I posted the following document to comp.sys.hp48 on August 3, 1993. It is now included on Goodies disk #9. At the time, the ROM rev M was the latest available. Is there anyone out there that has a version P or R that they want to mail to me to test? :)

Here is an update to DRAIN.DOC (goodies disk #6). I've tested every operation that I could think of on an SX (rev E), GX (rev L), and GX (rev M).

The differences between the rev L GX and rev M GX were significant, so I'm putting them in separate columns. I'm sure that the main reason for the differences is the newer LCD screen used in the rev M machine. Although the new LCD screen is slower, it looks like it draws less current. There may be other hardware design differences as well, so I'm not sure if the LCD screen is actually the reason for the smaller current. I would venture to guess that any ROM version past M will be very similar to the version tested here. I didn't have time to test all functions on the version M ROM GX, but you get the general idea. It's not really useful to have a totally exhaustive list anyway. This will give you a good idea of what's going on. If anyone wants to make a more complete list, then be my guest.

Some of these current measurements may be different than in DRAIN.DOC. The batteries are to blame for this. If your batteries are fresh, then the current will be noticeably different than if they've been used for a while. I used 3 brand new Duracell AAA batteries for this test. I used the same batteries when testing all machines. All batteries measured slightly > 1.5 V each, before and after the tests. The SX used here is the same one that I used for DRAIN.DOC.

This is the current drawn from the batteries, given the operation:

Current (mA)        |
 SX:E | GX:L | GX:M | Operation
------|------|------|------------------------------------------------
  ??  |  ??  |  ??  | Coma mode [ON]-[SPC]
  ??  |  ??  |  ??  | Off
  2.2 |  4.8 |  4.3 | idle, RAM empty
  2.2 |  4.8 |  4.3 | idle, RAM full
  2.2 |  4.8 |  4.3 | idle, contrast as dark as possible
  2.2 |  4.8 |  4.3 | idle, contrast as light as possible
< 4.6 |< 6.0 |< 5.6 | idle, Clock on in status line (fluctuates a lot)
  3.3 |  7.0 |  6.2 | Command line input/Edit
  6.2 | 14.1 |  ??  | holding down [ON]
      |      |      |
  6.5 | 16.5 | 14.2 | User-RPL loop
  5.1 | 12.0 | 11.1 | fEVAL of User-RPL loop (LCD screen turned off)
  6.3 | 15.9 | 13.9 | system-RPL loop
  4.9 | 11.7 | 10.8 | fEVAL of system-RPL loop (LCD screen turned off)
  4.9 | 13.7 | 11.5 | machine language loop
  3.4 |  9.2 |  8.5 | fEVAL of machine language loop (LCD screen turned off)
      |      |      |
  6.3 | 16.3 | 14.1 | BEEP (600 Hz)
  8.1 | 17.9 | 15.7 | BEEP (6000 Hz)
  8.6 | 18.3 | 16.3 | BEEP (>= 10000 Hz)
      |      |      |
  6.3 | 16.6 |  ??  | Tetris 1.52 by Detlef Muller (sys-RPL)
  5.2 | 13.5 |  ??  | Diamonds by Doug Cannon (ML)
      |      |      |
------|------|------|- RAM CARDS ---- HP 128Kb cards ----------------
  3.2 |  6.7 |  6.1 | idle, 1 card (either port) freed
  3.2 |  6.7 |  6.1 | idle, 1 card merged
  4.5 |  8.6 |  7.8 | idle, 2 cards freed
  4.5 |  n/a |  n/a | idle, 2 cards merged
      |      |      |
------|------|------|- WIRE TRANSMISSIONS ---------------------------
  2.2 |  4.8 |  4.3 | idle, connected, IO port closed
  3.1 |  6.9 |  ??  | idle, connected, IO port open
  7.9 | 19.0 |  ??  | receiving from IBM
  7.8 | 18.4 |  ??  | sending to IBM
      |      |      |
------|------|------|- IR TRANSMISSIONS -----------------------------
  2.5 |  5.3 |  4.7 | idle, IO port open
  7.0 | 16.8 |  ??  | trying to connect
  9.8 | 18.7 |  ??  | sending to another HP48
 15.6 | 43.0 | 38.0 | (!) PRLCD (printing, no IR printer nearby)
------|------|------|------------------------------------------------

A couple of notes: Pressing ON does not close the I/O port, but turning the HP OFF, then ON, the port is closed. ( I guess the manual wasn't kidding when it said to always close the port! )

Conclusions? Well, I can say that all GX owners will be buying batteries more often than SX owners! And, if you play games, play Diamonds, not Tetris! (just kidding, Detlef :)

I placed an ammeter in series with the batteries to make these measurements. I feel that the measurements are good, since the ammeter I used has only a 250 mV maximum burden at fullscale deflection of 200 mA.

My ammeter was not capable of measuring the OFF or COMA modes, which means that they are less than 2 mA. If anyone has a more accurate device and can make these measurements, then please do, and send them to me.

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