Memory Chips - Testing and Results

Types of memory

There were several types of memory being used when the Z88 came out. The Z88 uses static RAM. This was the only low power type but it was extremely expensive when the Z88 came out (£200 for 1M). With the demand for portable computers, the prices have fallen. The Z88 never turns itself off. It gives a pulse every 20 seconds to keep the information stored in RAM intact. There is only one way to see if different RAM chips will work with the Z88 in these different environments is to try them.

RAM Test

Cambridge Computer wrote a BBC BASIC program to test RAM.

Unless the memory is good the Z88 will become unstable, the FAIL indicator may appear in the top right-hand corner of the display or inconsistent results will occur when checking the size of the RAM with (

CARD). For example, you may have a 512K RAM card in your Z88 but (

CARD) reports that you only have 128K. Failure of the RAM falls into the following categories.

Mechanical failure - due to the contacts being dirty or from a dry soldered joint
Unsuitable memory chip - if a different chip is used it may not have the identical specification to the one previously used.

Running the BASIC program while `tapping' the RAM pack may identify a mechanical failure. Finding other errors can be difficult.

The other sort of memory failure is where certain bits of memory suffer amnesia when you are not reading or writing to the memory.

This is like when you are just storing files in the RAM.

This fault can be found with any program, (zCheck, Zip, Unzip (Z88 Forever) or SqueeZ~88 (Rakewell)) that uses checksums on files. To use it you should:-

Run the program initially so that the checksums of the files are calculated. If you are using SqueeZ~88 or Zip, squeeze/Zip a load of big files.
Turn off the Z88 and leave it alone for about three to five days.
Re-run the program to see if the checksums of the files are different or unsqueeze/Unzip all the files again. If they are, then the RAM where the file was stored is faulty.

The following BBC BASIC program tests 32K, 128K 512K and 1MB RAM cards.

This is a destructive RAM Test. All the data that is stored in the RAM card will be erased.

Download the 4 files zipped, (original instructions, two .CLI files (which do the same thing) and the memory test software from here, and then transfer them to your Z88 with a transfer program. If the CLI file is in an EPROM in slot 3,

There are two ways you can use this program.

Just running the BBC BASIC program (Ramcard.bas)
Before using the program you should save the program to EPROM as "RAMTEST.BAS" and write the following BOOT.CLI to use with it. This will load and run the program automatically after a HARD RESET is given.

#F
|EF
RAMTEST.BAS~E~E
#B
CHAIN
"RAMTEST.BAS"~E

To use the memory test, follow these steps:-


		Save onto an EPROM card the BOOT.CLI and RAMTEST.BAS files.
		Back-up all your files.
		Open the card flap Remove the current RAM card.
		The complete Procedure is as follows: 1) - Insert RAM TEST EPROM into slot 3 with no other cards present. 2) - Hard RESET Z88. 3) - When the screen prompts for the size of card to be tested, 4) - Type the size (in kB) and press ENTER. e.g. 32 512 or 1024. 5) - Open the Card Flap, insert the RAM card in Slot 1 then close the flap. 6) - Press any key to start the test. 7) - To test again, remove the RAM card and follow from item (2) again. Here are the individual steps.
		Insert the EPROM card in slot 3
		Leaving the card flap open, do a Hard Reset. Close the card flap The BOOT.CLI program will run, the memory test programs will be fetched from the EPROM card and then will start to run.
		When you get the Command line type in the number of K the RAM card is. E.g. 1024
		Insert the RAM card to be tested in Slot 1.
		Press the key until you get the "Testing . . . " message. Whilst this is testing, tap underneath the Z88 where the card is installed to expose any mechanical electrical problems with the card connector and/or any dry solder joints in the card itself.
		When the test is finished,
		Remove the EPROM pack and
		Do another Hard Reset.
		To make sure that the memory is alright, load a large text file into Pipedream and see if you can read the whole file.