RAM identification

How do I tell exactly what type of RAM I have so I can get more?

The specifications for your machine/motherboard will identify compatible memory. You can check your manufacturer's web site to see if they have online information.

Alternatively, as root you can issue the dmidecode command to get some information. In the memory section you'll see things like this:

Handle 0x0009, DMI type 5, 20 bytes.
Memory Controller Information 
        Error Detecting Method: None
        Error Correcting Capabilities:
                None
        Supported Interleave: Other
        Current Interleave: Other
        Maximum Memory Module Size: 512 MB
        Maximum Total Memory Size: 1024 MB
        Supported Speeds:
                Other
        Supported Memory Types:
                Other
                DIMM
                SDRAM
        Memory Module Voltage: 2.9 V
        Associated Memory Slots: 2
                0x000A
                0x000B
        Enabled Error Correcting Capabilities:
                None

Handle 0x000A, DMI type 6, 12 bytes.
Memory Module Information
        Socket Designation: SO-DIMM
        Bank Connections: 0
        Current Speed: 8 ns
        Type: Other DIMM SDRAM
        Installed Size: 512 MB (Single-bank Connection)
        Enabled Size: 512 MB (Single-bank Connection)
        Error Status: OK

Handle 0x000B, DMI type 6, 12 bytes.
Memory Module Information
        Socket Designation: SO-DIMM
        Bank Connections: 2
        Current Speed: 8 ns
        Type: Other DIMM SDRAM
        Installed Size: 512 MB (Single-bank Connection)
        Enabled Size: 512 MB (Single-bank Connection)
        Error Status: OK

Above you see that this machine has a maximum installed memory size of 1GB, and it has two non-ECC 2.9V 512MB SODIMM installed (it is at its maximum configuration).

the what code? is that a bash cmd line?

Yes, as root, you can issue the 'dmidecode' command (if it is supported by your hardware), and either pipe the output to less or direct it to a file. For example:

dmidecode > dmidecode.txt

So what do I have then?

