HP 16500B - RAM upgrades

Please note - this is a very old page and is presented as-is. I no longer own a HP16500B, and can only answer questions about it from my own hazy memory. Sorry :(

Update: 2011-04-12. Someone very kindly sent me a pair of 32Mbyte 72-pin EDO SIMMs. It turns out the 16500B can go as far as 64MB of RAM! The jury's still out as to whether this speeds up the analyser in any way (it's still dog-slow over X11) but it does work. The RAM modules I'm using are IBM branded, 80ns.

Update: 2010-10-09. I've found a couple of Agilent Service Notes regarding 16500B RAM upgrades:

• When I upgrade the system RAM in my 16500 mainframe, can I use SIMMs of different storage capacity? For example, can I use a 4 MB SIMM and an 8 MB SIMM?. Answer: Yes, but the larger memory module must be installed in Slot 0 (nearest the back panel of the LA)
• Can I increase the amount of system RAM in the 16500B Logic Analysis Mainframe?. Answer: Yes, up to 16MB. P/N for the Agilent-recommended part is 1818-5623.
• How can I determine the amount of system RAM in my 16500 mainframe?. This suggests that 16500 analysers can be upgraded to 32MB, though perhaps this only applies to the 16500C.

The HP 16500B offers a few possibilities for hardware upgrades besides the expansion cards. Obviously the hard drive can be upgraded or replaced with a CompactFlash card (up to about 512MB or so), but the base memory can also be upgraded. This memory takes the form of two 72-pin, 36-bit (parity) SIMMs on the motherboard. Either FPM or EDO will work, although ideally you should use the specified HP part – the 1818-5623, also known by the part numbers A2586-60001 and C3133-7. This is a 72-pin, 36-bit (parity mode), 2M*36 memory module with tin-plated connector pins, and was used in a number of HP products… most notably some of the LaserJet printers. This makes these modules really, really cheap on the surplus market.

My 16500B originally came with two “SMART” branded modules, part number SM5361000-8 081495-18 “Made in USA”. These are 1M*36 modules, so two of these gives a total of 8MB usable RAM (4MB per stick). From what I can tell, these memory modules were sold for use in the HP DeskJet 1200…

The 16500B has some interesting quirks – most notably if you install a single 8MB RAM module, it will only be detected as 4MB. Installing two of them produces the expected result – 16MB of available RAM.

I've tested an assortment of memory modules – the results of these tests is shown below. Slot 0 is the slot nearest the back panel of the analyser.

It seems that the 16500B doesn't care if a memory module is equipped with parity logic, nor does it matter if the module is EDO or FPM (EDO modules tend to be backwards compatible with FPM). I have no idea if you could install a pair of 16MB modules (for a total of 32MB), though this would be quite useful if you had a lot of high-data-width sampling cards (like the 16555D 2-megasample logic analyser) installed.

The basic rules for memory upgrades would seem to be:

  If you want to run the machine on one stick of RAM, install it in Slot 0.
  It's probably not a good idea to run the analyser with differing sizes of RAM in different slots.
  If you insist on mixing and matching different sizes (capacities) of RAM, put the larger one in Slot 0.
  A single 8MB module will be recognised as 4MB. If you want 8MB of RAM in your analyser, you'll need to install two 4MB modules.

If you've got one of the multi-megasample logic analyser blades installed (or a pair of them chained together), then you'll no doubt have noticed how the analyser absolutely crawls when this is in use. Increasing the amount of base RAM can improve the performance of the analyser.

Upgrading the RAM is a fairly simple, though quite involved procedure…

1. Remove all of the acquisition cards (blades) from the mainframe.
2. On the motherboard (aka base board or “planar”), you'll see two right-angled SIMM slots. The one nearest the back panel is Slot 0, the one towards the middle of the analyser is Slot 1.
3. Push the two tin latches on the socket outwards to release the memory module. Tilt the module up to a 45-degree angle, then remove it.
4. Reinstallation is the reverse of disassembly. Install the new module at a 45-degree angle, push it into the socket (some modules might be quite stiff), then tilt it down until it snaps into the pins. If it won't latch into the socket, make sure the cutout is oriented to the left, and try pushing the module firmly into the socket while tilting it down.
5. Repeat for the second module, if necessary.
6. Power the analyser up without the blades and see if it boots successfully. If it does, power down and reinstall the blades.
7. Profit!!! :)