be found here.

Operation:

Upon a successful boot, the message "uLAb UP" is visible on the LED displays. Storing new programs in the RAM is possible using the push button interface. These among built-in code can be run by simply pressing "Fetch Address", setting the appropriate memory address and pressing "Run". Single line execution is also possible. This is a notable example for a compact yet powerful user interface from times before LCD/TFT displays.

In order to ease learning, several built-in demos are accessible. Notable examples are:

the Rocket Launcher demo on address 0x05F9;

Display test with moving pattern on address 0x055A;

Random Tone Generator on address 0x053E;

Stopwatch on address 0x0662.

The documentation is in fact fascinating: a 450 page book entitled Practical Microprocessor is included in the briefcase. This is not only a tutorial but a complete documentation including ROM listing, schematics and some brief datasheets as well. 

HP Notebook slow while plugged in

I recently encountered a quite strange behavior of my HP 6910p computer. It became extraordinary slow if hooked on the charger. By slow I mean that Windows booting up took more than half an hour (I tested this only once :) ) and afterwards Task Manager showed 100% CPU usage for both cores all the time, no matter if no userspace program was running. This itself could have been a simple Windows issue, but essentially the same happened for a Linux Live CD, and even worse: the BIOS menu was definitely slow to respond. However if I removed the charger (so that it ran on battery), everything went back to normal. 

Realizing that this is a hardware problem I had it repaired under warranty (they replaced the motherboard), after which everything went normal for some days and then the issue reappeared. This happened during the weekend (obviously) so I had to do something. What I noticed was that by moving the cable of the charger sometimes it can be healed. So the resolution was simple: the wire is broken somewhere. But which wire? I have never noticed a power failure, meaning that only the third one in the middle can be the source of the problem. Yes, recent notebooks demand a charger with an additional line which might tell if the charger is a proper one or not. If this connection is not present then the power management of the notebook must fall back to some extra low profile rendering the CPUs slow and the computer essentially useless.

So apart from saying a big thanks to HP I only could cut the wiring open and resolder this inner wire after which I applied a plenty of thin teflon tape to prevent it from either breaking or shorting to the other ones.

Now everything is back to normal, the long-term solution however is buying a new power supply.