Handle 0x0002, DMI type 2, 15 bytes Base Board Information Manufacturer: ECS Product Name: Alhena Version: 1.0 Serial Number: Asset Tag: Features: Board is a hosting board Board is replaceable Location In Chassis: Chassis Handle: 0x0003 Type: Motherboard Contained Object Handles: 0 Handle 0x0003, DMI type 3, 21 bytes Chassis Information Manufacturer: Type: Desktop Lock: Not Present Version: Serial Number: Asset Tag: Boot-up State: Safe Power Supply State: Safe Thermal State: Safe Security Status: None OEM Information: 0x00000000 Heigth: Unspecified Number Of Power Cords: 1 Contained Elements: 0 Handle 0x0004, DMI type 4, 35 bytes Processor Information Socket Designation: CPU 1 Type: Central Processor Family: Unknown Manufacturer: Intel ID: 64 0F 00 00 FF FB EB BF Version: Intel(R) Celeron(R) D CPU 3.33GHz Voltage: 1.3 V External Clock: 133 MHz Max Speed: 3325 MHz Current Speed: 3325 MHz Status: Populated, Enabled Upgrade: Other L1 Cache Handle: 0x0005 L2 Cache Handle: 0x0006 L3 Cache Handle: 0x0007 Serial Number: Asset Tag: Part Number: Handle 0x0005, DMI type 7, 19 bytes Cache Information Socket Designation: L1-Cache Configuration: Enabled, Not Socketed, Level 1 Operational Mode: Write Back Location: Internal Installed Size: 16 KB Maximum Size: 16 KB Supported SRAM Types: Other Installed SRAM Type: Other Speed: Unknown Error Correction Type: Parity System Type: Data Associativity: 8-way Set-associative Handle 0x0006, DMI type 7, 19 bytes Cache Information Socket Designation: L2-Cache Configuration: Enabled, Not Socketed, Level 2 Operational Mode: Write Back Location: Internal Installed Size: 512 KB Maximum Size: 512 KB Supported SRAM Types: Other Installed SRAM Type: Other Speed: Unknown Error Correction Type: Single-bit ECC System Type: Unified Associativity: 8-way Set-associative Handle 0x0007, DMI type 7, 19 bytes Cache Information Socket Designation: L3-Cache Configuration: Disabled, Not Socketed, Level 3 Operational Mode: Write Back Location: Internal Installed Size: 0 KB Maximum Size: 0 KB Supported SRAM Types: Other Installed SRAM Type: Other Speed: Unknown Error Correction Type: Other System Type: Other Associativity: Other Handle 0x0008, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J1A1 Internal Connector Type: None External Reference Designator: PS2Mouse External Connector Type: PS/2 Port Type: Mouse Port Handle 0x0009, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J1A1 Internal Connector Type: None External Reference Designator: Keyboard External Connector Type: PS/2 Port Type: Keyboard Port Handle 0x000A, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J2A2 Internal Connector Type: None External Reference Designator: USB1 External Connector Type: Access Bus (USB) Port Type: USB Handle 0x000B, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J2A2 Internal Connector Type: None External Reference Designator: USB2 External Connector Type: Access Bus (USB) Port Type: USB Handle 0x000C, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J4A1 Internal Connector Type: None External Reference Designator: LPT 1 External Connector Type: DB-25 male Port Type: Parallel Port ECP/EPP Handle 0x000D, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J2A1 Internal Connector Type: None External Reference Designator: COM A External Connector Type: DB-9 male Port Type: Serial Port 16550A Compatible Handle 0x000E, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J6A1 Internal Connector Type: None External Reference Designator: Audio Mic In External Connector Type: Mini Jack (headphones) Port Type: Audio Port Handle 0x000F, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J6A1 Internal Connector Type: None External Reference Designator: Audio Line In External Connector Type: Mini Jack (headphones) Port Type: Audio Port Handle 0x0010, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J6B1 - AUX IN Internal Connector Type: On Board Sound Input From CD-ROM External Reference Designator: Not Specified External Connector Type: None Port Type: Audio Port Handle 0x0011, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J6B2 - CDIN Internal Connector Type: On Board Sound Input From CD-ROM External Reference Designator: Not Specified External Connector Type: None Port Type: Audio Port Handle 0x0012, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J6J2 - PRI IDE Internal Connector Type: On Board IDE External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x0013, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J6J1 - SEC IDE Internal Connector Type: On Board IDE External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x0014, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J4J1 - FLOPPY Internal Connector Type: On Board Floppy External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x0015, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J9H1 - FRONT PNL Internal Connector Type: 9 Pin Dual Inline (pin 10 cut) External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x0016, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J1B1 - CHASSIS REAR FAN Internal Connector Type: Other External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x0017, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J2F1 - CPU FAN Internal Connector Type: Other External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x0018, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J8B4 - FRONT FAN Internal Connector Type: Other External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x0019, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J9G2 - FNT USB Internal Connector Type: Other External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x001A, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J6C3 - FP AUD Internal Connector Type: Other External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x001B, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J9G1 - CONFIG Internal Connector Type: Other External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x001C, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J8C1 - SCSI LED Internal Connector Type: Other External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x001D, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J9J2 - INTRUDER Internal Connector Type: Other External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x001E, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J9G4 - ITP Internal Connector Type: Other External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x001F, DMI type 8, 9 bytes Port Connector Information Internal Reference Designator: J2H1 - MAIN POWER Internal Connector Type: Other External Reference Designator: Not Specified External Connector Type: None Port Type: Other Handle 0x0020, DMI type 9, 13 bytes System Slot Information Designation: PCI-E Type: 32-bit PCI Express Current Usage: Available Length: Short Characteristics: 3.3 V is provided Opening is shared PME signal is supported Handle 0x0021, DMI type 9, 13 bytes System Slot Information Designation: PCI1 Type: 32-bit PCI Current Usage: Available Length: Short ID: 1 Characteristics: 3.3 V is provided Opening is shared PME signal is supported Handle 0x0022, DMI type 9, 13 bytes System Slot Information Designation: PCI2 Type: 32-bit PCI Current Usage: In Use Length: Short ID: 2 Characteristics: 3.3 V is provided Opening is shared PME signal is supported Handle 0x0023, DMI type 9, 13 bytes System Slot Information Designation: PCI3 Type: 32-bit PCI Current Usage: Available Length: Short ID: 3 Characteristics: 3.3 V is provided Opening is shared PME signal is supported Handle 0x0024, DMI type 10, 6 bytes On Board Device Information Type: Video Status: Enabled Description: Handle 0x0025, DMI type 11, 5 bytes OEM Strings String 1: bid=64NAhcBLA5;C_MOJ;SFCHK;LScribe;DVDP_STD;SDMED_PLS;MDVD_STD;M String 2: SENC;QUIF_NUE;MSMON_STD;AOL_MN;PROD_MSWORKS;RP_STD;IS.N60d;OEMAu String 3: ditBootLink=\\10.10.5.8\OEMAuditBootLink\CTO.cmd;.fN;## String 4: String 5: String 6: String 7: String 8: String 9: String 10: String 11: String 12: String 13: String 14: String 15: String 16: Handle 0x0026, DMI type 13, 22 bytes BIOS Language Information Installable Languages: 1 en|US|iso8859-1 Currently Installed Language: en|US|iso8859-1 Handle 0x0027, DMI type 15, 35 bytes System Event Log Area Length: 4 bytes Header Start Offset: 0x0000 Header Length: 2 bytes Data Start Offset: 0x0002 Access Method: Indexed I/O, one 16-bit index port, one 8-bit data port Access Address: Index 0x046A, Data 0x046C Status: Invalid, Not Full Change Token: 0x00000000 Header Format: No Header Supported Log Type Descriptors: 6 Descriptor 1: End of log Data Format 1: OEM-specific Descriptor 2: End of log Data Format 2: OEM-specific Descriptor 3: End of log Data Format 3: OEM-specific Descriptor 4: End of log Data Format 4: OEM-specific Descriptor 5: End of log Data Format 5: OEM-specific Descriptor 6: End of log Data Format 6: OEM-specific Handle 0x0028, DMI type 16, 15 bytes Physical Memory Array Location: System Board Or Motherboard Use: System Memory Error Correction Type: None Maximum Capacity: 1 GB Error Information Handle: Not Provided Number Of Devices: 2 Handle 0x0029, DMI type 19, 15 bytes Memory Array Mapped Address Starting Address: 0x00000000000 Ending Address: 0x038000003FF Range Size: 234881025 kB Physical Array Handle: 0x0028 Partition Width: 0 Handle 0x002A, DMI type 17, 27 bytes Memory Device Array Handle: 0x0028 Error Information Handle: Not Provided Total Width: 64 bits Data Width: 64 bits Size: 256 MB Form Factor: DIMM Set: None Locator: DIMM0 Bank Locator: BANK0 Type: DDR2 Type Detail: Synchronous Speed: Unknown Manufacturer: Manufacturer0 Serial Number: SerNum0 Asset Tag: AssetTagNum0 Part Number: PartNum0 Handle 0x002B, DMI type 126, 19 bytes Inactive Handle 0x002C, DMI type 17, 27 bytes Memory Device Array Handle: 0x0028 Error Information Handle: Not Provided Total Width: Unknown Data Width: Unknown Size: No Module Installed Form Factor: DIMM Set: None Locator: DIMM1 Bank Locator: BANK1 Type: Unknown Type Detail: Unknown Speed: Unknown Manufacturer: Manufacturer1 Serial Number: SerNum1 Asset Tag: AssetTagNum1 Part Number: PartNum1 Handle 0x002D, DMI type 126, 19 bytes Inactive Handle 0x002E, DMI type 32, 20 bytes System Boot Information Status: No errors detected Handle 0x002F, DMI type 127, 4 bytes End Of Table

It says:

Handle 0x0028, DMI type 16, 15 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: None
Maximum Capacity: 1 GB
Error Information Handle: Not Provided
Number Of Devices: 2

Handle 0x002A, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0028
Error Information Handle: Not Provided
Total Width: 64 bits
Data Width: 64 bits
Size: 256 MB
Form Factor: DIMM
Set: None
Locator: DIMM0
Bank Locator: BANK0
Type: DDR2
Type Detail: Synchronous
Speed: Unknown
Manufacturer: Manufacturer0
Serial Number: SerNum0
Asset Tag: AssetTagNum0
Part Number: PartNum0

Handle 0x002C, DMI type 17, 27 bytes
Memory Device
Array Handle: 0x0028
Error Information Handle: Not Provided
Total Width: Unknown
Data Width: Unknown
Size: No Module Installed
Form Factor: DIMM
Set: None
Locator: DIMM1
Bank Locator: BANK1
Type: Unknown
Type Detail: Unknown
Speed: Unknown
Manufacturer: Manufacturer1
Serial Number: SerNum1
Asset Tag: AssetTagNum1
Part Number: PartNum1

You have a maximum capacity of 1GB. You have a 256MB DIMM (Synchronous, DDR2, 64-bit) in slot 0, with an unused DIMM slot. Your BIOS may provide additional information on memory timing.

So to buy more I need to look for 64-bit, DDR2 DIMM?

What "PC" is that?
DDR2 RAM

PC3200
PC4200
PC5400
PC6400

Um, I am still in the dark on this...

From the above comments:

The specifications for your machine/motherboard will identify compatible memory. You can check your manufacturer's web site to see if they have online information. Your BIOS may provide additional information on memory timing.

We're in the dark on your progress too.

OK, this is what the label on my RAM says.

256mb 1Rx16 PC2-4200U-444-12

You have PC2 4200 DDR2 memory (probably 4-4-4-12 timing).